Engine Starting, Charging
Maintenance FAQ for 7xx/9xx/90 Cars
and Solenoid Problems. When troubleshooting the starter, pay close
attention to the wire/cable connections. The starter needs a healthy shot
of juice to get going so you need to clean all contacts. Just because they
appear OK when the starter is not engaged doesn't mean that they are good
enough to do the job. Check ground straps. Make sure your fuses are clean.
Check any other device on the starter circuit (if any).
Make sure your battery is
OK - turn your headlights, fan, rear de-mist etc. all on and check the
voltage - should be at least 11V. If it's less than 9 or so you may not
have enough power to turn the engine over.
Test the battery terminals - should be
clean and tight. If your starter won't turn I'd remove and clean them,
then coat them with some Vaseline and put back. Also test the connection
between the wires and the terminals - again, should be tight and clean.
The usual symptom of loose connections here is that the starter solenoid
'clicks' but the engine doesn't turn.
Test the + wire (the big thick one) connection
on the starter. Again, this should be a good connection. The starter draws
several hundred amps, and a connection that's not 100% is quite likely
to drop most of the battery voltage across it.
Make sure the starter is bolted to the
engine properly - the current goes through the starter and block. Also
make sure the engine is grounded - it should have a big earthing strap,
or sometimes the battery - terminal is connected directly to the block
- either way, make sure the contacts are good.
If all of the above check OK, simply put a
wire from the battery + to the starter - connect it to where the thin wire
goes. This should make the engine turn over (but not start unless the ignition
is on). If the engine turns, it means that you have a problem in the wire
between the ignition switch and the starter; If it doesn't, the starter
is faulty: If you don't hear a 'click' the solenoid is to blame, otherwise
the starter motor itself.
Getting Weak. [Symptom:] The alternator on a 740T / B230 engine is
getting weaker, slowly but surely. What to do? [Diagnosis:] Could be all
it needs is a set of brushes. Remove the regulator/brush set from the back.
Drill out the brush wire with a 1/16" bit where it is soldered to the brush
holder. Brushes are available from Volvo for less than $4.00 (probably
part number 1362710 for your car- they can check). Solder in the new brushes
and replace the regulator/brush assembly. Also: Often the failure of an
alternator is the result of a blown diode or a worn out bearing, etc. These
parts are not expensive and their replacement is not difficult with the
right tools. ($300+ alternator replacement cost for a burned out $10.00
part, what a scam!) With a little looking, I found a shop in my area that
repaired the alternators (new bearings, brushes, leads, whatever else was
needed) for about $50. All I had to do was get the alternator out of the
car and bring it to them. This may be a way to go for you car.
If you have flickering instrument panel
warning lamps, see Warning
Lights Flickering: Bad Alternator Brushes for a solution.
Alternator Diodes. [Tip from Corey Glassman, “Electrical, Charging
and Starting System Tips and Techniques”, Underhood Service, Sept
A Digital Multi-Meter's (DMM’s) accuracy
and digital display make regulator/alternator diagnosing and adjusting
easy. Be aware that many of the tests mentioned in this article may not
work on your specific application. Some alternators can be damaged by full
fielding for instance, others have a pulse width modulated field controlling
charging. When in question, always follow the manufacturer recommendations.
An alternator generates current and voltage
by the principles of electromagnetic induction. Accessories connected to
the vehicle’s charging system require a steady supply of direct current
at a relatively steady voltage level. You cannot charge a battery with
alternating current, so it must be rectified to direct current.
Checking Ripple Voltage
Ripple voltage or AC voltage can leak
past the rectifier bridge diodes and actually cause the battery to discharge.
It can be measured by switching your DMM to AC and connecting the black
lead to a good ground and the red lead to the "BAT" terminal on the back
of the alternator. Do not connect the leads to the battery, as the battery
will absorb or "dampen" some of the AC. Run the engine at 2,000 rpm
and read the meter’s display.
