FAQs about Cooling

  • My car heats up during warmer weather, why?
  • Should I replace my fan with an electric one?
  • How does my fan clutch work?
  • How do I replace my coolant?
  • When the temp control is in the middle I'm not getting heat in the car.
  • Should I replace my thermostat with a cooler one?
  • The heater controls are acting bizarrely, what's up?
  • How do I install a block heater?

  • My car heats up during warmer weather, why?

    Date: Thu, 1 Apr 93 07:57:23 EST
    From: Gill Watt <watt@cadsrv.enet.dec.com>
    To: swedishbricks@me.rochester.edu
    Subject: Re: b230 heating up in the warmer weather

    The B230 in my '85 245 (166k) does this too. It's been getting progressively worse over the last several summers. My current solution (recommended by my mechanic) is to swap in a "summer" thermostat that is set at a lower temperature (71 deg. C, I believe) for the summer months.

    This does something although a long hill in 5th gear will drive the gauge right up there. I also have to switch to a "winter"thermo in November or I get very little heat.

    The story I've gotten is that my radiator has become blocked with deposits and that my radiator is/has plastic and can't be recored. I've occasionally considered just replacing the radiator, but given that it still works (sort of) I can't bring myself to spend the $$$.

    Any suggestions? Ideas?


    Date: 31 Mar 93 16:47:09 U
    From: "Ed Fair" <ed_fair@msmailbo.gatech.edu>
    Subject: b230 heating up in the warmer weather
    To: swedishbricks@me.rochester.edu

    my b230's doing it's spring thing again - running hotter - no panic yet but just enough to keep me muttering and watching that gauge. lasts all summer long too. it's not worth the agony, in my opinion. anybody else in the same boat? i considered replacing the thermostat but i don't see why the ambient temperature would affect it.


    Date: Thu, 1 Apr 93 12:17:21 CST
    From: barnett@mcc.com (Jim Barnett)
    To: swedishbricks@me.rochester.edu
    Subject: b230 heating up in the warmer weather

    One think to check is the fan clutch. Fan is supposed to speed up at a rate that is non-linear with the engine speed (i.e., the higher the engine speed, the less of an increment in fan speed for each additional rpm of engine speed.) The way they handle this (at least on some models) is to have a fan clutch that is slips a bit as the fan moves faster. When the clutch wears out, it slips too much, the fan slows down, and the engine will tend to overheat - particularly when it's warm out or the engine is under stress.

    A worn-out fan clutch was the mysterious cause of my 75 245's running hot when I first bought it - I'd changed the radiator, thermostat and just about everything else before I figured it out. One problem is that I don't know of any easy way to test whether the fan clutch is worn or not - the Volvo manual gives an engine-rpm vs fan-rpm graph, but I don't know what we're supposed to do with it - watch the fan and count _real_ fast?

    - Jim

    Date: Mon, 5 Apr 1993 10:33:52 PDT
    From: damouth@wrc.xerox.com (David E. Damouth)
    To: barnett@mcc.com, swedishbricks@me.rochester.edu
    Subject: Re: b230 heating up in the warmer weather

    >>I don't know of any easy way to test whether the fan clutch is worn or not -

    At highway speeds, the fan is irrelevant. So if the car runs cool when pushing hard at high speed (say steady 85 mph), but overheats in city traffic, then the fan clutch might be suspected. If it overheats at highway speeds, the radiator is probably clogged (perhaps externally clogged with bugs - check that first). It wouldn't hurt to use a strong radiator cleaner and reverse flush. It might stave off replacing it for a while. And its a good idea to do this before putting in a new radiator anyway - any crud in the block will get flushed out rather than getting stuck in the new radiator.

    As far as I know, all thermostats fail by sticking open rather than closed. I don't think it is possible for a bad thermostat to cause overheating.

    Another famous problem on some American cars it the collapsing radiator hose: when the water pump is pulling hard, an old, soft, intake hose can collapse, blocking water flow. When you examine it at an idle or with the engine off, it looks normal. I don't know if the Volvo hose geometry makes this likely.


    Date: Fri, 14 May 93 11:41:44 CDT
    From: barnett@mcc.com (Jim Barnett)
    To: dk010b@uhura.cc.rochester.edu
    Cc: swedishbricks@me.rochester.edu
    Subject: thermostats/fan clutch

    As I understand it, the car will run hot if the thermostat gets stuck closed and cold if it gets stuck open. I don't know which kind of failure is more likely, but both are possible. My 89 240 was running just a touch cold - putting in a new thermostat (rated at the same temperature) fixed it (so the thermostat must have been opening a bit too early.)

