Brake Warn /Seat Belt Warn Light

[Shipibo]

I purchased an 80 911 SC and among other discrepancies, the brake/seat belt light does not operate. Does the system have a relay and how can I test the system? Thanks to all-Charlie

[Rick Lee]

I bought a used one for $20 somewhere and just swapped it out. 2 minute job.

[Shipibo]

Thank You for your response. Where is the relay located? I have no electrical schematics. Charlie (70Years old) Explains SOME of the ignorance.

[Formerly Steve Wilkinson]

Well, there are two separate bulbs, two separate systems. I suspect it may be because your seatbelt-warning system was disconnected by the PO and, an entirely separate issue, the contact on the handbrake assembly is out of adjustment. It's easy to adjust, there's a screw that holds it in position (visible once you lift the rubber boot), and you can move it up and down a bit till the bulb comes on with the handbrake engaged just one notch. Assuming your peanut bulbs are good, of course...whihc often they aren'.

stephan

[Shipibo]

Thanks, Steve. Will check the brake light adjusting screw. Do you know whether there is a seat belt relay?

[Formerly Steve Wilkinson]

I can't imagine why there would be relays on such low-power circuits. All you're doing is lighting a minuscule bulb.

Stephan

[Shipibo]

A buzzer takes considerable more current that the light..

[Formerly Steve Wilkinson]

Okay, you're right, I didn't know there was a buzzer. (I've never had stock seats in my '83 so wasn't aware of it.) Looks like you may even have the single-bulb warning light, whereas I have one each--brake and belts. There is a seatbelt warning relay shown on the wiring diagram, and my factory manual depicts it ("logic-relay for safety-belt warning system") as being foward of the instrument panel. It's not an ordinary-looking relay but is a larger rectangular silver box--I assume aluminum from the photo, but it could be plastic--and you can probably get at it by removing the tach and/or speedo.

Stephan

[Shipibo]

Will look, but that does me little good, I guess. Thanks, Charlie

[Formerly Steve Wilkinson]

Well, as a previous poster said, he bought a used one--I now realize he must have been talking about the relay that I wasn't aware of--for $20, swapped it out and everything worked fine.

Stephan

[steve911]

Charly--
The seat belt buzzer relay is behind the instrument cluster (I think behind the speed) - its black and rectangular. Most of the time, folks want to remove the annoying bugger, so they put the key in the ignition, open the door and find the offending buzzer (there are a couple of relays in close proximity). Don't know what to tell you if yours is not working - could be that the PO already removed it

Mine is in the glove box (I think - I'll try and find it to get a part #)

[Shipibo]

Thanks Steve.

[cary]

Its behind the oil gauge.

The board in the seat belt has a logic circuit on it.
Do a search. Some time ago Warren gave a schematic of the little logic board.

[Shipibo]

Thank You, Cary. Will try to locate. Charlie

[Superman]

Resurrecting this ancient thread with some questions. I have two of these units, which I have plugged in using no less than four sets of lamps, and the lights do not come on. At least, they do not come on when I turn the key to "run," while sitting in the driver's seat with the handbrake on. The seats, seat belts and brake pads in this car, and every other SC I have owned, do not have electrical connectors.

1) When do these lights come on and go off? Seat belt light comes on and then goes offer after X seconds? Seat belt light stays on until the seat belt is fastened? Brake light comes on when the park brake is engaged? When should these lights come on and go off?

2) It appears the system which operates these two warning lights has been disabled. Again, four pairs of lamps were used to test this system, and none of those eight bulbs emitted photons. How do you suppose this system was disabled?

[Superman]

Okay, here is a simple question: Does either the Brake or Seat Belt light come on when you first turn the key to "On?"

[FrankM_]

This is the schema for a 84-86 Carrera, on the SC I believe there is one less warning light ?

Anyways on my MY85 the 'Kombikontrollleuchte' work as follows :

- the 'relay' (schema: 'Schaltgerät für sicherheitsgurt') is behind the 2nd gauge from the left and it is triggered by a seat belt contact switch, even on the 82 SC schematic (2nd schema). The text on the left also indicates the bridging of this socket for ROW cars ( 'Brücke' = bridge )

- the brake pad lights are just one continuous circuit through the 4 wear indicators and the light should only come on when the circuit is interrupted I believe (to be tested), they don't come on when I turn the ignition contact on (pin 1 and 2)

- the parking break light comes on when the ignition is on and the parking brake is pulled up (pin 4 gets ground through the 'Handbremskontakt'

- the 'buzzer' sounds when the contact is on (key turned) and the door is open. It is not a buzzer actually but the relay constantly cutting its own power and turning itself on/off that makes the sound

- my seatbelt light lights also when the belt is not in after turning the key in the contact, but it shuts off after some time even when I do not plug in the belt (probably driven by the capacitor charging in the electronic part of the 'relay' ? Pin 6 provides the GND for the lamp through the diode and the lower transistor when it is conducting)

- pin 3 of the light fitting = power, pin 5 looks like the GND
pin 7 from the oil pressure switch (probably to indicate engine on / off)