Hey, I know it’s been a while but I got tied up with some other projects. I returned to this problem again today and now have more questions than before, I am now able to confirm that I am getting 12 volts to the alternator I did some re wiring so now I know it’s getting 12 volts. I fired the truck up to see if it was charging and it wasn’t so I hoped in the truck and made it high idle just for the hell of it, I noticed it was kind of making a strange humming noise then all of a sudden the noise went away and a puff of smoke came out the hood. I imidiatly shut the truck off and opened the hood but nothing was burning, it smelt like burning rubber. I still don’t know where the smoke came from. I thought maybe one of the belts broke or burnt up but they both looked good to me. Although the one v-belt that goes to the alt was kind of sitting crooked. So I carefully fired the truck up and sure enough there was no smoke and the battery was charging. I let the truck run for a while to make sure it was going to stay charging but about 2 minutes later I checked it and the voltage was at 12.9 and steadily dropping. I shut it off and just stood there pondering what to do and in doing so I accidentally touched the fins of the alt and they were extremely hot. Anyone have any ideas of what is going on here?

 

After looking at it more the burning rubber smell and smoke was definitely from the alt belt but I still don’t know why is started charging then stopped

 

An alternator will cook itself if allowed to charge a dead battery
If you have one that is real dead, you need to charge it some with a battery charger before letting the alternator take over
A bad connection will do the same thing, sounds like you have that sorted out
Take the alternator to a parts store to be tested
A worn out brush set will also do the same thing

 

Ok, I know the battery is good and fully charged, and all the connections should be good, I hope it’s not the alt because it’s brand new

 

That doesn’t mean anything.

 

Ya I know that’s why I said I hope, I will still have it tested

 

*Any short to ground or a shorted component that is hooked up to that wire
I have an 88 EVTM and I can post the charging circuit
Rather see you procure an 87 one to be damn sure of the wiring
The EVTMs provide splice and ground locations along with a bunch of other good info

 

thank you, but I already did fix that problem I just re-wired it

 

Well, if the alternator tests good and you have 3 volts on the excite wire, you have a problem
That schematic rla2005 posted looks correct to me
Jump 12v to that wire with a test lead
Then see if it starts charging
You have a short somewhere IMO or a faulty ignition switch possibly
You know how that idiot light works right?
There is power to the alternator or battery lamp and the other side is ground at the alternator (that turns on the light)
Then when the truck fires up and the alternator takes over, there is +12v on that wire and no ground path, (that turns off the light)
So, question? Is the lamp coming on when you turn the key to on?

 

I’ll take a look at that next time I get a chance to work on it

 

Thanks for everyone one that helped, I’m swapping in a 460. So now I am done trying to figure it this alternator

 

That'll probably fix everything for sure.

 

I think too lol