I'm looking for a little advice with my charging problem my truck seems to be having. First off, I recently replaced both batteries and the cables at the batteries are tight and clean. I have removed, sanded, and replaced with dielectric grease all ground cables and checked all positive cables. What my truck is doing is, after the notorious voltage drop at first startup due to the heater grids cycling the voltmeter in the dash will not show anymore than 12 volts(verified with a dvm at the batteries) until I throttle up the truck to at least 1200-1400 rpm. Then it will rise to about 13.5 volts, but then as i return it back to idle it will slowly return to below 12 volts and the check gauges light will come on. I've checked to make sure the grid heaters weren't stuck on, what else could it be? My truck has 83k on it. Thanks.

 

read (alternator quit) by litefoot

 

Ok litefoot, I read your thread and I'm taking the alternator to have it checked tomorrow. The pos. cable was tight and not corroded. The 2 wires for the field terminals are in one connector and they looked good and had dielectric grease on them. I checked the continuity of the field wires to the PCM and I had .4 ohms on the dk gn wire to b10 on the PCM, but on the dk blue wire I could not get any continuity. My Hanes manual shows the wire going to c12 on the PCM, but splices in with the ASD relay. Does anyone know if this is right, or where the ASD relay is? Thanks.

 

Well, just had the alternator tested and they said it was fried. I ordered a new one from ebay and will replace when it comes in. Thanks.

 

When you install it make sure the alt. and mount are clean and tight, I chased the problem of TC dropping out of lock up for six months before I found the cure. Each case seems unique to the problem. I've got a new one today, air bag light comes on intermittently?
good luck.

 

UPDATE. Well, after learning the diodes were fried in my alternator, I ordered a whole new alternator from ebay for $99 and threw the old one on the bench to rebuild later. Installed the new one and all my charging probs are gone!! I guess I didn't realize that bad diodes would cause a "weak" alternator, but at least it's fixed. Thanks for the help.

 

Very good news!