Electrical: Engine Starting, Charging                                                          FAQ Home
 Volvo Maintenance FAQ for 7xx/9xx/90 Cars                                                                                                                     Version 5.0
Starter and Solenoid Problems

Alternator Getting Weak

Checking Alternator Diodes

Testing Alternator/Battery Voltage

No Juice from Alternator: Not Charging?

Alternator Wiring is Failing

Removing Starter

Diesel Starter Fails: Wiring Fault

Starter Will Not Engage

Hot Start Problems and Battery Terminal Corrosion

Car Battery Tips

Car Battery Dies: Causes

Battery Explosion; Wiring Chafing

Unexplained Drivability Problems; Rotting Battery Wiring Harness

Slow Battery Discharge

Starter 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). 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.

Alternator 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.

Checking Alternator Diodes.  [Tip from Corey Glassman, “Electrical, Charging and Starting System Tips and Techniques”,  Underhood Service, Sept 1999]

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 Diodes
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.

Testing 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 engine running!

No 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? Corrosion?
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 later!

[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 off.

Alternator 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.

Removing 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).

Diesel 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.

Starter 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.

Hot 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.

Car 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 problem.
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.

Car 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 bad.

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.

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 chafing.
[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.

Unexplained 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. 

Slow 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 are troubleshooting!)

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 scale.
If these tests still have you with a good battery, then you just have to trace down the current drain, circuit by circuit.

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