Location: Northwest Florida
Posts: 324
My VIN: Midproduction
Looks like the feed through the #191 bulb in the panel results in a 3 volt signal to the +L line on the alternator. Playing around with a potentiometer I was able to pull the alternator regulator online with a 0.4 volt signal- that's a low as I could go with the pot I had on hand (turned all the way down with a 1.5AA battery as the supply). It might come on with less that that. Seems like the alternator might be a little sensitive to something like a bad ground holding the voltage up on that feed line...
1981 DMC 12- Black
VIN 46**
Alameda CA
Location: Northern Michigan
Posts: 1,147
My VIN: 1880
Club(s): (DCO) (DCUK)
I had this EXACT problem with my DMCH alternator this fall! I went out to the garage and could hear a high pitched whining coming from the engine bay. I tried a lot of troubleshooting, but the whining noise seemed to go away on its own, but I’m not confident it’s gone for good.
Patrick C.
VIN 1880
For what it's worth when my DMCH alternator quit a few weeks ago it had a whine to it but it still charged at higher rpm. Low rpm was nothing. (I don't recall hearing any noise when the engine was off however).
I doubt I will never buy another alternator as long as these local guys rebuild it like they did this one. Almost 15v on the gauge at idle and in almost 11 years and 3 alternators I have never had the confidence to run the AC at night because with lights and ac fans, I would go into single digits.
My advice (which I followed from another member) is have yours rebuilt by a reputable place. Try to find a rebuilder that uses American components and has been in business for some time.
My rebuild cost $90.00 and it came back cleaned looking brand new and with a new pigtail.
Last edited by Michael; 12-27-2019 at 10:30 AM.
Dave M vin 03572
http://dm-eng.weebly.com/
All,
Issued resolved- seems like a problem with the new alternator. DMCH replacement was sent and installed; all is good. Great service from DMCH! No more whining from the alternator with the ignition off.
Best,
Ken
1981 DMC 12- Black
VIN 46**
Alameda CA
Posts: 743
Location: Northern Michigan
Posts: 1,147
My VIN: 1880
Club(s): (DCO) (DCUK)
I wonder if this is a known flaw with the DMCH alternator. If mine is still doing this in the spring when I pull it out of storage, I’ll have to contact them for a replacement.
Patrick C.
VIN 1880