rear brake light switch

[billzbubba]

I recently changed rear brake pads & flushed/bled the fluid. Now my rear brake light switch(I assume) isn't working. Anybody ever had this happen? Any ideas why it would all of a sudden go bad? Any ideas/bashing will be appreciated.

[DR_DEUCE]

You might have air in the line....check the switch by connecting both wires together, if the light comes on, the wiring is good. Bleed the brakes again. The switch works on internal brake fluid pressure.

[monkeyboy]

Originally Posted by DR_DEUCE

You might have air in the line....check the switch by connecting both wires together, if the light comes on, the wiring is good. Bleed the brakes again. The switch works on internal brake fluid pressure.

Does this mean there is no adjustment as to when the switch is activated? I just noticed that if I just barely pull in the front lever, the brake light comes on but, I've got a LOT of travel on my rear pedal before the light comes on.

[1949shoebox]

bleed the brakes

[Traakon]

Originally Posted by monkeyboy

Does this mean there is no adjustment as to when the switch is activated? I just noticed that if I just barely pull in the front lever, the brake light comes on but, I've got a LOT of travel on my rear pedal before the light comes on.

The front brake is a small switch located in the lever that changes state when the lever is moved off the switch head. The rear brake is a fluid pressure switch which changes state when the pressure of the fluid in the brake line press' the diaphram in the sensor switch. Two completely different activation systems.

[JustDave71]

bumping this instead of starting a new thread.

94 softail, just put in a new light and make sure the wires were clear. I'll double check, but I suspect the switch

used a tester and I get a light at one terminal and none at other terminal with brake pedal depresssed

does that tell me my switch is bad?

[JustDave71]

after further inspection I found that the wire that goes from the rear switch to the brakes frayed. I recently changed my oil and am thinking that the oil drain hose somehow caught the brake wire.

there are two wires red and orange and they were on one clip that was attached to one post on the switch. was workin fine so I assume that's correct?

heh...front brake switch hasn't worked in months. gave up on that one.

[JustDave71]

well NOPE. Went and got some new connectors and reattached the wires and still no brake light. bulb is fine. I can look up through the clear in the tail light and see one filament lighting up and the other intact but not lit when brake is depressed.

fluid level and brake pressure are solid. brakes are actually really good no air nothin

I don't see anything rubbed through anywhere or anything else

sounds like the switch, eh?

[Coolmaker]

Originally Posted by JustDave71

well NOPE. Went and got some new connectors and reattached the wires and still no brake light. bulb is fine. I can look up through the clear in the tail light and see one filament lighting up and the other intact but not lit when brake is depressed.

fluid level and brake pressure are solid. brakes are actually really good no air nothin

I don't see anything rubbed through anywhere or anything else

sounds like the switch, eh?

With key on, jump the two terminals at the brake switch to each other, if it lights then. The switch is bad, provided you have good solid brake pedal when pushing it..

[JustDave71]

here's a question

what exactly happens when these switches fail?

I am guessing that since it's a hydraulic switch the pressure closes it causing the circuit to be completed and lighting the light, but then when it fails the pressure just doesn't do it anymore?

I have nice solid brake pressure and last night I jumped the two wires together and the brake light did light up so must be the switch.

[Coolmaker]

Not necessarily, the contacts inside just get corroded sometimes and will not make the circuit.

[JustDave71]

Originally Posted by Coolmaker

Not necessarily, the contacts inside just get corroded sometimes and will not make the circuit.

corroded from exposure?

everything I've read says that these hydraulic switches are completely unreliable.

granted, this is probably the stock 94 switch so...hell...15 years for a $15 max part isn't so bad

glad it didn't cost me a ticket for a stoplight!

[Coolmaker]

Originally Posted by JustDave71

everything I've read says that these hydraulic switches are completely unreliable.

Wow, they have been around for eons and are very reliable. Don't know where you read that. Glad you figured it out. And yes, 15 years sounds like reliable to me.. LOL

[JustDave71]

Originally Posted by Coolmaker

Wow, they have been around for eons and are very reliable. Don't know where you read that. Glad you figured it out. And yes, 15 years sounds like reliable to me.. LOL

saw it stated more than once "online" but lost in the info.

but like I said...if this is the original switch then can't really complain

hopefully some day I'll have the money to rebuild this bike from the ground up, get the motor blueprinted, rewire, etc.

[93Horse]

For what it's worth

Service manual for 93 FLTC FLHTC models,, the front and rear stoplight switch "trigger" a relay that connects 12 vdc to the stoplight.