    Another thing to check for if your car is running hot is a slipping fan clutch - 13 years is plenty of time for it to wear out. My 75 245 had that problem a couple of years ago and replacing the fan fixed it.

    - Jim

    Date: Fri, 14 May 93 14:09:51 CDT
    From: barnett@mcc.com (Jim Barnett)
    To: watt@cadsrv.enet.dec.com
    Cc: swedishbricks@me.rochester.edu
    Subject: slipping fan clutch

    In my case, the overheating due to fan slippage was most noticeable at idle - at higher speeds, the air blowing by provides a lot of cooling.

    - Jim

    Date: Mon, 17 May 1993 07:10:41 PDT
    From: Raphael_F._Bov.wbst311@xerox.com
    Subject: Re: slipping fan clutch
    To: watt@cadsrv.enet.dec.com
    Cc: swedishbricks@me.rochester.edu

    Another (series of) thought(s) on your overheating problem...

    It seems that your cooling system capacity is low. High speed and high load certainly produce maximum heat. But there is lots of air available at high speed, and thus the fan shouldn't be a factor. This points to: - low water pump flow rates- the water's not circulating fast enough to take all the heat away (possible but doubtful; pumps usually leak and hoses don't get blocked, but there's always the thermostat that won't open all the way) - low radiator air flow rates - the vanes between the tubes are blocked with bugs, etc. (you can tell by looking; if you don't see light when viewed perpendicularly from the front with the hood open, or see lots of 6-legged road kill, that may be the problem) - low radiator flow rates- the water's not getting through the radiator fast enough (possible, especially in connection with poor thermal conduction, below) - poor thermal conduction between the hot water flowing quickly throught he radiator and the high volumes of cool air flowing through the openings between the vanes on the radiator tubes due to corrosion buildup on the inside of the tubes, also reducing water flow.

    My experience would point to the last 2, both of which are cured by radiator recoring, $60 or so at a local radiator shop. We did this on the '81 244 at about 120K miles, because it had sit for it's first year, then been driven by "short-timers" followed by ownership by a then-ignorant-of-coolant-aging owner, yours truely. If the brick hasn't had the coolant changed about once every other year, this may be your culprit. We also have an '85 245 at 160K+ miles (didn't look this AM) that's had no cooling problems (knock on nearest wood; head will have to do since desk is metal) presumably because it's coolant's been changed every couple of years.

    If there was some way to monitor temperature at the cold side of the radiator, like on the water pump inlet hose, you'd be able to tell for sure. If that water isn't getting hot while the engine is, look elsewhere, like a partially opening thermostat.

    Good Luck


    Date: Mon, 17 May 93 10:39:59 EDT
    From: Gill Watt <watt@cadsrv.enet.dec.com>
    To: swedishbricks@me.rochester.edu
    Subject: overheat solved - apology


    Well, over the weekend (after finally aquiring a drain pan of suitable capacity), I drained my cooling system ('85 245, 167k) and removed the radiator to see if it might be the culprit as suggested by several people.

    Upon closer inpection (it's hard to see the front of the radiator through the AC condenser) I discovered that the front of the radiator closely resembled a vacuum cleaner bag in need of changing - i.e. so full of dirt it would hold no more. I cleaned it out with a home-use high pressure sprayer (garden hose and thumb) and reinstalled


    A long drive to EAWRC (rowing) in the other corner of CT confirmed that I should have done this long ago and spared you all the bandwidth.

    My only disappointment in this whole matter is with my mechanic (Volvo-only independent) who told me that the solution to the overheating was a cooler thermostat. Anyone want an 71 degree C or 81 degree C thermostat? Now that engine runs cool and stays cool I'd like to get a real thermostat (91 deg C) back in.

    Once again, thanks for all your help.



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    Should I replace my fan with an electric one?

    From: Shel Hall <76701.103@compuserve.com>
    To: "Volvo.net" <swedishbricks@me.rochester.edu>
    Subject: re: Mechanical fans vs. Electrical


    Dave Munroe (dmunroe@hpvclmun.vcd.hp.com) asks ...

