Alternator problems with 4.0 swap

Mike P · Aug 9, 2007

Ive put a 4.0 from a 91 explorer into my 1986 b2. A new alternator was tested and put on during the swap and im having a problem with the alternator overcharging my battery. The alternator puts out around 16.5 volts and boils the water out of my battery.

I checked the I wire and instead of having 1 volt, like I believe it should, it has 3 volts. Am I right having the I wire of the explorer harness to the lg/r wire of the b2 harness?

AllanD · Aug 14, 2007

It's funny but most people think the big difference whan swapping a 4.0 into
an '88 or earlier RBV is the engine management when infact the engine management is more or less "self contained", where the complexity of the swap really lives is in the completely different schemes used for "power distribution" on the upto-88 and the 89-on vehicles.

LtGreen/Red-stripe goes to "I" on both the early style alternator and the late style.

Which type of alternator are you using? the '85-91 style "slip terminal" output or the later '92-98 "internal fan" screw terminal output alternator?

on my 4.0 swap I used the the internal fan alternator, my '93 engine came
with a 95A alternator, but I eventually (as-in last saturday) tracked down
recently rebuilt (Junkyard gold) 135Amp alternator.

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Mike P · Aug 16, 2007

Considering this is my first and only vehicle, I have no clue what type of alternator it is and heres why.

http://i47.photobucket.com/albums/f162/vbwavessuck/DSC01496.jpg

Judging by the red post id assume its the screw terminal and I've had it apart and it has some form of a fan inside, but what is screwing me up is it was a 91 explorer that this engine/alternator came from. Can you clear it up? I can take more pictures too if you need it

steiner_5000 · Sep 6, 2007

Thats strange becuase I am having similiar problems with my 4.0 swap except my alt is underchargeing. I pulled the motor and everything from a 91 explorer. Is that what you did. If you figure anyhting out let me know it mite help me. Thanks

CJREX · Sep 6, 2007

Hey, at least your 4.0 runs. Mine's still sitting in my garage :annoyed:

Don't know if this will help you but this is the Alternator info I have for putting the 4.0 alt into a Ranger/BII

The black and orange from the 4.0 alt that turns to grey after a fusible link goes to the solenoid just as it did on the ex. The old black and orange on the ranger is junk. Cut it. The old orange and blue is also junk. Make sure to cover the ends with shrink wrap or elec tap to prevent grounding out. The yellow and white on both side can be spliced and the green and red as well

AllanD · Sep 11, 2007

I've actually gotten to the point where I'm driving my 4.0...

I had NO underhood wiring problems, but then again I had BOTH EVTM manuals
TWO complete '87 harnesses, two complete harnesses for the '93 engine I was
using and I wasn't rushing, it took me nearly three weeks to do the wiring...

The problem I did have was a loose ground next to the PCM that prevented
the computer from controlling the fuel pump.

having the right manuals makes things much easier.

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Alternator problems with 4.0 swap

Mike P

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AllanD

TRS Technical Staff

Mike P

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steiner_5000

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CJREX

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AllanD

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