I have an 86 F Series with a 302 and EFI. I've been having an electrical gremlin that is absolutely killing me.

I've tried searching and I'm not seeing anything so anybody who has any idea where to look would be very much appreciated.

A few weeks ago, my battery started draining while the truck sits. Replaced the battery, and it happened again. Ok, so it doesn't appear to be charging. Sure enough, the alternator was bad. I just replaced the alternator and battery, and went to start the truck. It turned over, ran for about 10 seconds and the motor cut out. No power, no interior lights, no ignition buzzer, nothing.

I'm not an experienced mechanic, more of a weekend warrior at best, and I'm now completely confused and discouraged. Every problem I've had up til now has been solved with searching this board and I hope you can help again. Does anybody know where to start looking?

 

First check and recheck all connections that were made to install both the alternator and the battery and any subsequent sub systems they connect with. Always seems like they find a way to wiggle loose. Start there.

 

A major electrical fault like that should be easier to find than some of the odd stuff, because it almost has to be a bad connection.

 

OK... I checked and rechecked those connections. It was all secure. I'll try to replace the wiring harness next and cross my fingers. Is there anything I could be missing?

 

The wiring harness??? Seems a little extreme, wasn't it running fine before?

 

I meant the wires to the alternator. My error, sorry about that.

But in answer to your question, yes it was running fine.

 

Does your alternator have an internal or external regulator?

I would start by checking/replacing fusible links.

 

It has an internal regulator. That's probably a better place to look then where my mind has been going on it.

 

Ford had major issues with the charging harness and plug on these alternators.
According to the TSB the plug and pigtail should be changed any time the charging system is serviced.

The rectangular plug should have two black/Orange wires that join a single fusible link attached to your fender mounted starter relay.
Fusible links have a little rubber 'tab' at one end.
If the insulation looks blistered, pull on them to assure the wire inside is still in one piece.

 

Had a similar problem on an '84 F150, no power to anything. Turned out to be a corroded connection (actually corroded away) inside one of the plugs. It was the major power wire (not sure what it is called) to the cab. Friend found it by probing wires with a multi-meter. Wired around the plug and away it went.

 

Well, just an update, I've got some new plugs and wires for the alternator coming in.

Taking that piece of wire out, I disconnected a gray plug which is connected to the alternator wire, and looks to lead directly into the cab. All four of the copper connections inside were corroded off, and the housing itself was broken. Any idea if I can splice a new one of these or do I need to replace the whole wiring assembly into the cab? Also, does anyone even know what this particular thing is called? I can attach a picture of the (unfortunately very broken) part that's in there now if I'm not describing it well enough.

 

The entire Motorcraft OEM plug/connector/pigtail catalog is online.
There is a link in the stickies here or in the '87-'96 forum, I forget which.