Brake Lamp warning light on dash

Post by **vanzep** » Sat Jan 16, 2016 3:06 pm

Just been out in the 4th gen BB1 and the brake lamp warning light on the dash has come on. It goes out if you switch the ignition off but reappears after a few miles. Can feel anything wrong with the brake other than they do need replaced and have a fairly big lip on them which lightly scrapes most of the time but doesnt bind.
Checked and all brake lights working ok including the high level one

Going to have a look at the manual but wondered if anything else i should check...

The front discs are quite worn and have a lip on them so was going to replace them anyway but ive no experience of the fully loaded BB1 with tcs,abs etc so on a steep learning curve. I thought the brake lamp warning light only came on if there was a blown bulb!

Post by **Vtecmec** » Sat Jan 16, 2016 3:13 pm

Or low fluid, or a short in the rear light gubbins.

Post by **vanzep** » Sat Jan 16, 2016 3:18 pm

thanks for the pointers Vtecmec

ive been in at both items you mention in the last few days

well i checked the brake fluid level yesterday and all is fine-fluid looks good and to right level
and
i have been working on the rear lights and replaced both in the last week or so as gaskets were shot so could be a problem there but brake lamps are workings in both of them - will go check there isnt a trapped wire or bad connection

GJMHONDA2012 · Post by **GJMHONDA2012** » Sat Jan 16, 2016 3:22 pm

My bb1 had same problem last year, brake fluid level etc was all good, all lights were working fully but light kept coming on and would go off if u turned ignition off and back on I fiddled about with the rear light units in both back lights and it's not come on since, I replaced the brake light bulbs even though the old ones still worked but I would start with the wiring in the light unit first may be a slightly loose connection and when u hit a bump or something it will cause brake light to illuminate

Post by **newkid** » Sat Jan 16, 2016 3:27 pm

Discs thin, pads right down? Be knocking the level to far down when braking. Get them changed asap.

Post by **vanzep** » Sat Jan 16, 2016 3:36 pm

cheers chaps - very helpful

will get it sorted

just glad its not tcs,abs related
im a bit paranoid about having all these extra electrics and ecus on the BB1

mercutio · Post by **mercutio** » Sat Jan 16, 2016 4:49 pm

might be the tell tales in the rear light clusters

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sat Jan 16, 2016 5:16 pm

They're reliable old beasts vanzep, don't worry

To set your mind at rest...

TCS is extremely simple on 4g's. Doesn't interface with the brakes at all (except I assume to take a speed signal from the ABS ECU - don't know for sure though 'cause have never been able to get hold of a copy of the wiring diagram! However... Either way, it has no feed back into the ABS or brakes). It sits in the PGM-FI ECU and all it does is cut power if you get wheelspin. No braking to try and counter it like you might get on a more modern car.

ABS system is separate to the main brakes also - the only place they are 'joined' is that the fluid lines from the master cylinder, pass into the modulator block and out the other side to the calipers. nothing electrical is interlinked though and the fluid isn't mixed.

EDIT: actually not true on the ABS electrical front... The ABS ECU takes a feed from the brake pedal switch that feeds the brake lights at the back of the car (presumably so it knows when you are braking).
It is also on the same circuit as the handbrake and brake fluid level switch (presumably so it knows if there is a 'fault' on those lines). Both those last 2 switches are on the same circuit and drop to ground to put the light on, so unless the ABS ECU fails in a big way internally and shorts that pin to ground, it still can't put the brake light on.

But... That does suggest another possibility for the brake light being on, is the handbrake switch.

Post by **vanzep** » Sun Jan 17, 2016 4:22 pm

Glad to report it has sorted itself out

I did disconnect the battery to clean the terminals and fix a loose connection - so maybe it was just resetting itself - anyway looks like problem solved.

If it does reappear then i know what to check

Post by **vanzep** » Wed Jan 20, 2016 4:15 pm

It reappeared and turned out to be very low pads on passenger side which had been binding a bit. This had caused the fluid level to drop below the min mark when braking putting the brake lamp warning indicator on - clever car

All sorted now as new discs and pads fitted today thanks to @newkid