Hi, I have searched but can't seem to find anything definitive that relates. My brother has a 94 and he dropped battery cable and shorted it out under hood. (not sure why truck was running) Anyway of course it is now not charging. He has had alt tested and appears to be OK. He has bypassed the ECU with a regulator no difference. He has supposedly checked the Fusible link and its OK, I have been doing some reading and every once in awhile someone refers to crank sensor, what does this have to do with a non charge situation?  He is going to bring truck to me so I thought I would pose for suggestions.  I cant validate the alt test at all so I will check diodes to see where the fall into the picture. I of course will look for proper wiring from the regulator and for smoked wires and all the obvious stuff. Not sure about this crank sensor tho, anyone explain that one? 

As far as I understand as long as the ECM sees the crank/cam sensor signal while the truck is running is allows the alternator to charge. If that sensor is not sending a signal to the ECM that the engine is turning, the ECM doesnt allow the alternator to charge. If the alternator did in fact test good, I would be afraid there are problems with the ECM. You should plug in a scanner and see if there are any codes in the computer. If there are, it may lead you to wherever the problem is.

Just a small correction. The tach signal is sent over the CCD Network to the PCM which controls the alternator. So if the PCM doesn't see the tach signal from the ECM then it will not apply grounding to the field on the alternator. 

 

Thanks for that. Cant ever keep these things straight!

Thanks, I will now be able to confidently tear my bro's truck apart!

I have a question on a charging issue. My son borrowed  my truck to pull his  28 ft. trailer to go elk hunting, he got it stuck 12 inches of snow up on the Mogollon rim and had to use my winch to get out. my winch is powered by my passenger side battery and is protected by 50 amp. breaker. With the engine running he engaged the  winch and the voltage gauge in the dash dropped to 8 volts  My scan2 gauge was showing between 13.2 and 14 volts while this as going on. The abs light and CEL came on and stayed on even after the winch was disconnected . The winch worked normal so I don't believe there is a problem with it.

 After driving 10 miles every thing but the abs light cleared. Yesterday after a couple of miles all the warning lights were cleared. He is still up there so I haven't had a chance to check for codes. Does this sound like a bad ground issue? I've used this winch before and never had a issue .

Possibly motor noise from the winch tripped the lights.

Thanks Mike

I just found out they were hooked on to another vehicle , Could that have caused a polarity issue?

Polarity issues would have caused a huge explosion of sparks. As for the winch motor if it hooked up backwards it just runs backward so reel in is now reel out and visa vera.