85 with some electrical issues

[Rhurley1]

Just picked up an 85 K5 with an 88 tbi swap in it. Picked up the truck 2 weeks ago drove it around with no issues. Then the headlights flickered and shut off. they never came back on. a few days later took the truck up to the trail and half way up lost battery charge.

So get it back down here and replace the headlight switch which does nothing. Dig a little deeper and find a fuse in line. burnt up. the fuse was part of the TBI harness. look at my fusible links and they look rough. So i went to the parts store and got a few new links coming off the starter and replaced them as well as the burnt up fuse. Also decided to get a new alternator because i figured that was the dead battery problem.

Now, hook everything up and the alt is SCREAMING. unplug the 2 tab plug off and it stops. plug it in and bam screaming. IT is internal of the alt too. not the belt.

on the plus side. headlights now work.

 

[rebelgregory]

Do you have an amp probe to see how big the draw is?

 

[Rhurley1]

I do not......

 

[Rhurley1]

Bump. Any ideas? What do the 2 plugs on an alt do or go to?

 

[diesel4me]

Those 2 wires provide voltage to the field coils inside the altenator to "excite" them and allow it to produce a charge..
Usually those wires are one red, and a tan ,brown,or white one, and the thicker red one is connected to the #1 terminal (that is marked as such on the back of the case)--it is always "hot" and gives 12V to the regulator..
The tan,brown or white smaller gauge wire also provides 12V to the #2 terminal on the regulator ,but it is only "hot" when the ignition key is in the "on" or "run" position..

My guess is you still have a dead short or a heavy load being put upon the altenator,that will make it work very hard and they can make a squeal or whining noise under those conditions...better not run it for long while its doing that or it'll eventually fail and burn up inside...it could be the regulator inside the altenator is getting its field terminal grounded ,that will also make it put out maximum output...

If your battery was dead or nearly dead when you got the truck fixed,it may have just been trying to recharge it--its best not to let an altenator bring a battery back from the dead--charge it first--the altenator is more of a "battery maintainer" than a battery charger...

 

[Rhurley1]

That sounds like exactly the case!!! I have the battery on a charger today actually. It was squealing when the battery was dead. Il try it once I get home and have a fresh charge.

 

[diesel4me]

I would also check to see if anything is drawing power from the battery when it is not running by taking the positive battery cable off,and out a 12V bulb between the cable,and the battery post--if the bulb lights up brightly,something is drawing juice that should not be..it may glow dimly ,thats fairly "normal",as your radio and clock may use a bit of power (so the radio wont lose its station "memory" pre-sets,and the clock is always "on".)..

If the bulb lights up brightly,you can start taking fuses out one by one,to see if the bulb goes out,that will tell you which circuit has the drain...other things could be sucking juice too,like the altenator itself,it one of its 3 diodes inside fails--un-plugging the 2 wire plug will put the bulb out if its that causing the drain...