You may want to also load the system by
turning on the rear window defogger and headlights. A good alternator should
measure less than 500 mV (.5 VAC). A higher reading indicates damaged alternator
diodes and may cause problems in the ECU.
Use the Vehicle’s Radio to Check Alternator
Have you ever heard a whine from the radio
that changes with engine rpm and isn’t rap music? You can use the vehicle’s
radio to test the alternator’s diodes. Turn on the radio and select a quiet
FM radio station. Turn up the volume and rev the engine from idle to 2,000
rpm and back down to idle. Listen for a small whine or "siren" noise in
the background that follows the rpm change. The noise usually indicates
excessive ripple or AC voltage leakage from the rectifier bridge diodes.
Be aware that some newer vehicles with
high energy charging systems may have a little alternator whine under normal
conditions. If your customer complains about this noise, adding a capacitor
or alternator filter may minimize it.
Verifying a Good Alternator
The battery must be fully charged before
testing the alternator. Run the engine and verify that the no-load voltage
is 13.8 to 15.3 V. Next, load the alternator to its rated output current
with a carbon pile across the battery. If you don’t have a carbon pile,
load the alternator by turning on as many accessories as you can. Run the
engine at 2,000 rpm and check the current output with a current clamp.
You may find that someone has put a number of additional loads on the charging
systems increasing current demand from the alternator. Make sure that the
alternator is rated to the application.
Where Is the Best Ground?
Technicians ask me this all the time.
With the engine shut off, the battery supplies power to accessories and
is the source of the best ground. After the engine starts and the alternator
takes over, the alternator becomes the source of all power and the battery
becomes a load and stabilizer. The best ground now is on the alternator
case, located at the grounding point for the brush set, rectifier bridge
and in some cases, the regulator. Where are they mounted? On the rear case
half, and how is the rear case half attached to the front? Typically with
four through bolts sandwiching the field between them. Most alternators
use the front case half as the mount for the belt adjusters and block attachment.
With the engine running, it is always a good idea to measure a voltage
drop between the front and rear case halves to ensure great connections.
Alternator/Battery Voltage. [Hints:] Don't trust your volt meter in
the instrument panel ! Always check voltage at the alternator & battery.
If that alternator is weak you'll notice a drop in fuel economy because
the fuel system tends to go rich as a battery dies. I replace around 40
voltage regulators in a year, and maybe 2 alternators. Be careful of chain
repair operations, gas stations and tow-truck operators: Pep boys technician
: "I'll do a quick battery test." Technician disconnects battery with ignition
on and engine at high idle . Result: INSTANT $865.00 DAMAGE, blowing five
relays, radio and other electrical equip. NEVER disconnect battery with
Juice from Alternator: Not Charging? [Query:] Well-I just put
a new battery in my 88 745ti. First-I thought it was the battery-volt
gauge was reading to the far left, almost off the gauge so i replaced
the battery. the local shop tested the car-said the charging system
was in good shape, but now, the volt gauge reads in the middle (normal)-but
when i turn on my lights/heater/whatever it goes back to the beginning
of the red zone on the far left, could it be the alternator? sometimes
its in the middle-normal, and sometimes its not, is it the alternator?
[Response: Danny Halamish]
It sounds like it's probably the charging system. Here's what I would check
(in this order):
1. Battery terminals - clean? Good connection?
2. Alternator (thick) wires - both plus
and ground (if fitted) - make sure they are OK.
3. Alternator brushes - if they are nearly
dead, this can cause this.
If all that checks out OK, I would suggest
you get a volt meter, and when the voltage reads a little low, measure
at the alternator: It should be 14.4V. If it's much less, rev it
up a little - does the voltage go up? If not, there is a problem.
