I'm new here...need some help...54 F100 with 350/4spd and stock everything else...sits in the garage for long periods of time...an interesting quirk has developed...the brake lights tend to stay on all the time...sometimes I can mash the brake pedals 3 or 4 times and they will go off...after that they will mysteriously come back on by themselves sometimes...I changed the switch...didn't make a bit of difference!Is this a brake problem or an electrical problem?Thanks!

 

Is the brake light switch in the master cylinder or a linkage to the pedal? If it is in the master cylinder it is probably broken internally sticking in the on position. Ford had several years where the switch would leak internally and actually cause a fire because contaminated break fluid (or possibly even clean brake fluid ) would cause heat build up . (My 1994 F150 had that- I was changing my oil and the switch on the master cylinder started to smoke! - I am sure it was a lucky coincidence but kind of exciting none the less).

 

The switch is in the master cylinder,which is on the frame under the floor...there is a tailpipe right next to it...I wonder if it IS a heat related issue.It is almost 100 degrees today...but this happened last spring,too...maybe it's the tailpipe.Might be time to fabricate some kind of heat shield.

 

If it were me I would replace the switch and make sure there is a fuse in that circuit on the supply side. I would also fabricate a heat shield. both are simple projects and worth the time.

 

Some of the new switches aren't any better. I finally broke down and got one from the local Harley Davidson dealer. His parts jockey didn't know what I was talking about, but his mechanic finally got him straightened out. Prior to about '92 HD used a similar switch with the same 1/8" npt thread and made in the USA - and cost accordingly.

I've had no problems since......... fwiw

 

Would that be the 71-up rear hydraulic brake light switch for XLCH,etc.that runs about 22 bucks?

 

If you swap out the switch and that doesn't help, take a very close look at that continuous hot wire (even when the ignition is off) and see if its touching any other wire. This happened to me back in the spring and ONE single strand had fallen over on the wire going to my tail lights. It drove me crazy because my lights would not turn off unless I pulled the battery cable.

 

That's what I've been doing...pulling the battery cable...can't find anything like the stray wire thing...I think it might be the heat thing...gonna check out the plunger,too...there is zero travel in the pedal!

 

replace that 350 C....Y thingy in the engine bay, that should fix it LOL John

 

...that was in it when I bought it...like to have a Y-block at some point...till then...

 

Ok if that's the case, it sounds like its a brake fluid pressure issue. Especially considering you can pump the pedal and turn the light off by building the pressure back up.

 

Don't knock the darkside it's as fun as the wildside! We have cookies....

 

Aw, i was just messin around, after all i am putting a Lexus in a COE. Cant get a lot darker than that IMHO John

 

LOL... I'm just playing... Have you used the arm on anything else on the truck? Still would like to look at your frame points with the arm.

 

That sure sounds right. I can't find the pn this evening but I'll keep looking.
I know I wrote it down somewhere so I wouldn't lose it : )