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I have a 1988 Econoline that I have swapped the drivetrain of a 1995 5.8L powertrain into. I am trying to get the cruise control working, however I am having an issue that I hope someone can shed some light on.
The wiring is wired as per this diagram. The issue I am having is that the tan/light blue wire is reading voltage with the key on. That wire is from the brake on/off switch, so I cut the wire to stop voltage from going to the servo through that wire. The issue is there is still voltage (around 10 volts) coming from the servo on that pin.
I tested the servo by installing it in my 1995 Bronco and the servo functions perfectly. I have tested every other wire for voltages and they act identical to my Bronco, except the tan/light blue wire.
What am I missing?
EDIT: I should add that I have removed any extraneous items from the F150 wiring harness. The van already had its original wiring in place - lights, gauges, HVAC, etc, so during the drivetrain swap I used as little as possible from the f150 wiring to get the engine, transmission, and rear differential to operate. I have been adding things back in as I go.
Thanks!
Last edited by Retrofire28; Jun 16, 2026 at 01:26 PM.
Which computer is running the truck?
1995 5.8 what?
If the donor was EEC5
Trying to get at whether the 1995 used a cruise amplifier or if it was contained in the processor
What harness are you using?
The donor vehicle was a 1995 f150 2wd. The computer that came with the donor truck is running it. I am pretty sure it is EEC IV, it uses OBD I for diagnostics.
I have the wiring harness from the donor truck running the power train, but retained the '88 Econoline harness for chassis power like lights, stereo, HVAC, etc.
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