Also, with the engine running and the voltage low (i.e. when the problem
happens) measure the following:
1. Voltage between the alternator power
terminal and the battery "+" terminal should be well under 0.2V
2. Voltage between the alternator body
and the battery "-" terminal should be well under 0.2V
3. Voltage between the battery "-" terminal
and the engine block should be well under 02.V
If all this checks out but you still have
a problem, the alternator voltage regulator may be defective. [Response
2:] The alternator, more specifically your built-in voltage
regulator is likely your culprit. There are two screws holding it into
your alternator. You don't even need to pull the alternator. Remove it
and you'll probably find the two brushes (two black square spring loaded
shafts) worn out. A good electrical shop can replace these, or a new regulator
is about $40. Install and, get a boost and happy motoring.
My advice...take the regulator out of the
alternator and take a good look. Better yet, just go ahead and replace
it if it has quite a few miles on it. Do it NOW, and you won't be sorry
[Testing Bosch voltage regulator on 7xx/9xx
cars: How can you tell if your voltage regulator has gone bad? I have heard
this is notorious for 700 series Bosch ones. What tests can you do? What
is the real purpose behind the regulator?] [Answer:] The real purpose behind
the regulator is to keep the battery voltage from getting too high. When
my regulator went bad, voltage would increase with engine speed, going
as high as 18-20 V. You can easily test the regulator function by using
a voltmeter to test your battery while the car is running. Look for voltage
between 13.8 and 14.6. If your voltage is higher than this, you probably
do have a bad regulator. The Bosch units (regulator/brush pack) is easy
to replace, usually even with the alternator in the car. If your battery
has been overcharging, it can boil off electrolyte and may need to be topped
Wiring is Failing. [Editor's Note: See the section on "Baked Wiring
Harnesses" in Electrical: Circuits, Relays for more information.] One quick
thing to check is the ground wire that goes from the alternator to the
engine block. That broke on me, resulting in my running off the battery
with the same symptoms you have. It was not until I pulled the alternator
that I saw the broken wire. Would have saved a lot of time to check that
first. I have been through this on so many cars that whenever it happens,
and the battery proves to hold a charge, I automatically yank the alternator
and head straight for the local rebuilder. I couldn't tell for sure at
first which alternator I had-turned out to be Bosch internal. I don't remember
how much to rebuild, but it was considerably under $100.
[Symptom: idiot lights all go on; also,
oil pressure gauge is erratic:] Having all the idiot lights go on at once
is not as strange as it might seem. This will happen if the small wire
leading to the back of the alternator is grounded. It will also happen
if the alternator is not generating any current. When this wire is at ground
potential, it is the same condition as before you start the car - hence
the idiot lights are on so you can check they are not burned out. The wires
for the alternator and also the o/p sender go around the front of the engine
under the main crank pulley. (If you get under the front you will see what
I mean.) Dripping crank seals often get oil all over these wires. Not to
mention it is hot by the alternator. Flaky insulation may be at work. If
you really want, you can reroute these wires around the right side of the
car instead and splice into the harness at the firewall.
Starter. [Bolts difficult to Remove:] Use a 2 foot extension bar with
a swivel socket or any other system of extensions, breaker bar, etc. to
get the bolt held firmly and have room to move the breaker bar, i.e. about
2 feet behind where the bolt actually is. [Note 2:] I used a long extension
for the lower bolt, and an ordinary 19mm ring spanner (the longer the better)
for the top bolt. It's tight, but otherwise no problems. [Tip from
Danny Halamish] On a 700/900 series, a long swan neck 19mm ring spanner
works wonders in removing or installing the starter. If not,
try socket -> u-joint -> 2x 10" extension bars (in this order).
Starter Fails: Wiring Fault. [Query:] I own a 1986 Volvo 740
Diesel. The mechanics have replaced the starter six times from March 1999
to July 1999. The starter itself is still under warranty, but each time
I have to pay the installation labor, besides the headache of being stranded,
towing, etc. I'm not a mechanic, but even I know that something is wrong,
wrong, wrong. Does anyone have any ideas? Even a list of possibilities
that I could have the mechanics check-out. [Response: Van Audekerce
Remi] I have seen this quite a few times and it was always a short in the
wiring harness that engages the starter when the engine is running. Most
likely the place were the wires have rotted is where the wiring harness
runs near the diesel pump. Cut the black sleeve open and check the wiring,
most likely the wire insulation will fall apart.
