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Wire identification on a 90'

xjtrailrider

NAXJA Forum User
NAXJA Member
Location
Roanoke VA
There is a red wire that runs from the starter relay positive side, to and along the firewall to a 20 amp breaker mounted to the firewall beside the chassis ground strap and then goes downward at the vacuum booster. It looks factory, where does it go and what does it do?

Mine has been cut and spliced into a wire for a trailer brake controller by a previous owner. I'm hopeing this may be where my problem is with the cold miss/stumble and low idle that I'm trying to diagnose. Sorry I do not have a pic.

Its a 90' 4.0, AW4, NP231
 
I just checked my 1990 (4.0, AW4, 231, with factory trailer tow package) and I have no wire or circuit breaker like you describe. The only thing high on the fire wall near where the ground strap from the block is anchored is the MAP sensor on mine. Maybe you could just disconnect it at the power relay and see if the symptoms disappear. My bet is that you have after-market wiring as part of the trailer electric brake circuit.
 
The red wire and breaker is something added at some time, sounds it was for a brake controller and someone added a different one.
My 89 has the tow package but no brake control.

For your problem test the MAT, MAP and CTS sensors, I can email you a FSM if you want. Don't post your email address here though, PM me with it for security reasons.
 
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