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'92 240 Charging Issue

LBM240Wagon

New member
Joined
Aug 5, 2017
Location
Central Florida
I just replaced the alternator on the 240, and it is not charging. Ground is good to the case, 12V measured at the B+ lug told me no charging. I checked the D+ exciter wire (connected to the alternator), and was reading 1.6V. I disconnected it, turned the car on and got 12V. Re-connected it to the lug and again 1.6V after startup. Disconnected it from the case, turned the car on and it measured 12V again. I then touched it to the lug and I believe the alternator turned on, and the reading stayed at 12V on the voltmeter.

Thinking the lug was possibly grounding to the case, I checked that and added a plastic washer for the hell of it. Still reads 1.6V when attached after startup.

Any ideas?



alt956.jpg
 
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Chain stores are sketchy on electrical stuff. Had issues with Vatozone alternators. Took it to a reputable rebuilder in my area, and he laughed at it. Gave me a rebuilt Bosch and sent me on my way.
 
Asking what the voltage is on your exciter wire disconnected, with the key on.

I think the guys ^^^ are on to something about bunk out of box alternators. We have had to do them three or four times before finding a good one with aftermarket junk.
 
why did you start down this rabbit hole?

where is the other end of the ground wire?


why did I start down what rabbit hole? The old alternator crapped out on me so I went to the parts store to get a new one....Is that what you're asking?

I have continuity from the ground wire attached to the alternator case to the ground at the battery.
 
why did I start down what rabbit hole? The old alternator crapped out on me so I went to the parts store to get a new one....Is that what you're asking?

I have continuity from the ground wire attached to the alternator case to the ground at th
yes, "crapped out"?
are both alternators acting the same?
you have a problem w 13.8v running or something else?
 
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You can also do voltage drop tests on the ground wire.
The crimps on the ground wires go bad underneath the insulation where you can't see it.


It's likely a bad reman alt.
 
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I do not have the old alternator anymore. In hindsight I should have had them bench test it 1st before swapping it out at the store. I took the new one back to the parts store and had it bench tested this AM. It failed... They are shipping in a reman Bosch alternator from Orlando. Hopefully I'll be back in business tomorrow. I will have them test that one on the bench before I leave the store.
 
I do not have the old alternator anymore. In hindsight I should have had them bench test it 1st before swapping it out at the store. I took the new one back to the parts store and had it bench tested this AM. It failed... They are shipping in a reman Bosch alternator from Orlando. Hopefully I'll be back in business tomorrow. I will have them test that one on the bench before I leave the store.

Everytime I get a parts store bought alternator I have them check it. I'm not sure what triple checked means from Autozone since I had failed ones out of the box before,lol.
 
I have had them where they charge ok, but let's say on a BMW, where the instrument cluster warning message will still be on.
 
I have had them where they charge ok, but let's say on a BMW, where the instrument cluster warning message will still be on.

This happens because the diode pack for the idiot light circuit is bad on a bosch alternator. There will be lower voltage output at the D+ than what is on B+. I bought a new volvo branded bosch alternator that did that and have seen it now a few times.

Over the last couple of years it really seems like it can be hit or miss with this stuff. I bought a reman Denso on ebay. The big bearing behind the pulley lasted about a year. It failed so badly that the internal fan started rubbing and making a horrid noise. I've also bought denso regulators that promise the 14.6v output and fail after a few months.
 
He swapped out my alternator for the Bosch unit this morning but I don't have confidence that is what my issue is/was. He tested it the same way he tested the previous one yesterday and it failed. He changed the connections on the bench (unplugged the little black box to the W+ (What is this box by the way?)) and it passed. He tested the previous alternator and it passed too.

So I brought the Bosch home and started checking my ground. I pulled the ground cable out and it looked ok, however when I bent it to straighten it out, the insulation cracked and broke apart. So I'm off to make a new one. I'm beginning to wonder if its something in the charge circuit? -I'm really regretting NOT testing my original alternator.
 
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