    >>> I've thought about replacing the fan with an electric one but I don't know what the tradeoff are. A few questions:

    - Which type of fan would be more reliable?<<<

    IMHO, the mechanical one. The electrical one includes wiring, connections, a relay, a fuse, various sensors, and a motor, any of which can fail. With the mechanical, you only have to worry about the belt and the fan clutch.

    However, the electrical one can be reliable enough; I think _all_ the sidewinder-engine FWD cars use electrical fans only.

    (Trivia contest!!! Can anyone name a transverse-engined, front-wheel-drive car that had an engine-driven fan? For extra points, name a few other odd things about the arrangement on that car.)

    >>> - How much does the Volvo fan & clutch assembly weigh? <<<

    About the same as the electric one of the same size, I'll bet. I don't think the weight diffo would be interesting on a car the size of a Volvo.

    >>> - How much less of a load on the engine would an electric fan be (in


    Depends on the size of the electric motor, I'd guess. I'm no electrician, but the _starting_ load on the electric "helper" fan in my BMW is over 20 amps, though the steady-state is less than 15 amps. 15 A at 12 V is 180 Watts, and 1 HP = 746 Watts ... but this doesn't take into account the loss in generation, conversion, battery charging, etc.

    It's less that an engine-driven one, though.

    Conventional wisdom is that a solid-bolted fan is about 4 or 5 HP at highway speeds, and a viscous-coupled one is 0.25 to 4 HP depending on amount of clutch slippage. In theory, on the highway, the power drain of the clutch-coupled fan is very low, since it is operating in air that's moving pretty good, anyway, and (in the case of a heat-sensing clutch) is mostly disengaged.

    Probably the most important part about the electric fan is that it puts _no_ load on the engine when it isn't working, and can be turned on and off by any number of independent sensors or manual switches, including some that work when the engine is off.

    A typical modern setup has one or two fans, each with high and low speeds; some cars do this with resistors and relays, some do it with relays that change the fan wiring from series (low speed) to parallel (high speed). Generally, one fan will come on when the A/C is switched on, though in some cars it only works when the compressor clutch is engaged. In any case there are one or more temperature sensors that turn on more fans (or turn them up to faster speeds) when the engine gets hotter.

    My Volvo Diesel has a solid-bolted fan (feh!), and no electric fan, but my BMW has an electric fan with a couple of sensors and works this way:

    Engine cold, A/C off fan off

    Engine cold, A/C on fan slow

    Engine hot, A/C off|on fan high

    The car also has a temperature-sensing viscous fan clutch. I've installed an additional circuit that turns the fan on for a short period of time if the engine is overly hot, even with the ignition off.

    Some cars now combine things a bit, and have engine-driven fans that use and electrically-actuated clutch rather like the A/C compressor clutch. This has the advantage of responding to multiple sensors, but obviously can't run when the engine's off.

    Most "aftermarket" electric fans come with one-speed temperature- sensitive setups, but it's easy enough to rig a two-speed arrangement, an A/C interconnection, and a manual override switch. You could even get really creative and rig up a "flapper" switch that cut off the fans when there was sufficient "natural" airflow.

    A few years ago, on a trip to Florida, a bolt sheared and the whole fan/clutch assembly departed from my BMW at speed. I thought we'd run over a 'possum, so I didn't stop. In any case, a subsequent underhood inspection showed that the fan was gone, but had caused no damage when leaving.

    Since BMW fan assemblies aren't exactly thick on the ground at midnight in Valdosta, Georgia, I drove on. The lack of a fan had absolutely no effect on the highway, so we made our destination without problems.

    The next day I rigged up a manual override on the "helper" fan, rerouting a wire from the fog-light circuit so I'd have a dashboard switch to turn the fan on if the normal circuit didn't work to suit me. The whole setup functioned without incident for the whole vacation, even though the "helper" fan was never intended to be the primary cooling fan.

    75% of the energy in the fuel you burn is dissipated as heat, either from the radiator, the block, the oil pan, or out the tailpipe, so getting the cooling balance right is pretty important.


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    How does my fan clutch work?

    Date: 24 Jul 93 02:51:18 EDT
    From: Shel Hall <76701.103@compuserve.com>
    To: "Volvo.net" <swedishbricks@me.rochester.edu>
    Subject: How do fan clutches work?


    Dave Teichholtz (davet@ksr.com) asks a "Question about fan clutch" ...

