I spent all day yesterday trying to track down what appears to be a short in my electrical system. After all that it seems like maybe it's the factory computer itself of the EEC power relay. I ordered a relay, should be in on Wednesday. If that doesn't solve the problem I may be looking at getting a new computer. I'm going to look on e-bay right now. But I also have the potential of picking up a 1994 IDI Turbo F-250 - any chance they share the same computer? Mine is a 1990 F-350.

My battery idiot light came on on the dash. I had the alternator and batteries tested (both were new in the Spring anyway). They tested good. However, when I check battery voltage with the engine running I show just over 13v. When I put the headlights on the voltage drops dangerously close to 12v and keeps slowly dropping. I disconected all my batteries (I have an extra mounted on the back to run the accesories in my workshop in the box- 3 total batteries). I did the light bulb test and tracked the "short" to the starter relay on the passenger side by the battery. Figured out which wire had voltage (11.85v)(Big yellow wire) traced it to the EEC power relay. Pulled that out and it tested bad. My dad also pulled the computer - can't remember now what the reason was for pulling it. I rigged up a replacement relay - seemed to work. No run off voltage. But when we put the computer back under the dash the 11.85 volts came back. Not sure what to do from here.

Many thanks for any help!<!-- / message --><!-- sig -->
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On an IDI diesel, if the trans is an E4OD, there is a computer that only controls the trans and then only one other that controls the rear anti-lock brakes. So if your truck is gas then it will have an engine management computer that the IDI diesel does not have.
If it is gas you should post the problem on the `87-`96 F Series page where you will get plenty of help.

 

redbrutis,
Welcome to FTE and the IDI diesel forum.

What engine do you have in your current truck?
I can move this post to the correct forum so you can get better help.

 

My motor is the 7.3. I was simply confused about what the computer (PCM) controlled. The only thing stamped on the computer was EEC - I guess it has several names. Thanks. Still having an electrical problem, but I don't think the computer has anything to do with it.

 

The best I can decifer your post it may be a faulty regulator which is mounted on the fender well passenger side. The metal box the wires coming out of it controls the fielding of the alternator to adjust the voltage accordingly.
Not running you should have 12.6V
Running you should have 14.6V
Running with lights & acc over 13v

hope this helps. Also check all your connection to the reg and alt.

 

Thank you, I will give it a try.