I converted my 1985 carbureted F-150 to Duraspark Ignition. I am getting rid of the HUGE bundle of computer wires that runs to the firewall. The computer is mounted under the dashboard just under the steering wheel. Do I need to retail ANY of the wires in the EEC-IV computer wiring harness? When I say computer harness, I am referring to the HUGE bundle of wires that is attached to the firewall on the driver's side, to the left of the steering shaft looking under the hood. I have eliminated all but 3 wires:

1. A black wire that has a "Fusible Link" written on it that turns into a yellow wire that goes from the starter relay to the computer harness. I unplugged this one, and nothing seems to have changed at this time.

2. A green wire that goes from the air conditioner to the computer harness. I have no way of testing this one because my air conditioner is not working, but I do want to fix it next year sometime.

3. A black wire that is attached to the negative battery cable and it also goes to the computer harness.

And finally, how do I get all of those now useless wires through the firewall to the interior, so I can remove the computer?

 

I'd remove the plugs on the end of the cables, the connector comes apart. That should let you snake the wires back through the firewall. Also have you tried to run the truck without all of the wires in place? Try the lights and everything, you'd be surprised at what is interdependent on a computerized truck.

 

#1 and #3 are power supply wires, you can eliminate them.

#2 was the wire so the ECU could control the air conditioner. Basically it cut the compressor off when you floored the gas pedal. Usually it grounded or ungrounded a relay that controlled the compressor clutch. So you may need to wire around this or possibly ground this wire to make the A/C work.

 

Thanks Franklin. It appears that #1 does not go to the computer at all, but to a module just above the computer under the dash. Do you have any idea what this wire was for?

This module under the dash above the ECU also has a yellow wire with green specs on it. This yellow wire was cut by accident and it doesn't seem to have any effect, but I would like to know what this wire went to.

The reason why I ask these questions is because somewhere down the line of removing wires to the computer, and accidently cutting the two wires mentioned above, I seemed to have lost my horn and my tach is now reading about 500rpms too high when my overdrive kicks in. Any ideas?

 

That yellow wire was a power feed for something. Sorry I don't have a good enough diagram for your year to tell you what the module is for.

I also do not know exactly were the horn relay is(some trucks did not have one) but if you could find it, you could troubleshoot the horn wiring from there.

Sorry I can't be more help.