Hi all. Having a problem with my '92 240. Drove to work, 30 miles on a rainy day. Had to run rear defogger, headlights, wipers and had a charger plugged into my lighter. MAde it OK. When I got in to go home, it ha a sluggish start. Got about 15 miles and going up a hill, started having a bad miss. Pulled off and turned it off. then tried to restart, and almost completely dead battery. Charged battery overnight, went back and drove it the last ten miles home. Checked the battery after I turned it off and reads 12.6 . Started it up and pulled the negative cable off and it started acting like it had a miss. Put the negative cable back on and it smoothed out.

I did change the belts a couple of weeks ago. The belts are tight and everything is running fine, is it possible overtightening belts could cause this? I have about a half inch latteral play in the belts. Or Is this most likely an alternator that is charging but not at peak efficiency, IE getting ready to go out or possibly another culprit. Any suggestions would be greatly appreciated.

 

You are most likely having a charger EXCITER issue. Make sure the warning light for the charging system is ON when key is in position II, and it goes OUT once the engine starts. Many Volvo owners chase that problem and change alternators unnecessarily. IF you do need an alternator just change the brushes (regulator) as very little else ever goes wrong with an alternator.

 

running the car wtih the battery disconnected is bad, too. the battery acts as a stabilizer and load for the alternator, without it in the circuit, the voltage can bounce all over the place.

if the battery is fully charged, it will read about 12.6V or 12.7 after its rested a few hours. when you start the car, it should read 13.9 or so, about 1.3 volts higher, if the alternator is working and charging properly.

what lev said, IF the alternator isn't working, replace the brush/regulator assembly, its about $40 from IPDusa or FCPeuro ... this can be done without removing the alternator from the car.

 

Great info, thanks. So if the charger exciter/warning light is acting as it should, then my next step is to check voltage with teh engine running. would it be wise to turn on some items in teh car to check the electrical draw, blower fan, headlights and such and see if this affects my output?

 

I generally first test the charging voltage with engine running but everything turned off. as you add loads like the headlights it might take a little more RPM than an idle to reach full charging voltage, this can be seen in the headlights being a touch yellow at idle, but brightening slightly as you rev the engine up to, say, 1500 or 2000rpm. its fairly normal if thats how it behaves. as long as the charging voltage is higher than the battery rest voltage, then its putting power into the battery instead of draining it.

if the dashboard charging indicator light is working properly, the alternator is probably working. worn alternator brushes will usually cause that light to flicker dim when the car is running, or light solid, perhaps intermittently.

 

I checked the alternator warning light. In accessory position II it comes on. After I start the engine it goes off. I checked the voltage at the battery while the engine was running and it was reading about 12.6V. I did turn on the blower, and headlights and it dropped to about 12.1V. The warning light in the instrument cluster did not come on while the engine was running. I will interject one thin though, Not sure if this makes a dfference. All of the warning lights that come on in accessory II sometimes stay when the engine first cranks over until I give it a little gas, then they all go out.

So pretty much the battery reads the same 12.6 volts wether it's running or not.

 

k, i'd get a new brush-regulator assembly and install that. $40 from the source I liinked above. disconnect the battery negative terminal before doing anyhting, disconnect the wires from the old regulator, unscrew it pop it out, put in the new one, screw it down, replace the wires (do note which wire goes where...)

 

Thanks again for all the help. Is this procedure easiest done from the top side or underneath the car?

 

my daughter has the 240 and she's never home, so I can't go look. on my 92 745 turbo wagon, the alternator is topside on the left intake side of the engine, so very easy to access from the top, Id likely just remove some of the intake air plumbing to make it easy.

I think on our 87 240, the alternator is on the other side of the engine, fairly low so I don't know if the exhaust manifold is in the way or not. I know Volvo moved it around a few times during the production cycle of the car.

the alternator has 3 total connections.

1) D- is a big heavy black wire to ground
2) B+ is a big heavy red wire to the starter solenoid and the battery
3) D+ is a thin red wire that goes to the alternator light in the dashboard, and provides the bootstrap power via the ignition key from the battery so the alternator can start.

and ya know, its been so long since I did this, I don't remember if the wires even have to be disconnected on the Volvo ones... in fact the only alternator I've repaired was on a VW Jetta.

here's instructions on a BMW one... http://tis.spaghetticoder.org/s/view.pl?2/04/70

you can also just replace the brushes themselves, much cheaper but more work. http://tis.spaghetticoder.org/s/view.pl?2/07/60

I believe FCPEuro has the brushes for sale.

 

OK, I finally got my part. I ordered the OEM Bosch voltage regulator, The same on that was in it. I took the old regulator out, Mine did not have any wires attached to teh regulator, just 2 screws holding it in. The old brushes were indeed very worn. I put teh new one in and it still reads about 12.5 when running. Is it possible to put the voltage regulator in and not do it correctly, IE the brushes aren't where they are supposed to be? I see that they are spring loaded, could I have put it in wrong and the brushes are not engaging, or is it a situation where if I can get the screws in It's probably right. LOL

 

pull it out again, and see if you can get a good look in there with an inspection mirror and bright light at the copper rings that the brushes engage against. if they are deeply worn, then you may need a new (rebuilt) alternator. its probably filthy in there with carbon dust

here's one (out of a porsche) partially disassembled...


and a diagram of the key parts...