Electrical Need help 3g alternator problem


New Member
Mar 21, 2019
Putnam, CT
Ok, so here is the dilemma. It is an 88 mustang rebuild built 302, custom dash with Marshall gauges with custom wiring, 3g alternator conversion with wire tuck, mud 6aln for ignition, fitech fule injection. All wiring for 3g alternator is correct except there is no dummy light or resistor inline with exciter wire going from gauge panel to voltage regulator built into the 3g alternator. No matter what I do the alternator is jumping all over the place when running with a normal load on it. When I turn off the 150amp DC breaker going from the alternator to the battery source the jumping and shaking stops because it is not sensing a load. I tried a new alternator and had this one tested at an alternator shop and the alternator is good. I posted a video of what it is doing on YouTube for anyone's viewing. Do I need that resistor on the exciter wire to stop this from happening? Please help it is driving me nuts.

View: https://youtu.be/jx34HNUs-v8
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Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
If that noise is coming from the alternator there's a problem. I've never heard a good alternator knock like that. Maybe I'm hearing a loose bracket or something else. Doesn't sound good.


Active Member
Jan 19, 2020
Sioux Falls, SD
Yes, you do need the resistor where the original one was. When I went to 3G with a Dakota Digital dash I connected the ends of the two wires that went across the charge light on the original cluster with a small resistor (I think a .25A 500 ohm) and heat shrunk the whole thing.
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