m42 cluster/ alternator issue.

[kansas-ix]

I need your guys help badly. Ok so here is the story car has been not starting the best for a few weeks thought it was the alternator belt as it was a little loose, so put a new one on. Then yesterday starting giving me troubles so put a new battery in that got me about 250miles, then this morning wouldnt start jumped it went to Oreilly's they say alternator not giving out enough juice put in new alternator, and jumped on highway got 30miles and then starting acting like alternator is going out, so turnaround and went back home, didnt make it. Died. Talked to Uli at Hafkemeyer in KC very reliable man said if i turn the key and the battery light on the dash doesnt light up then, this will prevent the alternator from working- he said replace bulb and should be good, so i did, still doesnt light up so, then he said that the cluster wiring must be bad, so got new cluster, still same problem.

ANY IDEAS please!!

[Farbin Kaiber]

Trunklight.

[AndrewBird]

I'd guess a bad ground on the alternator.

[TwoJ's]

Okay, first of all, have you even put a multi meter on the battery while the car is running to see how the alternator is doing? Have you charged the battery, or did you just throw it in the car and go? What is the voltage across the battery when the car is off? Pull the (-) battery cable (ground strap) and measure current between the post and the ground strap. How many mA? You need to provide more detailed information about what you've done before we can make a decent educated guess.

Second of all, don't make a thread linking to another thread you've started.

[e30Matt]

Yeah, probe the battery with the car idling and a few accessories turned on (headlights, etc.) to put a little load on the system... main thing to look for here is voltage, you want somewhere north of 13 (14-14.5 ideally) but south of about 15.5. Let us know after that.

[kansas-ix]

voltage was 11.72 when oreilly checked it.

[WillisE30]

Multimeters are worthless for testing charging systems. Voltage is an ok indicator but if the alternator isn't putting out current it's game over. It's entirely possible you got a bad alternator from the parts store. As someone else already mentioned check your grounds on the engine, alternator grounds through the block.

[TwoJ's]

They're not worthless, just not all-telling. Generally if the alternator is providng enough voltage, then the windings are working properly and current is sufficient as well.

Just out of curiousity, what kind of amperage do our alternators put out?

[Toms73NovaSS]

voltage was 11.72 when oreilly checked it.

Too low IMHO. Should be 13.3 +

[TwoJ's]

Too low IMHO. Should be 13.3 +

That depends on if that was while the car was running, or right when he bought it, or if he charged the battery before he stuck it in there.

Kansas: You know the alternator is not a good way to charge the battery, right? It will keep it charged, but you should do a slow 2A charge and then meter it to see if it's at at least 12.5v.

[TwoJ's]

Multimeters are worthless for testing charging systems. Voltage is an ok indicator but if the alternator isn't putting out current it's game over. It's entirely possible you got a bad alternator from the parts store. As someone else already mentioned check your grounds on the engine, alternator grounds through the block.

And pretty much every multimeter I've had has an ammeter in it. I don't know what the amperage tolerance is on the cheap ones, but how else would you test for current?

[WillisE30]

And pretty much every multimeter I've had has an ammeter in it. I don't know what the amperage tolerance is on the cheap ones, but how else would you test for current?

A vat 40 or Vat 60 or other device capable of handling/applying a load. Multimeters generally have a max of 10-15 amps. Alternators put out anywhere from 70-120amps depending on the application...
As for voltage I've seen plenty put out good voltage and insufficient amps.

[mikeedler]

make a homemade ground cable from the housing of the alt. to the car body. alll your problems will be solved.

[kansas-ix]

thanks for all the input.

[e30Matt]

Do you have an Advance Auto nearby? We've got a tester that's designed to load test alternators on the car, take it by one if you can.