    >>> How do these clutches (clutchi?) work? Is the fan clutch fluid supposed to get thicker with heat, and therefore drive the fan at the proper speed?<<<


    The non-heat-sensitive type are just a fluid coupling, and dissipate as heat some of the power (torque) input to them, through simple inefficiency. The more torque, the more slip.

    The heat-sensitive ones are much more interesting. They are actually a low-grade form of variable torque convertor, somewhat like the one that transmits the power from your engine to your automatic transmission. The amount of fluid-coupling slippage inside the unit is controlled by a valve, and the valve is, in turn, controlled by a bi-metallic element on the front of the clutch.

    When the bimetallic element gets hot, it closes the valve and that diverts more of the fluid from the slip path to the drive path, reducing the inefficiency of the clutch and increasing the fan speed.

    Now, the big problem with any engine-driven fan is that it runs slow when you need it to run fast, and runs fast when you don't need it at all.

    Specifically, at idle, with the car stopped, there is no relative wind created by the car's movement, and the fan's only ticking over, so it doesn't pull much air.

    On the other hand, when you are ripping down the road with the relative wind hustling through the grille at, oh, 54.9 MPH, the fan isn't doing anything much, no matter what the clutch does.

    The first condition (low flow at idle) is the reason so many car have helper fans that boost the flow over the A/C condensor, and the second condition is why fans that can be shut completely off are more efficient.

    BMW once tried to combine all this into one unit; my 1972 Bavaria had a temperature-sensing _friction_ fan clutch. Imagine the perverted result of the union of a drum brake and a coolant thermostat and you will have it. In theory, it would be either fully engaged (when hot) or fully released (when not.) In reality, they wore out anually, since the thermostatic element couldn't "snap" quickly enough, and they spent too much time in a half-engaged condition.

    I've been thinking about changing the Diesel over to an electric fan for several years, maybe this discussion will finally make me do it.


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    How do I replace my coolant?

    Date: Fri, 17 Sep 93 10:00:15 PDT
    From: maj@frame.com (Michael Jue)
    To: swedishbricks@me.rochester.edu
    Subject: Re: changing coolant

    Never had to do it recently, particularly due to the anti-dumping laws around here (thankful to our legislators for doing this, I like the SF bay...) I leave it to the service guys who can recycle/dispose of the old stuff cleanly.

    A couple of things on the subject:

    1. If you are flushing it yourself, don't drain it in the gutter, as above.) Thanks.

    2. Be careful on the type of cleaner used. The old, super caustic radiator flushes used to work fine BUT, a recent netter had some problems with his aluminum/plastic tank radiator leaking and while I did not have any empirical evidence supporting my theory, I strongly suspect that some of these flushes might be armful to the bonding agent between the aluminum cooling rows and the plastic tanks. Any chemists aboard who might corroborate?

    3. If you're going to the coolant route (one might wonder why I say that because isn't that the de facto standard? Read my next statement...), then the only difference between the Volvo and Prestone/Xerex/you-name-the-store -brand coolants is the cost. They are all fine quality formulations of ethylene glycol. Some of them vary as to the composition mix (%age wise) but they all do the same job.)

    I have heard many good things about Redline's "Watter Wetter", an additive for the cooling system that purportedly, well, does a better job than water/coolant alone. (Honestly, I forget exactly what it's supposed to do but it sounded good when I read about it in reports and on the net.) I believe it goes in with straight water. Racers love the stuff because if someone blows a radiator on the track, the resulting liquids deposited on the roadway are not slick like coolant. I can look into this further unless other netters can chime in with their observations/thoughts.


    Date: Fri, 17 Sep 1993 11:09:15 PDT
    Sender: Raphael_F._Bov.wbst311@xerox.com
    Subject: Re: changing coolant - additives/surface tension/nits
    To: maj@frame.com
    Cc: swedishbricks@me.rochester.edu


    Just to pick (one of my favorite) nits . . . it's Zerex and Xerox. (see above net address)

    Sorry, Mike, I couldn't resist!!

    >the only difference between the Volvo and Prestone / Zerex/you-name-the-store-brand coolants is the cost

    Then the only reason to change coolant would be to spend money needlessly. In fact, coolant contains an additive package to reduce/prevent corrosion that's especially important in our iron block/aluminum head engines. Change every 2 years and your system stays clean. Neglect it and get your radiator recored, as we did.

