Truck not charging

[shakey]

Well just got done wasting my money and the morning on a rebuild kit for the alt from Geno's guess i still got to go buy a new alt

 

[DieselDoghouse]

Sorry to hear your plight…What's the status with the rest of thr truck? do you have tach, other gauges? If the crank sensor is out then the PCM will not 'instruct' (excite) the alternator to charge. If you know someone with some electrical test gear you can 'full field' (apply 12V) to the armateur (rotating winding) of the alternator. If your voltmeter takes off (don't do this too long) then the alternator and your rebuild are ok, something is keeping it from being instructed to charge. CSS failures are common in these trucks and are fairly easy to fix. Hope this info helps!!

 

[WilsonF]

I agree, don't buy an alt intil you know that's it. In my 96 the PCM controls the voltage on yours its call something else. In anycase you can wire around it by adding an external voltage reg. inexpensive to do and a good test to locate the problem. Do a search here or other forums for detailed instructions. After all that, do not get a rebuilt alt. have yours rebuilt at a local auto electrical shop. Mine needed new slip rings and diode pack, $90 at my local shop.


Floyd

 

[shakey]

Yes everything works fine thanks for the info i will check that out before i do anything. Does anyone know if there is an alt light to excite the field to charge or if the gauge serves that purpose . I can't say that i ever noticed a light but i never really paid attention.

 

[Steve St.Laurent]

Also make sure to check the alternator fuse in the underhood fuse box. I recently replaced an alternator and it was just that fuse that was blown. It's a 140a fuse if I remember right - one of the big square ones in there.

 

[BK]

Mine went out on me at the start of spring, barely putting out any voltage, an VERY hot to the touch compared to the block, telling me it had shorted windings... .

Out it went, in with the new, and it's fine... .

If it were as warm or cooler than the engine, I would then assume open diodes or bad brushes, meaning a rebuild would work... or and open fuse (but rare unless you've been abusing your electrical system - or corrosion) but it's not how all alternators fail.

Windings do short, and when they do, the alternator can get hot and have low or no output.