Will Not Engage. [Symptoms: I have an 89 740GL that sometimes starts
but sometimes does not. When I turn the key the car simply will not turn
over: no starter response on key to "start". However, all of the
panel lights, the battery level and starter assembly are good. When this
happens I usually put the car in Neutral and then back in Park which usually
works allowing the car to start.] [Response:] If your car is an automatic,
like my wagon, make sure that the transmission lockout switch located under
gear indication panel is not out of adjustment. A simple test is to push
the selector forward or back a little in the P position (the only one the
car should start in) as you turn the key. If the car starts, crawl under
and adjust the rod just a little and the problem should be solved once
and for all. Failing this option, check the switch and wires associated
with the lockout switch.
Start Problems and Battery Terminal Corrosion. [Query:] Car cranks
strongly but will not start. [Response 1: Jim Rothe] I've been
discounting -- actually, completely ignoring -- any
possibility of battery terminal corrosion,
mostly because I've always had strong cranking power. But in light of last
night's incident (and the prior one time occurrence) of starting with the
help of a jump start, I'm going to re-check these things. I'm reminded
of incidents with my RX-7 last year, when I was able to crank it strongly
and it wouldn't start. I replaced the battery a few weeks later when the
starter motor started sounding weak, and then my intermittent no-start
condition miraculously disappeared. I've since found out that early rotaries
tended to be a bit more susceptible to weak sparks (compounded by old,
low compression, engines) than other cars. Food for thought.
[Response 2: Eric Anderson] I may be covering something you have
already checked, i have not re-read all your posts but several things you
have written have rung some bells on micro-corrosion. I work for
Lockheed and spent years ( and some of our tax dollars ) chasing this buggaboo
down and around. MicroC exists everywhere and is aggravated by substantial
temperature changes. It is a microscopic or larger film of corrosion
that can build up on both positive and ground connections with a preference
to the ground connection, however auto's positive connection are just as
susceptible. Have you thoroughly cleaned the battery connections,
tightened and applied an anti-corrosive (exide cro-guard, etc)? removed
the starter B+ (positive cable) and brush the lug and the stud it attaches
to plus all washers and mounting points. retightend and apply antiC?
Same applies to ground connections.
[More Battery Cable Tips from Paul Grimshaw]
The battery grounding cable on Volvo 700-series cars fitted with the 2.3
litre engine is constructed of braided steel, crimped to lugs which secure
it in place. Over time, chassis and engine bay vibrations may weaken the
grounding wire. Furthermore, the effects of salt-induced corrosion can
adversely affect the crimped portion at the lugs--resulting in a poor electrical
contact. Any ground failure, whether total or partial, can play havoc with
electronic systems and can lead to the failure of the car's engine management
computer and/or mass airflow sensor Given the risk of failure
of this part, it's advisable to regularly inspect the ground cable and
replace it as a precaution every couple of years.
Battery Tips. [Tips from Rich:] Being involved in the telecommunications
power business since Mr. Bell was a pup, I have some knowledge about batteries.
If there were any additives that are useful in the long term they would
be commonly used. There are not. As to size, buy the biggest heaviest
battery that will fit. Typical car batteries are around 50 amp hours and
weigh around 45 pounds. Some parts chain may sell you a cheap, light battery
with a warranty, but they are counting on you not owning the battery when
it goes bad. Since batteries do not like to be used a small battery is
stressed more when cranking and when charging. Sure, a low charging rate
is best for a battery, but you have no control over that. At some speed
your alternator puts out 70-100 amps. Deducting 20 amps for fuel pumps
and ignition the rest is going into the battery.