    > have heard many good things about Redline's "Watter Wetter", an additive for the cooling system that purportedly, well, does a better job than water/coolant alone

    Water Wetter reduces the surface tension of water, allowing it to do a better job of wetting the surface of the cylinder head, where most of the heat is. At the very surface, the head is hot enough to evaporate a thin layer of water, producing an insulator. The better the contact, the better the coolant can remove the heat, the harder it becomes to form this insulating layer of steam; the bubbles just collapse.

    Just look at how much better pure water beads up on your hood than soapy water does. Just float a pin in a dish of water (using surface tension) then add a speck of soap and watch the pin sink. You get the idea.

    I'll eschew the lengthy explanation on why water is a better coolant than antifreeze/coolant mix. And why water + Water Wetter is about the best you can get. Suffice it to say that the heat capacity of water is higher than coolant/alcohol.


    PS Are there collection stations for used coolant like ther are for waste oil?

    PPS More Water Wetter info on request.

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    When the temp control is in the middle I'm not getting heat in the car.

    Date: Wed, 22 Nov 95 13:47 MST
    To: swedishbricks@me.rochester.edu
    From: Bob Simms
    Subject: Re: Cooling problems?

    At 10:20 AM 11/22/95 -0500, you wrote:
    >With the on set of winter, I have begun to notice two things about my Volvo's
    >cooling system. BTW the car is a 1991-744T sedan.

    >The temperature indicator use to sit smack in the middle. I now notice that
    >it is a bit left of center, indicating that the engine is cooler than "normal"
    >even after running for 1/2 hour or just idling in my garage.

    >To get any heat in the cabin, I need to have the temperature control turned
    >all the way to the right. When the setting is in the middle, I don't get
    >much heat at all. I remember that I use to get way to much heat when the
    >setting was in the middle.

    >The car has 113K (Km) and was flushed during the Volvo service schedule which
    >I assume was around 60K-80K. I am temped to have the system flushed. Will
    >this cure the problem? Could it also be a water pump problem? There is no sign >the engine is overheating and I also don't push this car that much.

    Just had the same problem. Replaced the thermostat, it's was opening to soon and not keeping the engine warm enough in cold weather.

    Bob Simms
    Idaho Power Company
    Boise, Idaho
    Ph: 388-2645
    Fax: 388-6910
    E-Mail: rgs2645@idahopower.com
    Home: rgsimms@rmci.net

    From: Mark_M._Hoffman.wbst102a@xerox.com
    Date: Wed, 22 Nov 1995 11:38:55 PST
    Subject: Re:Cooling problems?
    To: lam@hyper.com
    Cc: swedishbricks@me.rochester.edu

    Hello Edmund & Brickophibes,

    Been ther. Done that on my1989 744 iT. It's your thermostat. Flush the system. New thermo & coolant. Gaurantee you'll have heat to turn Sweden into a tropical paradise.


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    Should I replace my thermostat with a cooler one?

    Date: Thu, 23 Nov 1995 04:33:51 -0500
    From: cq168@freenet.carleton.ca (Paul Grimshaw)
    To: Joseph.Rosse@colorado.edu, swedishbricks@me.rochester.edu
    Subject: Re: Cooling problems?
    Reply-To: cq168@freenet.carleton.ca


    Like other manufacturers, Volvo tends to fit slighly warmer thermostats to their cars as they leave the factory for several reasons:

    (1) Better fuel economy (as you pointed out); and
    (2) Reduced emissions.

    Upon replacement owners are faced with a choice. Shall we replace the original 197F/92C fitted to our 140-700-series cars or opt for a cooler 189F/87C, or in the case of V6s, go even cooler still to 180F/82C?

    Good question!

    Fitting a slightly cooler thermostat will give the cooling system a little more "overhead" to work with when operated in high ambient temperatures. Neveertheless, cylinder head temperatures will be reduced during all operations. Sounds good, right? Well, in a way.

    Going too cold on a thermostat setting can create unnecessary wear as the engine oil never reaches the temperature necessary to boil-off accumulated water deposits (from condensation). Furthermore, reducing cylinder head temperature too much can cause deck warping as the differences between the combustion chambers (block and head) and the surrounding metal are of a greater difference. These problems, however, will only occur in a car which has either:

    (1) no thermostat; or
    (2) A defective or radically-low thermostat

    The thermostats offered by Volvo, while cooler, are unlikely to cause any of the aforementioned problems. They will allow your engine to run *slightly* cooler, without the risk of running too cold. True, fuel economy may drop by a small amount (I would be surprised to see more than a few tenths of a mpg drop) and there may be a slight rise in CO, but there should also be a corresponding drop in NOx.

