Rally Guy

Morning all - a helpful fellow motorist told me on the drive in that my brake lights weren't working. And it's true, they're not. I have a 1990 S2 - so I have a high-mount brake light as well as the regular ones.

None of them light up with the brake pedal pushed.

Parking lights DO work. Flashers/trun signals DO work.

I have ABS (and according to the fuse panel chart brake lights and ABS are on the same circuit - but I am not getting an ABS warning light on the dash (it DOES do the test illumination upon start up).

I have no other warning lights on the dash either.

Fuse tested okay. I don't have a multilmeter with me - so I can't test anything before the drive home.

Any ideas as to what's gone wrong?? (Yes, I've seached through 150 hits for "brake light" here - no luck)

Thanks, I'd like to see if I can fix this BEFORE the drive home in stop and go traffic!

RK

xsboost90

problem i had w/ mine- someone put one of those clips in the brake light circuit to draw power for a cell phone. When i deleted the cell phone, i guess the clip bent the tabs inside of the fuse box. I had to bend my fuse slightly in two different directions to get it to make contact..

ausgeflippt951

Check the brake switch aft of the B-pedal. Since the lights should go on when the switch becomes uncompressed, you can check to see if this is working by simply pressing on the brakes as hard as possible to try to trigger the lights to come on.

If still no dice, adjust the switch manually and try it by hand.

I highly doubt this is your problem, but if all else fails give it a try.

Rally Guy

Will check the switch. This is a high-milage car (approaching 300k kms) so switch could be the issue.

Anything else to check??

Thanks!

RK

austin944

If you can't fix it before you go home, just put your flashers on for the drive home and drive slowly, people will get out of your way or at least notice you more (except for the cell phone yakkers).

Mamooguy

Stupid question, but have you checked the bulbs? A short might've burned 'em out.

I'll also offer the standard piece of advice when addressing electrical issues: check the grounds!

Rally Guy

Oh - good call on the grounds issue! I've been messing about in the hatch area mounting a sub - could be that.

Anyone know where the brake light circuit grounds to the chassis?

As for the bulbs - can ONE bulb cause the whole circuit to not work? NONE of the bulbs lights up - not even the hi-mount one.

RK

ausgeflippt951

Occam's Razor: the simplest explanation usually is the correct one. Three bulbs all going out (near) simultaneously? Unlikely, but still possible. Most like is something to do with the fuses/relays or grounds.

Still, it's always ridiculously easy to check the bulbs, so why not.

Rally Guy

I'm a Occam's Razor advocate - agreed - bulbs unlikely.

Anyone got a wiring diagram of this circuit? Are there relays to consider? Where are the grounds and what other elements of the circuit are there?

I'd posit...

Supply from Batt ->Fuse box -> switch -> Bulb assemblies -> ground.

Missing anything?

RK

Mamooguy

I know there's a ground right by the port taillight (near the hatch release motor, if I recall). I think there's another one in the forward part of the hatch area (not sure about that one tho).

There are also ground in the driver's side footwell close to the brake pedal. It's awkward to get a good luck in there (gotta be on your back with a flashlight), but they're definitely worth checking.

Don't just check for broken connections, see about bad connections too.

There's a diagram showing all the grounds floating around somewhere, but I can't seem to find it.

pjburges

You might need to replace that switch on the brake pedal - Sounds like that could be your problem, that or a fuse, or a major grounding circuit.

Have any other electrical problems shown up recently, as this might lend to the idea of a bad ground somewhere, especially on a high-mileage car.

Rally Guy

No other changes to the car that I've noticed. You're right - it's high milage can lead to all manner of issues and it's due in for some serious service - but this is SO much of a safety issue and that I cna't drive arond with it broken.

I'll check those grounds and head home early to avoid traffic.

I'll post the outcome if I find out what's wrong - thanks for the help!

RK

Rally Guy

Okay - made it home safely - but an hour with the multilmeter hasn't solved the issue.

Here are my findings - really need someone with actual electrical knowledge to help now!

There's good voltage at the fuse. Fuse is okay.

Brake switch works fine - infinite resistance and zero resistance (open and closed).

The connector to the brake switch shows strong voltage IF I complete the circuit to a chassis ground (still doesn't illuminate the brake lights).

If I measure voltage using the connector's "Ground" wire - I only get a ready of 1.16V. Why? Is that normal? Or does that suggest a ground problem?

Other data points...

The parking lights work. The flashers work - so the grounds for the rear light clusters seem okay.

If I check the voltage the "purple with black" wire at the rear left harness connector to the lamp cluster - I think it's getting either nothing or a very low voltage. (No surprise, I think)

What do I check next???

Help!

Thanks,

RK

Jfrahm

All the bulbs being out is not totally crazy. Maybe all but one were out until last week. Ever flag someone down to tell them they only had one brake light? I had two out in my 3rd taillight before a friend told me, but I usually give my friends a good look at the back end of my car on a regular basis.

-Joel.

Rally Guy

Not only is that a plausible explanation - in this case - it's the RIGHT explanation!

On J's suggestion I just put a new bulb in a socket - and lo and behold - IT WORKS!

Turns out EVERY brake light bulb was burnt out. Problem solved - RENNLIST DOES IT AGAIN! YEAH!

Thanks to all for thier suggestions. I now know this curcuit a whole lot better.

RK