Dave M vin 03572
http://dm-eng.weebly.com/
If you put a diode in one direction, when you turn the key on, current will not flow through the bulb or get to the regulator as it should. If you put it in the other direction, when the key is off, a leak in the rectifier (or diode trio, if used) will not reach the bulb as it should. (Note the switch grounds the bulb's feed side when off on most vehicles.)
I agree a resistor will dim the bulb (and probably prevent the tell tail glow when the key is off).
I'm not sure, but I thought the DMCH alternators flashing was because the newer generation of regulators sent codes??
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I'm not surprised that 0.3 V turns the regulator on. You might find it interesting that, after a rotor has been used a while, the shaft can become a weak permanent magnet. Most of them are strong enough to get the alternator to kick in even if the field circuit (bulb's) is disconnected.
lol... Now I remember it was your's that sent codes.
Good idea!
But we're not sure the noise is coming from the alternator yet, are we??
I wanted to chase this down on the last D I mentioned before, but I had it doing head work and the owner said it never gave him a problem (and hasn't since).
What's been bugging me is that my battery charger would start the noise off. It would continue after removing it and I had to cycle the switch...
Directly to the field terminal, nothing feeding back to the chassis wiring.
Interestingly here's another member with the same issue just posted with a DMCH alternator. I get a 4amp draw associated with the regulator being active also.
http://dmctalk.org/showthread.php?18...w-with-key-off
My first thread on the alternator issue
http://dmctalk.org/showthread.php?17...t-ignition-off
Has a conversation with Stephen from DMCH this morning on this. We're going to troubleshoot with some information from my car....
Best
Ken
1981 DMC 12- Black
VIN 46**
Alameda CA
I was going to ask if the noise went away when you disconnect the field wire, but I gather it does from the link above.
With the field wire disconnected, does turning the key off send it to good ground or open.
A few drives had gone by without hearing it, but it did it again last night. It went away when I pulled the #4 fuse. On the schematic it looks like the shortest path between that fuse and the alternator is the white wire that connects to the cluster by the auxiliary relay (which also connects to the ignition). IIRC that relay was making a weird squealing noise last summer after the ignition accidentally got left on overnight when I had the car towed home due to the electrical failure. I have a spare one of those relays so I'm going to try changing it and see what happens.
Posts: 445
In addition to fuse 4, the auxiliary relay switches power to fuses 3 and 5. It also provides power to the coil via the ignition resistors. If it were failed completely, the car shouldn't run.
Just looking at this and considering that it went away with fuse 4, is it possible that the hazard switch is back-feeding a small amount of current to the aux relay contact then on to the alternator? The hazard switch is powered by fuse 6 which is always live. As a test, the next time it happens, pull fuse 6 (with fuse 4 still in) and see if it stops. If it does, that would implicate the hazard switch.
Ron