Hey guys, I need someone to verify something for me. My truck is a 78 f150 2wd 6cyl standard transmission. My right rear brake light/tail light is acting up. If I hit the brakes it just goes out vs getting brighter and when I use my left turn signal it goes out as well without me hitting the brakes. The right turn signal works fine. I remember in another vehicle I owned the brake lights run through the turn signal switch. Is it the same on this truck? Is there a flasher fuse that could cause this? Thanks guys

 

There is a flasher, but I would be more apt to believe you have a short or a bad turn signal switch.

 

Ok that's what I thought, because there's two flashers arnt there? One for the front, one for the back? Didnt think it would be possible for it to quit halfway lol

 

It should just have one flasher

 

Grounds. Remember, turn signal circuits run to both ends of the truck... check all the grounds at both ends, and check that the sockets themselves are connecting to ground - it is not unusual to find you have just cleaned off the sheet metal and ring connector, to discover the wire to ground strip connection inside the socket is crap. Make sure these are 100% before going into switches or flashers.

 

As HoustonDave stated. I would start with the grounds before purchasing new switches. I just did this and it cured most of my lighting issues such as randomly going off. I'm still working on getting my backup light to work

 

There are TWO flashers.

Both flashers look identical, are round with two prongs, but the 4 way flasher is a H/D type, has a louder CLICK.

T/S flasher plugs into the back of the instrument cluster at the upper left.

4 way flasher nestles into a bracket that attaches to the backside of the dash (near the cluster) w/a screw.

 

Ok sounds good, I'll check out the grounds and see what they look like and I'll check out the sockets. As for the flashers I know my 85 had two so figured this would be the same. I'll dig in and see what's going on!

 

I meant only one for the TS, I should have worded that better...haha

 

Looks like the socket, the ground side in particular is pretty corroded. It did start working better once I popped it out of the assembly. It just dims insted of going out. I'm going to replace the socket when I get a chance and see what happens!