Engine/Transmission (1994 - 1998) Alternator Thermal Shutdown?

[Woodenhead]

Do our alternators have some sort of thermal shutdown to keep from cooking them.



I'll try to keep this short. I killed the batteries in my truck by leaving my 2low lockout solenoid on for a few weeks without driving the truck. Anyway I jumped it, got it going and made a couple shutdowns/starts after only running it for about 15 mins (I know, shoulda left it running). Once I finally hit the road my "GEN" light came on about 5 miles down the road and the voltage was down around 12 instead of the usual 13-14. I checked all my fuses (mainly the 120A alt. fuse) and all was well. I put my hand on the alternator and darn near burned myself. So thinking I smoked my 3 year old alternator I went home, grabbed a different rig and went to town.



Once I got home I started the truck and the GEN light stayed off so I set the idle at 1000RPM for about 20 mins to finish charging the batteries. The voltage came up to 14 and the light stayed out.



My guess is the alt. has a thermal safety and if I would have let the truck idle and charge the batteries at say 30-40 Amps the alt. would have been OK and stayed cool enough to get the job done. Since I started driving and it was probably cranking near full load (100-120 Amps) it probably got smoking hot and shut down.



Or maybe I'm on the thin edge of a fried alt. and it'll pack it in real soon.

I know it's best to use an external charger to charge your batteries when you kill them this hard but I had to get rolling.



So much for keeping it short.



Thanks,

Mike

 

[Hitec.Redneck]

Do our alternators have some sort of thermal shutdown to keep from cooking them.



I'll try to keep this short. I killed the batteries in my truck by leaving my 2low lockout solenoid on for a few weeks without driving the truck. Anyway I jumped it, got it going and made a couple shutdowns/starts after only running it for about 15 mins (I know, shoulda left it running). Once I finally hit the road my "GEN" light came on about 5 miles down the road and the voltage was down around 12 instead of the usual 13-14. I checked all my fuses (mainly the 120A alt. fuse) and all was well. I put my hand on the alternator and darn near burned myself. So thinking I smoked my 3 year old alternator I went home, grabbed a different rig and went to town.



Once I got home I started the truck and the GEN light stayed off so I set the idle at 1000RPM for about 20 mins to finish charging the batteries. The voltage came up to 14 and the light stayed out.



My guess is the alt. has a thermal safety and if I would have let the truck idle and charge the batteries at say 30-40 Amps the alt. would have been OK and stayed cool enough to get the job done. Since I started driving and it was probably cranking near full load (100-120 Amps) it probably got smoking hot and shut down.



Or maybe I'm on the thin edge of a fried alt. and it'll pack it in real soon.

I know it's best to use an external charger to charge your batteries when you kill them this hard but I had to get rolling.



So much for keeping it short.



Thanks,

Mike

I had a simular problem with my 2002. I had a battery short and the alternator just stopped charging. The light Gen light came on, so I headed back home. I shut the truck down and restarted it, all was well. I bought 2 new batteries and have not had any problems. I think there is some circuitry that causes the alternator to stop charging when the load it too great.

 

[Woodenhead]

Thanks for the Reply Redneck,



I've put a couple hundred miles on and all seems to be fine. Looks like I got lucky this time.



Mike