Left Brake light problem.

I have a 97 F150 with the towing package. My LEFT brake light goes out when I use my RIGHT trun signal is used. All of the other conditions work correctly. Has anyone had this problem, if so how did you correct the problem?

Reply to
Hammer
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That sounds like a bad turn signal switch - the brake light leads go through the turn signal switch to determine steady (brake) or blinking (turn) indications. If the brake contact sending brake light power to the left lamp goes open when you select right, that would do it.

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Reply to
Bruce L. Bergman

Hi,

I had the same problem with my e150. Got pulled over 2 times and was told to fix it. I finally started to take a look at it. Sadly I couldn't figure it out on my own. After checking everything with a continuity tester and it all checked out, and looking in the book and wiring diagram, it still had the problem. I took it to a mechanic, and he found a short in the ground. All he did was cut off the old socket and put in a new socket on the side that was acting up. And that is not the only time an electrical problem was some kind of short to ground problem. In this case all that needed to be done was replace the light socket. I think the socket was 3 dollar part or something.

Reply to
waterskiing greg

You probably have an open ground in the right tail light....

Reply to
Jim Warman

Not a short to ground, a bad ground - open ground, high resistance ground, or intermittent ground.

Reply to
clare at snyder.on.ca

Reply to
waterskiing greg

Thank all of you for your help. I started out to fix the problem by the parts chasing method. I started with the cheapest to the expensive parts. 1) Replaced rear light bulbs, no change. 2) Swapped the light sockets to try to move the problem, no change. 3) Replaced the Turn/Hazard/Controls relay, no change. 4) Moved the relays with the part number around to try to move the problem, no change. 5) Replaced the Ford's name Multi-Function Switch (Turn Signal/Hazard/Wiper Switch), fixed the problem. Bruce was correct, it was the switch. Again thank all of you for your help.

Reply to
Hammer

It kind of sounded like it was the switch, though the people that said "Open Ground" had a point - but usually there's much more 'general weirdness' associated with an open ground, like taillights and marker lights that go out or blink on the other side when you step on the brakes.

I cringed as you said you were working your way through it by replacing parts. "Throwing parts at the problem" can get really expensive really fast. Bulbs are cheap and probably due on general principles, but relays are a bit pricey, and those multi-function switches... If you're wrong, Big Ouch.

They don't take returns on electrical parts - and they shouldn't take them either, they have no way to know if you are being honest about never installing the part, or the problem was elsewhere and you blew up the new part trying to diagnose it. Or worse, you installed the new part, are handing them back the bad part and doing the repairs "for free".

(This is why I won't take an open box part that looks to have been installed once already - unless it's the last one, I REALLY need to fix the whatever, and the clerk notes that it appears to be used on the slip so I can get credit if it's Pre-Blown...)

For next time remember that you can use a test light to test the relays and switches, if you have a good wiring diagram so you know for sure what to look for and on which lead. You would throw the TSS into Right Turn, see that the power is coming in OK on the lead from the Brake switch, and not leaving on the Left Rear Stoplamp line like it should.

And for relays, swapping around works if there are multiples of the same model on the car. Just remember to tag them so you can get the right ones back to their original sockets.

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Reply to
Bruce L. Bergman

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