Gen 1 light comes on with rpm

[DieselStax]

last night on my drive home from work i noticed that my 86 m1008s gen 1 light came on. the truck has the origional 24v system and the driverside alternator is brand new and the front battery is brand new. gen 1 light is totally out at low rpm, barely glowing at half throttle, and the light is totally on at full throttle. if you have the heater on the light dosent come on as bright but it still comes on. hoping someone can help me out with my electrical gremlins. thanks

 

[cpf240]

My guess would be that either the belt is slipping, or the alternator is overcharging. Feel the pulley after it has been doing this for a while. Is it hotter than the GEN 2 pulley? Use a voltmeter to check the output of the alternator when it is loaded with the lights and heater blower going. Should measure around 14v or so.

Just because a part is new doesn't mean it is working properly.

 

[Warthog]

The heater blower and GEN1 exciter circuit are tied together.

Sounds like your voltage regulator or rectfier may be bad in GEN1.

Reading your other thread. What did you replace the GEN1 alternator with? A rebuilt stock unit, or a Civvy unit?

 

[DieselStax]

I got a cucv alternator fromrare electric off eBay and I don't think it's overcharging because the voltage gauge is in the high yellow range and my belt isn't slipping. If its the alternator that's bad I'll be mad, it doesn't even have 100 miles on it!

 

[DieselStax]

anyone with any other suggestions about how i should go about fixing this?