I just started having this strange electrical issue. This morning I started the truck and waited for the GPM to turn off. I can tell by the dash lights going bright. Didnt seem to happen so I just left for work after a few minutes. On the way I notice that when I hit the gas the dash lights dim.... let off they go bright. I turn off the fog lights, no change. (just put LED bulbs in them) Vacuum pump not running, turn heat to off, turn radio off....nothing, same issue. I get to work, open hood and the power seems to be fluctuating. After about 2 minutes, it seems to stop. I'll give it all a check when I get home but Im stuck at work until after 5 today.

History: last winter I put a Quickstart 140 amp alt on it, about 3 months ago new batteries. No issue on the batteries just time. Last couple of weeks air bags (no electrical) and a new steering box, again, no electrical. Couple of days ago the LED fog lamp bulbs.

Im thinking one of two things, something with the alternator or the GPM (FICM?) freaking out?

Any help would be appreciated. I have a towing job in the morning and dont need to be stranded. Thanks in advance.

 

You have to start at your alternator, battery, and chassis ground connections, and work out from there.

If you think an individual component is the cause of the problem, start pulling fuses to see if there is any change.

 

I tested the batteries before start up, 12.5 amps each. Checked extensively for faulty connections and frayed or cut wires, all is good. Once it starts, things remain at 12.5....the first time for a few minutes the second time about 1 minute. I had the tester at the alternator (second start), 12.5 and then it seemed to suddenly start charging, up to 15 it goes and stays there until my back got sore.

Shouldnt the alt charge the whole time? Is there something in the system, maybe the GPM cycle, that turns off the alt until its done? Not sure what this could be.

Also, if this cycle of turning off the alternator happens while driving, is something going wrong with the GPM?

I removed my intake air heater but the relay that it was powered from remains. Should I have removed it?

Ugh, just when you think things are golden, stuff happens.

 

I know zip about oil burners, but that sounds like a bad alternator or possibly a bad connection in the charging circuit. It should immediately start charging when the engine is running.

 

So based on your posts, have you watched output and had someone step on the gas while you watched?

 

Yup, fairly sure the alternator is not working. Drove it home on batteries today. Ugh.