camelman

Even if they worked fine before?

Alan

Well no if they worked fine before I'd assume at least 1 should still be OK - so check the fuse voltage top and bottom voltage (on the fuse holder part) with fuse in-circuit and brakes "on". I'd suspect that at least the top connection will show a very low voltage in operation. If that looks OK then test the voltage at the bulb ground side vs battery ground when the brakes are "on".

Alan

camelman

I get 12V at the bottom and 11.85V at the top of the fuse with the engine off. Seems pretty reasonable to me. If I turn on all accessories, then the voltage drops to 11V. When the engine is running I get 13.35V.

When I press the brake pedal, the voltage at the top or bottom of the fuse decreases by about 0.5V.

I got a new alarm too. The Brenskreis light came on and flashes with the key fully turned. That appears to mean a brake pad is low. I don’t know if it’s related, but I doubt it.

Thanks,
Camelman

camelman

Okay. I just checked voltage at the brake pressure switch on the master cylinder and the wire registers the same voltage as at the fuse. I think I have two bad brake pressure switches.

Mrmerlin

sometimes even new switches fail ,
swap in a new set and try it.

NOTE if you work fast minimal fluid loss will be experienced.
IOW you dont have to drain the fluid out to change the switches,
put a towel under the MC so the fluid wont run all over the place.
Put a dab of Loctite PTFE non setting pipe sealant on the threads of the new switches

camelman

I reached out to Roger for a parts order, so the ball is rolling. Thanks for the switch swap tips.

Alan

This seems too much drop - I'd clean the fuses holder and fuse tips.

Is that the right translation? I think BreMskreis is probably just Brake Circuit Warning. I don't think your car is equipped with brake pad sensors (a later feature). I think this is just detecting that only one brake switch is working.

Alan

Alan

duplicate