Hey yall. Im new to the forums. This past friday i bought. 1978 f150 custom. It has a built 351w and a c6 tranny. Sweet truck. Picked it up for $2500. Here is my issue. When i have the head lights off... The blinkers work... When i have the headlights on.. They dont... And the driver side tail light is extremly dim. Im decent with electronics. But im no pro. Any ideas or suggestions would be great. Thanks in advance

 

Clean all the sockets & bulbs, especially the rears.

 

X2 on that and the grounding points back there, behind the taillight lens. Clean the headlight main elec connector, and use some dielectric grease on all elec connections after cleaning. Ck the harness going under the cab down the dvrs side inside frame rail for chaffing or damage. You might look into replacing the headlight switch after all the other stuff is done.

 

I started having turn signal issues a few months ago and finally had the time to replace the front turn-signal sockets with new ones I ordered. Now the bulbs fit very tight, as they should.


I am now having the same exact problem you have. Headlights on: turn signals don't work. Headlights off: turn signals work but the rear driver side is dim. We removed the ground wire and sandblasted the mounting point. Then we found out that the ground in the socket was not any good. We ran a ground wire straight into the light socket (bare wire) and the bulb worked.


When I got home I ordered new rear bulb sockets. I plan to go through all the grounds and clean all surfaces and then reconnect the grounds. I'm hoping this remedies the problem but you never know.


I'll let you know if I find anything out for certain but I would definitely start with making certain all 4 light sockets are securely holding the bulbs. My new ones have zero wiggle room in the bulbs. Also make sure they are all making good electrical contact. For as cheap & easy as the new sockets are to buy and install I would just advise you to change all of them out.


Here's are links to the one's I've ordered already and the rear ones I ordered yesterday. They look the same to me but have different numbers:


Ford - Ford Pickup Truck Tail Light Socket & Wires - Plastic Socket With A Foam Seal - Macs Auto Parts


Ford Pickup Truck Parking Light Socket & Wiring - Plastic Socket With Foam Seal - F100 Thru F350 - Macs Auto Parts


Good luck.


Dennis

 

Thanks for this bit of advice. I spent about two hours yesterday replacing the sockets in front, and doing several other things but on my next day off I'll check this.


Dennis

 

If could be a sure sigh that the PO had a cobbled up trailer plug mod/tird into the tail lights going on up under there.