memyselfandI

Ok, I let her sit too long and am now paying. When I parked her everything worked, 9 months ago. I'm getting ready for a safety inspection and noticed the right rear light was dim. I ended up replacing both sockets and bulbs, and the lights are all brighter now, but the rear lights are acting weird and was doing this weird stuff before I changed the sockets and bulbs.

Hit brakes or hazards, only left brake light works
Running lights both work
Left blinker works but flashes fast
Right blinker works but fast
Either blinker and hit brakes, they both work correctly

My right brake doesn't work unless I'm using my blinkers, it doesn't work with hazards on.

Is there two flasher units for separate functions or is one of the switches( hazard, flasher, blinker, brake) going out?

Any help would be appreciated.

lairdt

I ran into something kind of similar with my '77 F250. I had to replace the brake light sockets due to water & corrosion causing shorts in the system, especially when it rained.

Tom.

vjsimone

Never hurts to replace the flasher, don't know the 77, but by 80' it was 1 flasher for both functions.

Flasher is in not the fuse box in 78'

The Hazard Switch may be an issue, exercise it a bunch.

JonWalter

Hey,a bit different question about 78.
i have a 1978 F-100 Ford with a flat 4 way plug already on truck. i am buying a trailer with electric brakes. how do i wire or make the 78 ford able to use the trailer brakes? do i have to re-wire the truck so the electric brakes will work? if so how do i do that?
Thanks!

fordguy2100

I don't believe 4pin provides a constant hot wire for trailer brakes. I believe you need at least a 5way plug. But I would buy a 7pin adapter. Wire up the extra wires and be good to go. Or just rewire a 7pin plug into your truck and if you ever need the 4pin again you can buy a 7pin to 4pin adapter.

Edit* here's a wiring diagram. Notice the 4pin is the only plug that doesn't have a trailer brake wire.

Now some brake controllers have a wireless handheld controller so you can run a 4pin plus the handheld brake controller. Just preference on what you wanna do I guess.

GFBurke

Same weirdness when I went to LEDs all around on the 79.
The PO switched the signal wire with the ground wire. Worked fine with incandescent bulbs (how? idk).
But with LEDs, ^ that type of weirdness.