I have a '77 Bronco with a 351W and C4. I was having some problems a few months earlier with the lights flickering and after some reading and trouble shooting I found out I had the wrong Voltage Regulator. So after I replaced the Regulator everything was great for months....nice lights...no flicker....very happy! Well, yesterday I decided to fix a leak on the transmission. I started the truck and pulled it into the garage with no problems at all.....ran just like every other day...Perfect! I shut it off and proceed to do the trans work... the only electrical thing I touched was the neutral safty switch that bolts to the side of the trans. So I got it all back together and it won't start. So I thought it was the neutral switch...but no....after some carefull looking, under dash, and hood...I found out the throttle linkage going through the firewall that connects from the gas pedal to the throttle linkage bracket in the engine bay was shorting against the firewall. I know it sounds very strange. Because the firewall is supposed to be grounded! Well, come to find out when I put a test light directly to the battery ground and the other end to the body it lights up...?????? So confusing. I have all new HIGH QUALITY: battery, cables, regulator, alt. Nothing works in the truck with or without the key on. But, when I put a wire from the body to the ground everything works normal!..?????? It's like the body is positive instead of grounded....like everything is opposite. If I leave it with that wire it puts a small drain on the battery and I don't want it to drain it. Also...if the wire going from the body to the ground is hooked up and everything works good....I can start the engine and I can detach the wire and it will still run.....just no lights or anything else. VERY ODD! Please help....I spent all day on it...all i wanna do is drive my truck. I'd appreciate any help I can get....Thanks

 

I would first look for a short to ground under the dash.

The body should be ground to frame/battery also.

You would probably get some great info in the electrical wiring forum.
Good luck.

 

I figured it out.....turns out the voltage regulator was faulty. Well atleast so far. Gonna give it a good test tomorrow. The one that went bad was an electronic version. I now have a mechanical version. Does anyone know where I can find a Mechanical version? Also, does anyone know what the little condenser looking item that is sharing a bolt with my voltage regulator is? It has a flange and 1 wire coming out of it going to the voltage regulator plug. It looks in bad shape and I was hoping I could find a new one. I think it is unique to the '77. Thanks.

 

The cylinder thing is a condenser. It's not unique to 77. My '75 had one.

 

I believe that cylinder on your regulator is to keep the engine sounds and things like that out of your stereo and the rest of your electrical. Sort of a harmonic filter if you will.

J.D.

 

I believe the condensor is also unique to vehicles equipped with an ammeter guage and not just the idiot light. Not sure on where to get a replacement though.