    You will note that there are three thermostat ranges offered for V-6s. This may be to offset any cooling difficulties. To say that this an inherent problem with these cars would only invite flaming by Dr. Tim, but the inference is there (by Volvo, not me!).

    Also of interest is that *no* alternatives are offered for 850/960. They come with one thermostat range (each) only.


    This does not make sense because eventually, the thermostat will be unable to overcome the lack of cooling provided by a plugged rad and/or crud-filled water passages. Should a cooling fault be present, a flush or, if unsuccessful, a new radiator is the way to go...... this may be the time to upgrade to a HD unit!

    BTW. Change coolant annually and mix coolant with distilled water (or if you can get it, de-ionized water). Deposits will be less and the system will be much happier. Change thermostats every 4 years. It beats getting stuck at the side of the road with an otherwise well-functioning brick.

    Paul Grimshaw
    The Gothenburg Bible
    34 Ullswater Dr
    Nepean, Ontario, CAN
    K2H 5H2
    E-Mail: cq168@freenet.carleton.ca

    P.S. The OE range of thermostats will continue to allow adequate cabin heat in the winter. I run the 189F/87C thermostats in both of my 240s. No fuel economy or lubrication problems, and plenty of cabin heat (even at -40F/-40C).

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    The heater controls are acting bizarrely, what's up?

    Date: Mon, 27 Nov 1995 07:43:12 -0400 To: "Gerber, Gary" From: mackinto@oasys.dt.navy.mil (David Mackintosh) Subject: Re: Disobedient Heater Controls

    >The heater controls on my '84 245GL are acting bizarrely. Sometimes when
    >I turn on the heater it works, but when I turn it off hot air keeps
    >coming out of the vents. Then, if I turn on the a/c, the heater does in
    >fact shut off and stay off.

    I had similar symptoms, the slide lever to control the temperature didn't do anything. Sometimes I'd get warm air, mostly cold, though.

    >Aren't the heater controls vacuum-operated in this puppy? I think they
    >are, and therefore suspect a vacuum leak somewhere. Can anybody offer
    >any advice as to where to check and/or what might be wrong?

    The floor/defrost/recirculate buttons are vacuum, but that only controls where the heat is directed.

    The temperature slide lever pulls a cable which opens and shuts a valve on the hose leading from the engine block to the heater core. On my car, the cable had become detached from the valve and a spring holds the valve closed. Strangely, when first turning the blower on, some warm air would come out of the vents, but it would cool off after a few minutes. I suspected a bad heater core or control valve but thankfully it was just this loose cable.

    Remove the left-side console cover (next to the driver's right foot) and trace the cable and housing (just like a bicycle cable) from the slide lever to the control valve. Apparantly it is quite easy for the cable to slip or come off completely.

    The Volvo heater is the best of any car I have ever ridden in. The independantly closing dash vents are great, too, as I can't stand as much heat as my wife claims she needs to be comfortable.

    David Mackintosh '92 Sovereign '95 Moda '82 245 Turbo '89 Hawk GT
    mackinto@oasys.dt.navy.mil Germantown, MD, USA WVC #M141 DoD #1360

    From: "Gerber, Gary"
    To: "'Volvonet'"
    Subject: FW: Disobedient Heater Contro
    Date: Mon, 27 Nov 95 08:56:00 PST
    Encoding: 72 TEXT

    Tom Biggs (among others - thanks all!) was nice enough to send me this very thorough answer to my question, and asked me to forward it to the Bricklist. So here it is:

    >The heater controls on my '84 245GL are acting bizarrely. Sometimes when
    >I turn on the heater it works, but when I turn it off hot air keeps
    >coming out of the vents. Then, if I turn on the a/c, the heater does in
    >fact shut off and stay off.

    >Aren't the heater controls vacuum-operated in this puppy? I think they
    >are, and therefore suspect a vacuum leak somewhere. Can anybody offer
    >any advice as to where to check and/or what might be wrong?

    Gary, as far as I know, the heater valve (the one that admits hot water to the heater core) itself is operated by a cable which is connected directly to the heat control lever on the dash. (Actually, the cable moves a lever on the valve that works in conjunction with a thermostat there that actually regulates the valve [so the temperature from the heater remains fairly constant as coolant temperature varies]). The valve is inside the console, not very far from the gas pedal. The little "copper wire" which runs from the valve into the airbox is actually a thermo-conductor connected to the thermostat on the valve, and is used to sense the heat level of the air that has already gone through the heater core.

