Hand/Brake Warning Light ?

[ukdj]

Whilst fitting my carbon fibre dash, I thought I'd look into the non-working Hand/Brake warning light .... as the dash was out and access was easy etc, thought I'd check the pcb for issues .... Bu cannot see anything obvious?

Thought it might be the handbrake switch but haven't got around to stripping the interior for access yet also removing the brake fluid resevoir cap doesn't turn the led on either?

Tracing the circuit leads to +VE(12v) on the GREEN wire and -VE on BLACK/YELLOW wire curious that this -VE is seperate from all the other LEDS which share a common -VE on the BLACK wire?

See Pic ...



There is also a resistor bridging the +VE & -VE to the Brake LED any idea why this is here?

See Pic ...



Operating the handbrake / removing the reservoir cap does not operate the LED nor so I see a change on the GREEN or BLACK & YELLOW wires?

As all of the other LEDS operate on approx 2.5-3v I assume the brake LED is the same and that R4 is probably shot as I'm seeing 12v at the LED - I have substitued a 12v LED for the BRAKE circuit but this does not light either ??

Before I strip the interior to get to the handbrake switch does anyone have their dash top off that wouldn't mind checking voltage/resistance readings on this circuit so I can identify what I should be seeing?

Regards

UKDJ

[JWzed]

Hi. Are you sure you are looking in the right area. I have just had the same issue - no handbrake or low fluid level light. I concentrated on targeting both switches, low fluid level and handbrake. Both had corroded contacts. They are easy to strip and clean. Result.

[ukdj]

I haven't got to the handbrake as yet but have checked the reservoir cap and all looks good there but no light on the panel?

as I have the dash top off thought I'd check this 1st before stripping the interior to get at the handbrake just in case it is

the panel, hopefully someone can confirm my readings and prove that it is not the panel and I can move on to the switch if needed.

Regards

UKDJ

Edited by ukdj on Tuesday 11th February 13:13

[ukdj]

bump

[Cider Andy]

You have +12V at the LED itself which means the LED is faulty (but you've substituted a known good one) or there's no return path (via either switch).

The fact you have +12V either side of the resistor means the resistor is ok (ie. not open circuit)

Ground the negative side of the LED; if it lights neither switch is grounding or the LED is faulty. As you've replaced the LED, both switches are faulty or there's a fault in the wiring going to them.

[JWzed]

I still favour the switches being at fault. The low level switch is easy. Check you have 12 volts at the switch. If so then take the switch off the reservoir and check that it will function. Mine looked OK but wouldn't work. When I stripped it and cleaned everything thoroughly it worked right away and the low level warning light came on.
However the handbrake light refused to work. Taking it out of the car was a pain but again when bench tested the switch was at fault. It is easy to take apart and the contacts were corroded and pitted. Used a Points File to clean them up,( I am old enough to remember those!) and it was like new.

[ukdj]

Guys thanks for the input ....

After lots of dismantling and wire tracing over the weekend the problem was twofold with both of you finding the issues:-

1) handbrake switch had broken, the threaded part had snapped and left the switch dangling in the tunnel so no return earth to the PCB from here

2) broken wire (internal so not visible) also not providing the switched earth to the PCB

Regards

UKDJ

[JWzed]

Well done Paul. It's a good feeling when you get the result.