My alternator crapped out on me last week. I'm on my second carquest alternator since then. I'll start off by i already checked the wires on the valve cover. When I start my truck and let it idle for almost 10 minutes its giving me 11.8 volts as soon as i rev it just a little it jumps to 13.2 and the battery light comes on but very dim. if i unplug the alternator it goes to 13.6. is this a faulty remaned alternator or more something electrical??

 

At 11.8 volts your alternator is not giving you anything! It needs to be 14 volts at idle.

I'm not sure what your issue is though. Why are you on your 2nd alternator since then? What happened with the 1st replacement alternator?

 

I had the dim light issue a few months ago.I changed mine out.I keep a spare alternator in my shop.Both of the alternator(on the truck)and the spare have been rebuilt by a repitable alternator/starter shop.My readings are always 14-14.2 volts after the gpr goes off...I have read several posts about reman alternators going bad after a few months.Chris(F350-6) has had hell with several AZ alternators.He has my spare on now and has no problems.

 

Your just finding bad rebuilds from CarQuest. It can happen with a lot of brand store reman's I'm afraid. I've lucked out with a Checker's unit for a couple of years but...

 

ok - experience from 2 different 7.3l vehicles with permanent voltmeters and stock alternators

2000 f350 - gpr- original alt - 146000 miles- key on engine off - 10v on glow plugs on. Key on engine running glow plugs on - 11.8-12.2v. engine running glow plugs off below 1100 rpm - sometimes runs as low as 12.5-13v - jumps to 13.8-14.2 once 1100 rpm or above ( needs 1100 for full alt output)

2002 excursion - gpcm- new napa replacement "stock" - 135000 miles- key on engine off - 10v on glow plugs on. Key on engine running glow plugs on - 11.8-12.2v. engine running glow plugs off below 1100 rpm - sometimes runs as low as 113v - jumps to 13.6-14.0 once 1100 rpm or above ( needs 1100 for full alt output) - headlights on at night - 14.0 v - headlights on low beams plus fogs - 13.4-13.6v

The statement of 14v at idle - if its been running 10 minutes... probably yes but I lost an alt in the excursion(could see it right away but took several days to diagnose if it was the gpcm or the alt) and it took it several weeks to build the batts back up full voltage. should be at least 13v glow plugs off. Have you checked your GPR? sure its coming off? How long have you had it running when checking your voltages? This situation is why I run a volmeter in a 4 gauge a pillar set in both my 7.3's.

 

My alternator went out and I think it was due to a bad starter. The starter still worked, but looked origional and would turn over slow. I think it was drawing a huge load, it killed two batteries (replaced under warranty) and then shortly afterwards my alternator died.

They are expensive but I went with https://www.dcpowerinc.com/. I had read several threads on bad alternators through the chain stores. Soutthpaw installed this for me as I was out of town and we've had no electrical issues since. Wife said the Ex has been running great. I have two fuel pumps, a stereo, DVD, LCD screen, etc....