Car batteries are designed for high-rate
discharge (cranking) and a reasonable life of 5 years. Other designs optimize
other types of service. Marine "Deep Cycle" batteries accept repeated full
discharge conditions. Telcom batteries are designed to sit there for 10-20
years with charging voltage applied and ready for the very infrequent discharge
when AC power fails. UPS batteries are similar but due to the competitive
consumer market they will not last very long.
Design considerations include a space
at the bottom of the case so that material that falls off the plates can
accumulate. Eventually it piles up enough to short out the plates. Longer
life batteries have more space but they also have less lead and therefore
less Amp-Hour capacity in a given size. The 20 year batteries have a lot
of extra space added for a long life seal where the post comes out of the
case. It is the nature of a battery to eat away the post seal. When it
does you get the white powder. Felt washers and grease do not keep
the acid from eating the seal away. The white stuff is the end result of
the seal failing and efforts to remove the white powder do not cure the
It is useful to remember that there is
no magic in batteries. Every manufacturer understands the chemistry perfectly.
The only difference is in the PR and advertisment depts.
The biggest battery you can fit has a
chance of having more space below the plates and a better seal. When Johnson
Controls made the Die Hard batteries they were good. Now that someone else
makes them they are not so good. Since Interstate distributes J. C. batteries
that is what I buy. You will not hurt the alternator with a bigger battery.
I always had good luck with OEM Volvo batteries but I understand that the
850s had a battery vith frequent failures. Sounds like the Purchasing Dept
saved the company a buck or two but gave the reliable cars a bad name.
This is not the first time that has happened, and will not be the last.
[BatteryTips from Tim Curry:] I talked
to Exide here in Tucson a while ago and found out a bunch about batteries.
Basically, here in the heat, they last an average of 28 months. If you
buy a "lifetime battery" for $100 and it lasts 3 years (heat is bad for
batteries) you spent $33.00 per year. Pro-rated? Oh yes, that saves you
(you pay some every three years). If you need cold cranking amps, the plates
are thinner and there are more of them to make more juice in a limited
container. They also heat faster under a load. Heat them once without enough
electrolyte (low on water) and you get the dreaded China Syndrome, cooked
plates. They distort, shed some of the lead and it settles to the bottom
of the container of the low cells. Get enough and the plates ground out
internally to each other if the level reaches the bottom of the plates.
Hot weather batteries? They use smaller plates and more electrolyte (it
acts as a coolant inside) to cover them so a low "water" condition isn't
as bad. Trade off is cold cranking amps (who needs it at 115 degrees, the
car is always warmed up). Best buy? A commercial battery (truck fleet
types) that you keep charged and full of electrolyte. 5 or 6 years at $65.
How long do most people keep their cars? $33 / year or $10 / year? Next
bet is a 4 or 5 year wonder from Wally's World for $29.95. It will last
for as many years as stated and you will buy another, so its cheap.
Oh yes, the battery, alternator and starter are a SYSTEM! Don't buy an
18 wheeler battery to start your VW or the alternator may be unhappy.
Don't buy a motorcycle battery to start your Volvo, the starter pulls too
many amps, the alternator will cook it from charging too fast and the starter
will poop out from not enough current to get the job done because of heat
$$$$$. Now you need one of each.
Connector Under Battery Tray?
[Query] Whilst cleaning up (minor) corrosion under the battery tray
on my '85 765T I found a rubber device (inserted into the tray) with a
cable which leads off to a (disconnected) 2-wire plug. Where does it go?
What does it do? [Response: Abe Crombie] It is a temperature
sensor that affects the voltage regulator activity. The idea was to alter
the voltage as battery temp changed. The voltage needed to charge battery
without overdoing it and risking electrolyte evaporation varies with the
temp of battery. This noble engineering feat was fraught with troubles
though as the sensor could (and most times did) get attacked by acid and
the temp value would be wrong. The result was exactly the thing the
sensor was there for, i.e., it would overcharge. There was a service bulletin
13 years ago saying to disconnect the sensor plug on back of alternator.
The voltage regulator would revert to internal temp regulation when the
sensor resistance went infinite.
