Board index Flathead Power-Technical Questions, Answers, and Suggestions Evo's Thru 99 Electrical problem - Brake light

Electrical problem - Brake light

Post Sat Feb 14, 2009 7:06 pm

Posts: 250

Another question on this late model 1991 FLT. The rear fender brake light went out and I replaced bulb with a "1157" bulb and brake light still did not work. The other element in the bulb for the running light does work. I have checked the wiring and found the brake relay under the seat is working and I have checked the receptacle with a multi meter at the rear fender light and get voltage when the brake is applied, but when I put screw the bulb in the brake light it will not come on when the brake is applied. I have gone out and bought a 2nd new bulb just to be sure and it does the same thing. Am I using the wrong bulb, I though I had always used a automobile "1157" dual element in this light. I am sure I am overlooking something very simple, any help appreciated. Thanks

Post Sun Feb 15, 2009 12:53 am

Posts: 1538

1157 is correct bulb for dual filiment rear light..I use auto 1157s' too.. no problem.

I would make sure the contact in bulb socket is making contact with bulb, that would seem to be the problem..

Especially since you report having power at the socket 'brake' contact. Can't be anything else IMO.

try pulling out the socket contacts a bit, &/or even pushing in the wiring under the fender behind the T light.

there is a spring behind the insulator..It may be stuck, & down a bit too far.
I like to coat the bulb socket insides (all over) with Dielectric grease, besides being good for contacts, it helps the insulator slide back & forth in socket when a bulb is removed & /or installed.

Hope that helps....

Post Sun Feb 15, 2009 6:34 am

Posts: 250

Hey Sleeper, thanks for the help. I did not know the contacts were spring loaded. If the brake light side contact is stuck in (I have pushed on the wires from under the fender and they do not move) am I right that I will need to remove the rear light fixture from the fender to be able to get at the contact and lube it. Thanks again.

Post Sun Feb 15, 2009 11:43 am

Posts: 1538
Might try spraying WD40 around in the socket first, that may help it to move.
Or try using a pair of needle-nose pliers to 'gently' grab that contact & pull it out just a tiny bit.

If it does move, then add the dielectric grease & work that in around the socket & insulator.
Ideally, you should be able to push in on the insulator & it come back out on it's own.
Total movement is generally no more than 1/4"..

If in doubt, inspect another light socket.

Should be able to free the insulater up w/out T light removal.

Post Sun Feb 15, 2009 3:42 pm

Posts: 250

Sleeper, I have lubed the sprung posts in the receptacle; however after noticing that it is sprung, I believe it was working before. It is popping out good. I inserted new bulb and it still does not work. I am going to the dealer when they are open (Monday or Tues) and buy another relay. Could something weird be happening in that relay when the bulb trys to pull the current through it. I will report back. Thanks, Buster

Post Sun Feb 15, 2009 6:57 pm

Posts: 1676
Location: Interlaken, NY USA

Might be Buster, or some connection between the socket and the relay has gone "resistive" in techno jargon. I.E. funk in a connector. Voltage appears at terminal, but can't pull current through. Otherwise, I'd say "Ole Doc Billy" has walked you through all the right steps. :lol:

Post Sun Feb 15, 2009 7:12 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

I agree with Doc....if what Sleeper instructed didn't solve the problem, there is a loss of continuity between point a and point b. Pa

Post Sun Feb 15, 2009 11:49 pm

Posts: 1538
Ok Buster-

Now we have 'Dr Dick's input.. Always a good thing.. :!:

PS: Most stealers are closed on mondays...Least around here..

But the auto-parts should have what you need,
I think it would be a 15 amp. check yer manual to be sure though...

Last edited by sleeper on Wed Feb 25, 2009 6:32 pm, edited 1 time in total.

Post Thu Feb 19, 2009 1:33 pm

Posts: 250

OK! I have the answer. I got a new relay and the brake light now works. Don't understand why I was getting voltage through the brake light terminal on the rear fender light, but for some reason I guess old relay was not allowing the load from the bulb through the relay. The old relay even "clicked" when you hit the brake lever. I went to Auto Zone to buy this relay and they cross referenced it to a GM antenna and/or headlight relay for $16.99, however did not have it in stock. Went to the dealer today to get the harley version and they charged me $10.00. Not sure why, but didn't argue with them. Sleeper, Dr. Dick, and PA; I appreciate your help on this!. Thanks, Buster

Post Sat Feb 21, 2009 1:56 am

Posts: 1538

Glad you're brake light is working again....

The old relay/breaker should not click when activated. Unless it trips it off.. Then ya hear the click..I'm thinking it only clicked when the bulb was in the socket...That was the load it could no longer handle. Otherwise ya had juice.

The new one does not click, does it..

I think this may be a case of an anemic relay/circuit breaker..Growing weaker.

Return to Evo's Thru 99