Hey everyone,
I'm having some issues with my '92 240 sedan and could use some input. Several weeks ago, the warning lights on the dash all came on, and stayed on whenever the car was running. I researched and diagnosed this as an old/bad voltage regulator.
Fast forward a week or two later- while driving my stereo suddenly shut off, warning lights were flickering, and car was idling rough, sort of a back and forth rhythmic idle that got progressively slower until the car died. Battery was dead- got a jump and drove home assuming the voltage regulator was totally fried. At that point I could jump the car but it would die the same way again within several minutes.
I replaced the voltage regulator yesterday (old brushes were indeed very worn) and reinstalled the alternator. But with the new regulator, the problem persists. Battery takes a good few minutes to charge, then once I jump the car it idles for a couple minutes before dying. Note that the battery is new as of a month ago. Any ideas? I'm thinking I should get the alternator tested. If the alternator is ok, could it then be a wiring/connection issue? Any thoughts are greatly appreciated.

 

Yep its your alternator!!
voltage regulator will take voltage up above normal levels.

Goldenblock 2 million miles and still running!!!

 

Test the alternator to make sure, easy to do with multimeter. Should be putting out 13.8+ volts when running at idle--it's probably not...

 

Got the alternator tested and it's totally fried. Now I'm wondering what to replace it with. The rebuilt bosch alternators I see online don't come with a pulley- the only one I can find that does is a Denso, but I worry it won't fit since the original is a Bosch. Could I remove the pulley from the old alternator and put it on a new (rebuilt) one? I can't find a socket big enough to remove it. Any ideas ? Thank you

 

Yes, that's what you do - transfer the old pulley and fan on some cars, and whatever spacers/washers are needed!

 

also get new rubber alternator mounts, they loosen up with age and harden, then the alternator doesn't sit square and causes excess belt wear and noise and stress on the alternator bearings.

IPDusa used to have blue poly ones that lasted longer than the originals but I couldn't find them last time I looked. local volvo specialty shop was using those on every job where they touched the alternator.

 

I’ve encountered a new issue and could use some advice..

I finally got around to installing in a new (rebuilt) alternator. I made a huge mistake by initially lowering the alternator into the engine compartment with the battery still connected. I don’t know exactly what touched what, but I do know that part of the new alternator touched metal and briefly created sparks and smoke, several times. I quickly removed it and disconnected the battery. I then installed the alternator. Now I am unable to get the battery to charge. It was totally drained to begin with, but I can’t even get it charged enough to turn on the dash lights. I’m worried I blew out some sort of fuse, or worse, killed my recently bought battery and new alternator. Any thoughts or theories greatly appreciated..

 

once a battery is totally discharged (like, less than 9V at rest), most 'smart' chargers won't even try to charge it, unless they have some sort of 'override' mode. I typically find that if a lead acid battery was discharged to below 9-10 volts at rest at 68F, then even if you recharge it nearly immediately, it has less than half its original capacity left, the battery is pretty much shot.

now, if it was totally discharged in the first place, I'm not sure how you got much in the way of sparks, but if it was at like 7 or 9 volts (beyond 100% discharged, but still holding some residual juice), its possible your short circuit blew an internal battery connection. *ALWAYS* disconnect the NEGATIVE terminal at the battery before working on ANY electric circuits.

re fuses, there's no fuses in the starter/alternator circuit. big fat red wire from battery + terminal goes to the starter, then a somewhat less fat red wire goes from the starter to B+ on the alternator, there's no fuses at all in this circuit, because the starter can draw 100s of amps, and the alternator can output up to 90 or 100 amps. the other wires involved (circuit 50 'start' control to the starter solenoid, and D+ to the alternator) are both switched by the ignition switch, so as long as that was 'off', they are disconnected.

 

Appreciate the reply. My electrical knowledge is pretty limited so thank you. I may have misspoke by saying the battery was “drained,” but I charged it off another car for 15 mins and was hardly getting anything. I bought a charger today- the battery is now hooked up and reading 12.9V with quite a ways to go. The alternator came with a warning to only hook it up to a fully charged or new battery. Hopefully what you said is not the case and the battery retained its full capacity. I guess I will know in the morning. Thanks again.

 

if you are getting 12.9V reading on your battery, that indicates fully charged. Anything above 12.7V is pretty much 100%. So if the car is still running into problems, you know it is NOT your battery being drained.

 

if its reading 12.9 when the charger is running, its still deeply discharged. probably equivalent to around 11.7-11.8V at rest, basically nearly 0%. the voltage will be up around 13.8V when its 80% charged, then a good 3-stage charger will hold it at 14.2-14.4V for the 'absorption phase' for the last 2-4 hours to fully charge.

to get an actual charge state reading, you need to let the battery 'rest' with no charging and no load for a few hours, THEN take a reading.... at 68F 12.6V is 100% charged, 12.1V is 50% charged which is as low as you should ever let it go. at lower temps, the voltages will be lower, you can find tables for charge state vs voltage vs temperature. a sealed 'maintenance free' battery might be 0.1 or 0.2V higher at the same temp and charge state. ditto AGM batteries.

 

Thanks all for your help. The battery charged up nice overnight and the car is running smoothly again with the new alternator.

 

if you wing by a battery store, and have them do a load test on that battery, it probably has half or so of its original CCA capacity.

 

Good to know. Would it be problematic if that is the case?

 

well, a low CCA battery will have trouble starting the car in cold weather.