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I have a 78 f150 4x4 straight 6.

This problem occured after replacing the starter solenoid (on the fender) and a couple of fusible links, so I assume I must have mixed up a wire somewhere, but I've spent hours troubleshooting and can't figure it out.

Problem: When running, the alternator is not putting out, but the alternator bench tests fine. Also, the accessories do not work (wipers, fan, blinkers) when it's running. If I put the key into the accessory position (between off and run) the wipers, blinkers, etc. work just fine.

I realise that I probably will have to spend a long time with a wiring diagram and a multi tester to figure this out, but it's such a strange problem that I figured maybe (hopefully) someone else had had the same problem and could save me some time and frustration.

Thanks for reading, and any ideas would be very much appreciated.

 

make sure all your grounds have good connections, a ground wire not connected properly will do some odd things.

 

I had sort of a similar problem. Fully rewired my truck and when done it didn't charge right. Alt bench tested fine, battery was good. Replaced the voltage regulator and that fixed the problem.

 

Once again I am reminded that the simplest solution is often the correct one. By gently jiggling the key
with the truck running and a multi tester hooked to the battery, I was able to get the accessories going, and the alternator charging. I'm off to the auto parts store for a new ignition switch.