Battery Dies: Causes. [Query:] My battery died at 40 months;
is this normal? [Response: Tim Curry] This could be a "normal" failure
of the battery, but check a few things first.
1) Battery cables. Positive side will be
more likely to have a build-up of crud or bad connection, but check both
cables. Is it clean at the connection? Is there corrosion at the cable/end
where it joins the clamp itself (grey stuff at the wire insulation or a
thickening/bulge of the cable somewhere in the insulation). Remove both
cables, clean the terminals (wire brush), use the red & green felt
rings under the cables to preserve the connection. Tighten both cables.
2) Get a multi-meter and measure the voltage
between the battery terminals with the engine off. If it is less than 12
volts, you have a battery or charging system problem. Use jumper cables
and get the car started. After you remove the jumper cables, check voltage
with the car running and no lights, AC, radio playing. Should be over 12.7
volts and 14 plus volts if the idle speed is raised a little. If this is
the case, your charging system is good, but your battery (or cable) is
3) If you don't show an quick increase
in voltage, check the fan-belt. If it is tight, check the voltage regulator
at the back of the alternator. It would be easier to work on it with the
alternator removed on some cars (turbo especially). There are 2 screws
that hold the regulator in place on the back side of the alternator. These
screws hold a brush assembly in place against the internal shaft of the
alternator, carbon blocks on a spring assembly attached to the holder.
The carbon brushes wear down with time and do not put enough pressure against
the armature to make good contact. Often the alternator is good, while
the brushes have worn out. The part costs less than $30 (US) and is available
from shops with a decent electrical parts supply.
4) It could be the battery. Here in Tucson,
the average life of a battery is 28 months (from the Exide corporation).
Our problem is not cold cranking ability, it's the heat. If the plates
inside the battery are exposed to heat, subjected to constant cranking,
or given a "quick charge" there is a lot of heat generated inside the battery.
The metal "grid" expands due to heat, the "paste" inside the grid is loosened
and begins to fall to the bottom of the battery or swells in place. This
will eventually cause a build-up of metal in the bottom of the cell which
can "short out" the cell.
A break in the grid or swelling, a loose
plate, an old battery, too much heat (or cold) and a dead battery is the
result. Don't buy a "lifetime" battery. It will cost $100 and still
fail before your life is over. Buy a moderately priced battery with 4 years
of life for $35-$40 and you will be spending $10/year, not $30/year. Plan
on setting your clock at 4 years and start saving for the next $40 battery.
Explosion; Wiring Chafing. Received panic call from wife that '88 740
Volvo just went completely dead on road and smoke was pouring out from
under hood. Claimed car was destroyed. PS: Only one child in back to add
to the situation. When I arrived, all electrolyte boiled out of battery
and battery cable insulation melted. Turns out was a direct short where
cables pass under engine. Volvo neatly bundles both cables in a plastic
sheath. Unfortunately too tight against bottom of engine and cut through.
Dealer was no help and said they never heard of such a thing. Same response
as to bad solder joint problem in my overdrive relay. A new battery and
cables cured the problem. Volvo later issued a recall for battery cable
[Technical Note from UK Volvo Club, 700
Section] On 700's the front suspension crossmember has the heavy
battery-to-starter cable running over its nearside front edge. These were
the subject of a recall some years ago as they chafed, leading to a big
electrical short (and under-bonnet fires in some cases). Apparently, most
cars were caught, but the odd unmodified one must still be about. The recall
modification involved fitting a sheathed clip, which lifted the lead away
from the cross-member. It's screwed to the nearside front cross-member
inside the fixing point of the lower suspension arm.
Drivability Problems; Rotting Battery Wiring Harness. Last weekend,
I uncovered the 1989 780T to show a friend. I haven't driven it in a while,
so I took him for a ride, so he could appreciate a well built Volvo w/
A/C that works. The car ran well, but seemed a little ''late''.