    What is operated by vacuum is the air routing flaps - the defrost, floor, and recirc buttons on the dash enable vacuum to the little vacuum servos that move the flaps within the ductwork.

    It is a bit confusing as to why the heat shuts off when the A/C comes on. If I were to guess, I would guess that the heat control valve has gotten corroded or worn, and is starting to stick, leading to erratic control. I hope you gathered from my confusing description, the idea that the heat setting on the dashboard is sort of a "suggestion" to the valve but it is the thermostat itself that really operates the valve directly.

    It is possible that the sudden transition of temperature resulting from engaging the A/C is providing a "nudge" to the thermostat valve control, unsticking it and allowing it to close.

    Replacing the valve is fairly simple. Drain the coolant first though, otherwise it will flood the driver's side floor! Some coolant will come out anyway when you disconnect the hoses, so be ready for it. Remove the console side panel on the driver's side. Look for one gnarly little valve where the heater hoses, thermo-conductor "copper wire", and cable from the heat control, all converge. The only somewhat tricky bit is putting the new thermo into the heater housing. After that it is all pretty simple. Make sure that the control cable doesn't have too much slack in the "off" position or you won't get as much heat as possible in the "full on" position. That's about it.

    Tom Biggs DoD #1146 tom.biggs@dscmail.com
    '77 KZ650 "Kawaski" '81 245DL '85 245DL
    "The ultimate result of shielding men from the results of folly
    is to fill the world with fools"

    P.S. Could you please forward this to the list? Many of my postings have been getting "bounced" lately...

    * SLMR 2.1a * A clear conscience is most often a sign of a bad memory.

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    How do I install a block heater?

    Subject: Re: How to install block heater?
    Date: Thu, 14 Dec 1995 01:01:08 +0100
    From: Jon-Erik Oberg
    To: V093P9MD@ubvms.cc.buffalo.edu
    CC: Mailing list Volvo

    At 12:23 95-12-13 -0500, V093P9MD@ubvms.cc.buffalo.edu wrote:
    > I purchased an engine block heater for my '84 240 at Volvo
    >Openhouse. The unit is old new stock, the box is complete, but the
    >directions are a bit vague. It tells me to install the heater in the
    >right rear plug. I take it that it's the one under the exhaust manifold,
    >nearest the firewall. It installs in the location of the freeze plug.
    > The question is, how do I get the freez plug out without running
    >the risk of damaging anything? Any help would be greatfully accepted.

    Just drill a hole in the middle of the plug, put a screwdriver in (or something else that fits in the hole) and bend the plug out. Sounds easy? Just wait until you try to get your drilling machine in the right position.........


    Jon-Erik Oberg
    Volvo 164 Club of Sweden


    164E '75 - B30F, M410
    164E '75 - B30F, BW35
    164 '73 - B30A, M400
    242 '75 - B20F, M46

    Subject: Just put in block heater
    Date: Wed, 3 Jan 1996 14:52:28 -0500
    From: BPeter5629@aol.com
    To: swedishbricks@me.rochester.edu

    Over the xmas holidays I installed a block heater on my 1982 244 dl w/ b21f. I used the volvo block heater and here are my observations. First, people recommended using a large screwdriver to poke a hole in the freeze plug which happens to be the last one on the right side. It also happens to be behind the exhaust manifold which makes it extremely hard to access. I would be interested in knowing whether people have gone to the trouble of removing the manifold/exhaust pipe which would make access to the freeze plug much easier. If people don't do this I might suggest it but one risks complications of rusted bolts broken studs and the like. Anyway, since one was not supposed to drill throught the freeze plug, I drilled a starter hole then used a dent puller (slide hammer w/ screw tip). came out easily then. However, installation was difficult due to lack of access due blocking by the manifold, but I ended up getting the screw tightened using a screwdriver tip in a 1/4 socket in a 1/4 ratchet. The ratchet action was essential in tightening this screw in the tight spot. Lastly, I would say the cord supplied with the heater is too short if one routes it around the engine compartment rather than over the top. Now I'm just waiting for cold weather

    Brian Peterson
    80 264 GL diesel for sale 100k
    82 244 dl 135k
    89 245 dl 83k

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