No brake lights on the truck

[ghostrider500]

Ok... to start off I don't know if my brake lights were working before I started what I'm about to describe below.

Bought a new to me car trailer and redid all the lights and made it a seven blade plug. I had a old bumper plug on the truck that was a six wired into a 4 flat that was plugged into the weather pack by way of an aftermarket "T" inserted between the connectors of the pack. Bumper plug was old and crusty and went about replacing it with a new seven blade. Already have a seven blade in the bed for the fifth wheel and works great. Stupidly decided to splice into the 4 flat wiring and then the orange and blue wires routed to the back from the factory. Spliced wrong and put right turn into ground. :mad2: Never checked brakes at this point. Popped the fuse at the dash 20amp. Rethought my hastiness and went back to the factory wire harness that the fifth wheel plug is connected to and did it right this time. Everything works except for brake lights. Have tails, turns, 4ways, but no tails. This is with no trailer plugged in. Checked 20amp fuse at dash and is good, replaced it anyway and still no brakes. Looked at the brake relay, but not sure how to test it. did give it the sniff test and didn't smell burned.
The thing that has me confused is that my third brake light works and my brake controller recognizes when the pedal is engaged when a trailer is plugged in. I've replaced the brake position sensor(?) that is under the dash about five years ago and when it quit I'm pretty sure the third brake light and brake controller didn't work either. My questions would be:
1. Third brake light and brake lights are connected?
2. How does one test a brake relay or is it just easier to replace?
3. Brake position sensor bad test? What a PITA this was to replace.

Any and all anwers appreciated.

 

[btfarm]

There may be a ground that was a weak connection before you overloaded the circuit and now it's open

Sent from my SCH-I535

 

[ak diesel driver]

Check to see if you have power back to the circuit board in the taillight housing. If so you may have popped them

 

[Will L.]

Your brake switch or brake position sensor should be ok. If it were bad the third brake light and trailer brakes would not work. I would put in a new relay, worse case scenario is you end up with a known good spare.

If you don't have one, a power probe 3 is a beautiful thing for these situations. Throw something in to hold the brake pedal down, remove one taillight and check there for power and ground. Chase the missing item. One of the inductive testers (like the one for Christmas lights) is a fast way to go through the harness.

 

[Big T]

I have one of those 7 point plugs and it also has the flat 4 plug alongside, so it handles both.

 

[ghostrider500]

Fixed it at last

I learned a very important lesson through this; never rush a job.

I started by swapping out the relay which didn't change a thing. I decided to replace the brake switch and didn't bother to diconnect the batteries as I didn't think power was on constant here. Touched metal with the harness and got some sparks. finished the replacement and now I had absolutely no lights. Found that I had blown the 30 amp big fuse on the AUX post. Replaced it and still had nothing. checked the rest of the fuses and found that my F1 fuse was blown. I didn't realize this one existed; earler I had seen that my F18 was blown and didn't really look any harder at the the rest of them. Replaced it and voila!, had all my lights.
Long story short I'm not really sure what was the culprit, but I'm pretty sure it was the F1 fuse I had overlooked at the very beginning. Feeling pretty foolish about the whole thing.

 

[btfarm]

Feeling pretty foolish about the whole thing.

But relieved in any case...
Glad you got it :thumbsup:

Sent from my SCH-I535