Need some help with the charging system on my truck, yesterday check gauges light came on five miles from the house voltage went to zero only gauge showing a change, took alternator in to be tested this morn it had two failures (not sure which) replaced with reman run truck and check gauges light comes back on continued running got home cut
It off no restart- any ideas

 

the PCM (truck computer) turns on the alternator, no built in voltage regulator.
i have heard of a alternator you can buy that is a direct fit with a regulator built in if your PCM stops turning on the alt.

mine is getting lazy on the 99, it take 13 seconds for the voltage to start climbing, with the grid heater on in this cold weather the check gauges come on most every time until the alternator starts charging.

 

Yea I was kind of leaning towards PCM problem, how is that fixed or is the only option the built in regulator alternator

 

either one, the alt would be cheaper, new PCM the right way if in fact that is the problem.

check all the wires from one end to the other first.

 

before condeming alternator or ecm, make sure the grid relays have not stuck on causing a massive electrical load, easy to check with a test light, if the grids are stuck on both sides of the relay (large posts) will have a positive signal and will light up your test light, also grids will be hot to the touch.

 

your going to have to poke around with a volt meter first. check the voltage before starting, start it up and check, check voltage at both batteries, check the voltage at the big post on the alt, they all should be the same. if not there's your clue.

there is a big fuse in the box under the hood for the alt, with out looking, it is the first on in the box with bigger wires hooked to it, check voltage on both sides.

good point on the grid heater, I'd unplug it for the voltage test.

 

Checked the main fuse block and the main 140 amp fuse was shot replaced and is now charging and no more check engine light, thanks for the help now I'm ready for some slight mods starting with exhaust just can't decide if I'm just goin to go straight or get a system