Handbrake switch wiring series III


(Weston Keyes) #1

Hello Folks,
I think this circuit is the same on a series I and II as well?
My brake warning light was burned out so I replaced it. It was off and working fine with the brake reservoir float level switches. When I operated the hand brake the light would not come on so I got into where the switch was and tested the switch. The brake switch is working fine but I have no voltage at the black and white wire that feeds it. Also the brake light is always on despite removing the wires from the reservoirs. So in playing around by the switch I must have grounded the circuit?? I can run a new wire to the switch but I can’t get the light to go out. I have a wiring diagram but it doesn’t tell me where the black and white wire actually connects in the dash. Any hints, clues?

Many thanks
Wes Keyes
York, Maine


(Ole Würtz) #2

The S3 has a brake circuit fail switch that will cause the brake indicator light to come on like the reservoir switches and the hand brake switch.
It is located under the heater blower kind of next to the second brake fluid reservoir.
Simply disconnecting should make the light go off. If that is the reason.
Good luck… Ole


(Weston Keyes) #3

Ole,
Thanks. You are right on. As soon as I disconnected the single wire going to the brake failure switch the red brake warning light went out. I recently replaced both the master cylinder and booster and bleed the brakes. The pedal is rock hard so I assume there is no air trapped anywhere. I am getting 12 volts going to the switch from the harness. I put an ohm meter to both pins of the switch and it shows each are grounded. Without any pressure in the brake system I would assume that this switch should not be grounded? Does anyone know if there is a test I can perform on the switch to prove it is good or bad? It looks like it is a fairy pricey part to replace. Many thanks.

Wes Keyes
York, Maine


(Weston Keyes) #4

Ole,
One of the vendors sells the plastic switch separately so I may replace that and see if that fixes the problem.

Wes Keyes
York, Maine


(angelw) #5

Hello Wes,
If the Pressure Differential Warning Actuator has operated, both pins will have a path to Ground (the switch is made). If you use the ohm meter across the pins, you will have continuance. You need to reset the switch. The procedure is set out in the S3 Workshop Manual.

If you don’t have a manual, send me a message and I’ll scan the pages for you.

Regards,

Bill


(Weston Keyes) #6

HI Bill,
Thanks so much for the help. I didn’t realize that switch could be reset! I have a CD of both the Parts and Service manual but the computer that can access those files is down right now and my Chrome book is useless for that purpose. If you could scan them or email them to me I would be most grateful.

Wes Keyes
York, Maine