Brake Light Mystery

[Tony]

Just found out my brake lights weren't working. So I went through the steps. Fuse OK. Power to brake pressure switch OK. Removed bulbs, checked power back to bulbs; OK when brake pedal pushed. Bulbs checked OK with ohm meter. Insert bulbs, press brake pedal.......... no brake lights. Very strange and baffling. Running light filament of same bulbs work fine, just not brakes. Both have the same ground.

 

Anything obvious I am missing? Any thoughts? Got to be something simple.....

 

Thanks much.

 

Tony

Edited September 18, 2014 by Tony

[jlumba81]

Check the brake light switch. If its a caterham you can access it by taking the pedal box cover off. I've had to take mine apart and clean off the contacts.

[xcarguy]

Tony,

 

A few thoughts:

 

a) Did you check power at the bulb sockets or only power to the sockets?

 

b) Are you using the correct bulb for the brake light?

 

c) Run a jumper wire from the ground to somewhere else on the frame (just to be sure it's not the ground).

[Tony]

It was simple. Pumped the brakes a few times and then really pressed hard and the brake lights came on. Expect that the pressure switch is getting stiff and needs to be replaced.

 

Next question. Anyone know a part number for the switch? Nothing in the build manual about it. This is on a 1993 Caterham Seven. The pressure switch is mounted on a small cast aluminum block on the rear brake line, about one foot from the brake cylinder.

 

Thanks again.

 

Tony

[powderbrake]

I have an Ulralite, and replaced the hydraulic switch twice. Hydraulic brake switches are notoriously unreliable, particularly on a car that does't need much brake pressure to stop. I replaced mine with a mechanical switch actuated by the brake pedal.

[wemtd]

I think there is a low pressure switch out there (possibly VW) that activates at 30 instead of 60??? PSI. I believe this is a "take yours to the parts store and sort through their big book" situation.

 

let us know how you make out.

[xcarguy]

This is what I use; been running seven-years strong with no issuue and doesn't take much brake (pedel effort) pressure to activate:

 

http://www.summitracing.com/parts/prf-80174

[NVP66S]

I have an Ulralite, and replaced the hydraulic switch twice. Hydraulic brake switches are notoriously unreliable, particularly on a car that does't need much brake pressure to stop. I replaced mine with a mechanical switch actuated by the brake pedal.

 

Yea verily. Westfields use both depending on engine. My Mazda uses a mechanical switch on the pedal, but some others use a pressure switch. To further complicate the build, the manual described installing a pressure switch but the hardware provided was for a mechanical switch. I believe the auto industry as a whole is switching to the mechanical type. (pun intended).

[yellowss7]

This is close to what my 2000 caterham uses. http://www.painlesswiring.com/mobile/webcatalog/largeview.php?SearchField=80172&SearchAll=4x4 OffRoad OffRoad

Edited September 18, 2014 by yellowss7

[mca]

I believe I have the same switch as xcarguy (pressure switch from summitracing), and I am currently without brake lights. Running lights work fine, only difference with mine is they are oval LED brake/turn/parking light units. Does anyone know if the switch just completes the circuit between the 2 wires? So to test if the switch is bad, just short the 2 wires together and the brake lights should activate, correct?

[Tony]

So the car is so light and takes so little braking to stop that the pressure on the switch never makes it to the point of turning on the brake lights.......

 

Got to love it. Will be checking the recommendations for a lower PSI switch. Also may go the mechanical route, but would like to stay more original.

 

That switch from summit racing looks very close. Wondering if it is a direct swap thread-wise?

 

Thanks all for the many insights. For now I'll show braking with my hand.... Wonder if that will satisfy an officer of the law......

Edited September 18, 2014 by Tony

[coffee break]

You could tell the officer "I was down shifting, not on the brakes" :jester:

[NVP66S]

To me it's not so much what is legal, but rather what has significant safety merit. This is why I mounted an LED strip to my roll bar.

http://www.carbuildersolutions.com/uk/28-led-high-level-brake-light

 

Of course if your car is mostly for the track, brake lights are not so useful.

[scannon]

Yes or put a test light on the wire going to the light and see if it comes on when you press the brake.

[NVP66S]

Or put 12V on the wire leading to the brake and look for brake lights. If you do this with a fuse in the line, whether it blows or not will tell you if there's a wiring fault.