After glancing at the gauges, I noticed the volt meter reading low. I don't
trust the volt meters in Volvos, but felt the need to check alt. output
anyway. At the battery (new OE), the output (input, actually) was
12.9V. No good. I could hear the alternator charging, but checked the regulator/brushes
anyway. No problem. I checked the output at the alt. and the output was
14.1V Good. This car has a battery cable ''Harness''. After cutting
it open, I found the insulation to be gooey and loose. Current was flowing
between + and -- through the insulation. After replacing the harness, everything
came back to ''like new!'' The car's acceleration was impressive,
not just ''good''. The ECU said thanks, and the slight drop in fuel economy
went away. Reason # 14.2 to use a good battery. 12.9 just doesn't
cut it. The problem was wiring this time, but sometimes just changing the
battery returns life to a Volvo. Check your electrical system thoroughly.
Battery Discharge. [Query:] I am having an electrical problem
with my Volvo. About two months ago the battery went dead--slowly
over time. It was an old battery, so I though nothing of it and replaced
it. All was good for a month and a half, then it went dead again.
With the car running I measured 14volts across the terminals of the battery
(12 when stopped) and 14v off the main positive lead of the alternator.
What is the problem here?
[Battery Drain Diagnostics: Response:
Ross Gunn] To check to see if there is something draining the
battery while the key is off, remove the pos battery terminal, and with
an ammeter, measure to see if there is any current flowing from the battery
to the cable. If there is anything more than a couple of milliamps,
try removing fuses one at a time to see if you can identify the circuit
that is causing the drain. If this pins down a problem, a little
more sleuthing through the offending circuit should tell you what needs
to be done.
If there is no drain showing with the
above test, the charging system is suspect. Try measuring the voltage
at the alternator output terminal and battery pos terminal with all utilities
(headlights, rear window heater, fan etc.) on high. Any difference
in reading indicates a poor connection somewhere in the red cable from
the alternator. Don't assume that a crimp connection of a terminal
on the cable is good. Corrosion can introduce enough resistance to
prevent proper (any?) charging when there is a significant load on the
system (cold, dark, wet/snowy winter evenings). I have experienced
this on a 20 year old Brick.
[Battery Drain Diagnostics: Chris
Bowne] I agree with Ross Gunn that the best way to trouble shoot a discharging
battery is to find the source with the engine shut down and a multimeter
(set to measure DC current) in series with the positive battery terminal
lead. Other places to check besides the fuse block for drain paths
are the alternator and voltage regulator (if not internal to the alternator).
Disconnect/reconnect the connections on
them, one at a time, and monitor for drain. I had a problem on a Ford Taurus
once where the voltage regulator had shorted, and was the cause of the
drain. You may or may not find a source of a drain like this merely by
pulling fuses. In fact, you could end up with all the fuses pulled, and
still have the drain, like I did!
Someone on an earlier posting of this
thread mentioned checking to see if his alternator was providing output
by lifting the battery + terminal connection WITH THE ENGINE RUNNING. DO
NOT DO THIS! Many solid state regulators will be damaged/destroyed by this
condition. (And in turn may compound the causes of the battery drain you
Battery Drain Tips. [Tip from
JohnB] Check the specific gravity of the cells...if they're accessible.
With a fully charged battery, either from
your battery charger or the alternator, disconnect the battery and measure
the voltage, measure it again 12 hours later and it should be virtually
the same, maybe .1v less, no more.
Reconnect the battery to the car and turn
on the headlights on full bright for 10 minutes and every accessory in
the car...if the battery dies in 10 minutes replace the battery. Otherwise,
battery voltage should remain above 10.5 volts or so after this test. There
are load testers available in auto parts stores for about $30 or so that
will do a higher load test (couple hundred amps through a resistance load
bank) in about 10-30 seconds against a red/bad yellow/weak green/good voltage
If these tests still have you with a good
battery, then you just have to trace down the current drain, circuit by
FAQ for 7xx/9xx/90 Cars
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