Battery Not charging

cracra · Post by **cracra** » 25 Aug 2018, 13:09

hello, and thank you in advance for your thoughts..

I have a 1991 940 Turbo Volvo and roughly 2 months ago, while I was driving it my lights, radio flicked off for a second, came right back on. However when I turned off car then it wouldn't start. Got a jump it finally started but barely got me hone cause battery was to low.. So I figured alternator, and replace it with a used one. Car ran fine for the next 2 days but then once again car died and battery was dead again. I thought it was the used alternator, so I bought brand new alternator. Again ran for few days and then it died again.

At that point I was lost and so I would put car on battery charger every night to get to work and back. Kept doing that until about 1 week ago battery would no longer stay charged. I then went and bought brand new battery. Seemed to have fixed the problem, however 2 days ago battery dead again.

I need to know exactly how many volts alternator should be putting out? Also, I have been thinking voltage regulator, but how likely is it that 3 voltage regulator would be bad? 1 from original alternator, 2nd from used one i bought, and 3rd from brand new one I bought?

Next could my instrument cluster have anything to do with it?
or my ideal ?

I am ready to throw my hands up. Please let me know your thought.

Post by **bmdubya1198** » 25 Aug 2018, 17:04

While running, you should have over 13 volts at the battery.

Next step would be to do a voltage drop test between the battery positive cable between the alternator and battery. Just use the DC volts setting on a multimeter just like you're checking battery voltage. It should be a low number, under a volt. Of course, also physically inspect the cable. If it's damaged in any way, that could certainly cause problems with your voltage.

If everything is fine at this point, you may have a parasitic drain on the battery. But check those things first.

Post by **jimmy57** » 25 Aug 2018, 18:30

1. does alt warning light come on before engine is started? it gets grounded via the skinny wire that plugs onto alternator. the current from the light circuit causes alternator to start charging. if that circuit is open then revving the engine past 3500 RPM should make it charge on that key cycle
2. the alternator has ground wire due to rubber mount bushings. With engine running and lights on there should be less than 0.3V between case of alternator and the bracket bolted to block. If not then that ground wire needs to be replaced/fixed.
3. could be a bad second alternator, that isn't impossible.

Post by **oragex** » 25 Aug 2018, 20:15

Already got good suggestions above. Basically, you have to buy a cheap multimeter and learn how to measure things. I'd also suggest getting one of these www.youtube.com/watch?v=IVDHzTkjHlc

Besides rotten cables/connections as mentioned above, you have to check for parasitic drain, alternator and battery. Note aside, your battery is mostly surely dead by now (by dead I mean it cannot take a charge any longer) so will need replaced but don't replace it until you find what the problem is

If you have tons of patience, this is a more detailed guide I made www.youtube.com/watch?v=0gc1SCGLfCk

Post by **RickHaleParker** » 26 Aug 2018, 01:23

It is a 27 year old car. Chances are the electrical system has not been maintained, hardly anybody does. Check the all wiring for the charging system for corroded/tarnished/damaged connections and/or wiring.

lummert · Post by **lummert** » 26 Aug 2018, 09:32

Could the crankshaft pulley be slipping?

cracra · Post by **cracra** » 26 Aug 2018, 14:46

If it was the crankshaft pulley would I hear it slipping? And is that the serpentine belt?

Post by **bmdubya1198** » 26 Aug 2018, 15:51

You would probably hear it squealing if it was loose. The only reason I could think that it would be slipping on the crank would be if the alternator is loose, or the belt is damaged (had that happen with a timing belt on my 740). Check for excessive give in the belt. It should be pretty tight.

cracra · Post by **cracra** » 27 Aug 2018, 00:06

thank you for the tip. So I checked and belt is tight and has no excessive give. But now I want to know if my instrument cluster has a fuse on the back of it? I read on hear some guy that had the exact same problem and the problem was in the instrument cluster...

Post by **jimmy57** » 27 Aug 2018, 08:54

do the warning lights all light when you turn on ignition before starting? Battery light is lit then too?