Alternater Problems with swap

steiner_5000 · Post by **steiner_5000** » Wed Aug 22, 2007 10:11 am

I just did another 4.0 swap in my 85' B2 as some of you know by now. Anyway I'm having charging problems with my alternator. Whats happening is the alternator isn't putting out any voltage. I'm getting 12 volts into the alt. and exactly the same amount out. I am POSITIVE the alt. isn't bad because I have two that both tested to be good and am fairly sure the wiring is hooked up right. The only thing I can think of is a ground problem. Any Ideas? I really am greatful for the help.

steiner_5000 · Post by **steiner_5000** » Fri Aug 24, 2007 11:19 am

Is it possible that the main ground isn't good enough. I have the ground cable from the battery going to the engine block then to the body but nothing going from the block to the frame. Will this work?

Post by **Nobody** » Fri Aug 24, 2007 12:49 pm

The ground cable should go from the Battery to the frame, then to the block. Then there are couple straps that go from the body to the frame. However I don't think this is your problem.

Sounds like your alternator isn't getting power to the Stator terminal. This could be from being hooked up wrong, or possibly a bad voltage regulator. I'm assuming the 4.0L uses the same charging system.

The alternator needs 12V to the STAT terminal to make power. This voltage basically turns the Alt on and off. I believe stock BII was a white wire, but I'm not positive.Then of course the large BATT cable and Ground. There could also be another terminal for the electric choke (I ?) which sends something like 9V to the choke only while the engine is running. With fuel injection, this of course wouldn't be used.

DBrown · Post by **DBrown** » Mon Sep 03, 2007 5:38 am

if I remember right...the only wires I hooked up on my alt were the large black wire with an orange stripe to the same size/color wire from the fire wall, and the small green wire with a red stripe to the same on the factory harness. the thicker yellow wire I just tied up and capped off. hope this helps...

ranger5.0 · Post by **ranger5.0** » Mon Sep 03, 2007 1:00 pm

If I recall correctly, 85 was externally regulated, and your 4.0 one would be internal. Something to think about in how it was wired.

steiner_5000 · Post by **steiner_5000** » Tue Sep 04, 2007 7:06 am

So what does that mean I need to do. Do I take the black/orange and the green/red wire over to the firewall like DBrown said or what? Will the ground strap from the frame to the motor change anything?

DBrown · Post by **DBrown** » Tue Sep 04, 2007 1:34 pm

it realy depends on what year truck you have and what year motor/harness you are installing. my stock harness had those wires going to the previouse alt and the 4.0L had the same wires comming from it. so I looked at the wiring diagrams and and connected the wires that made it work. if you do not have the diagrams from the truck DO NOT just start connecting wires.

the way I wired my truck was ro connect one system at a time. meaning, charging, fuel pump, ing., and so on....

when you break it down like that you tackle alot of little problems instead of all of it at once. does it take longer...yes, but it is less confusing

steiner_5000 · Post by **steiner_5000** » Wed Sep 05, 2007 1:51 pm

I completely took the old wiring harness out of it and put in the complete 4.0 harness out of an 91 Explorer. I still have all the wires in the firewall from the old harness though. I have the large black/orange wire going to the battery side of the solenoid but the green/red wire isn't wired up. Would it make a difference because I know the wire is for the ammeter. Does this sound right?