brake lights

[LotusJoe]

I have had some experience with this area, even making my own DB10 Relay substitute, described in Lotus Europa Central.

The brake, hazard and indicator functions share common wiring from the relay to the bulb, so if the indicators are working there's little point in trying to trace a problem there.

Try this -  test the brake lights with the Hazard Switch in both the On and Off positions. I think that if the switch is On, but you have a faulty hazard flasher unit, you will get the symptoms you describe. Worth a shot, anyway.

[Roger]

Gone Quiet now. It'd be nice to know if the problem is resolved, and what was the solution.

[hey_kramer]

I'm having the same problem here as of just last week with my 73 TCS. Brakes lights stopped illuminating, however rear hazards, rear turn signals, and reverse lights function as normal. It's simply not detecting the brake pedal push. Fuse box fuses are OK. Traced it to either the brake switch by the oil dipstick, or the relay under the steering column. My money is on the brake switch (which has a mechanical component, yes?), because I think it may have been damaged when I had to absolutely smash the brake pedal into the floor to stop the car when some air got into the brake lines. Perhaps pushing the brake that hard that quickly (i.e. increasing brake fluid pressure too fast) broke the switch?

[BDA]

You can use a test light to see if the brake switch is completing the circuit. If it is, then it might be the relay. You can test that in a similar way.

Good luck! Let us know what you find out.

[hey_kramer]

You can use a test light to see if the brake switch is completing the circuit. If it is, then it might be the relay. You can test that in a similar way.

Last night during my initial inspection I depressed the brake with a piece of lumber and used a multimeter to see if any juice was traveling from post 1 to post 2 on the brake switch. The reading was 0.0. I did NOT yet test to see if any juice was even arriving to post 1 of the brake switch as delivered from the relay (which I'll do tonight).

[jbcollier]

Do yourself a favour and get a 12v test lamp like this:

http://www.benzworld.org/forums/attachments/w163-m-class/581802d1380320782-ml270-cdi-reversing-lights-not-working-test-light.jpg

Test lights put a light load on the circuit and are a much better indication of the quality and quantity of the voltage present.  Digital multimeters can often sense a full 12v on the circuits with corroded connections and frayed wires, easily confusing newcomers to electrical troubleshooting.

PS: fused, switched power goes to the brake light switch.  Hydraulic pressure closes the contacts and then the power goes to the brake/signal control unit.

[blasterdad]

Check your ground wires also!

[hey_kramer]

Traced it to the brake switch. Using the ohmmeter function of my multimeter, I disconnected all the wires from the brake switch and depressed the brake pedal. The circuit didn't complete, hence faulty brake switch. How might one of these go bad? 

[BDA]

I had an oil pressure switch go bad which caused it to leak quite a lot of oil. I don't know what they look like inside. If there is a diaphragm, it could have enough of a leak so that it it would not activate the switch but be contained so you didn't lose pressure. Just a guess. After you get your new switch, try cracking it open to see if you can find out why it didn't work. It'd be interesting to find out what happened.

[EuropaTC]

I've never had one fail internally either but like all mechanical things no doubt they do go bust. I've had one corrode at the contact tab which meant a new one, but otherwise they've been reliable. Does shorting the switch out put the lights on ? I guess that's the 100% confirmation for a duff switch. A pain to replace if it is the switch, but on the good side your car gets new brake fluid 

Brian

[hey_kramer]

Brake lights fixed! Swapped the brake switch with a new one, bled the system and refilled. Ta-da! But of course, it's rarely THAT simple...discovered the bleeder screw for the right drum brake was snapped off. Spent nearly 5 hours extracting it before I could even start bleeding the lines. But good now!

[BDA]

Glad you got it fixed!