SaabCentral Forums banner

Brake Lights Not working, ECU? ABS?

6K views 7 replies 6 participants last post by  yaofeng 
#1 ·
Ok i'm totally new to the Saab club, Before I was a die hard rotary man with years of RX7 history, modifications and engine rebuilds :confused: But the Saab offers 4 seats, lots of torque and less frequent trips to the petrol station.

But I bought a banger of a 1990 Saab 9000 Carlsson, which I'm trying to first get road worthy then slowly bring it back to its former glory.

the biggest problem I face is no brake lights:( , checked all the stupid stuff already, then checked switch and wiring to the the back, all of which ws fine. Therefore I'm worried its the ECU or ABS computor if it has such a thing. I believe that with ABS it takes a signal from the brake pedal to know when braking is occuring.

To be honest I'm shooting in the dark, I dont have a clue!! If it was a RX7 I'd have the ABS fully removed by now anyway:D (it was no good for drifting)
 
#3 ·
Yeah I have checked the bulbs, I've had the switch out and checked it. Also Car has been to an auto-electrican who cant figure it out.

Obvoiusly not a good situation, I'm thinking of just wiring up the lights to work off the switch. Very worried that doing this puts the ABS out the loop but the hydraulic module (ABS pump) is still fitted.

All the other stuff wrong with the car is easy fix, but this has me head scratching.
 
#4 · (Edited)
The ABS computer will have no impact upon the brake lights working or not working in a Saab 9000. If this was the case they would not work if the car was off (key off) and the brake pedal was depressed.

Have you checked the lamp filament monitor on the main relay panel underneath the dash? Have you double checked the all of the fuses for the brake and tail lights? Have all the grounds (earthing points) for the brake and tail lights been checked? Have you tried to bypass the switch - jumper it to see if the brake lights light up then?

You either have a bad brake light switch, fouled ground(s), an open wire(s), a bad lamp filament monitor, blown fuses, or bad lamp holder boards for the tail lights. The ABS computer is not electrically connected to the brake light circuit at all.
 
#7 ·
You may have solved you problem already. I had two 9000's with the same problem turned out to be the wiring harness that goes into the trunk on the left side. Inside the wiring bundle the casings on some of the wires may have cracked and are making contact. This can cause all kinds of weird issues. On my 1990 all the lights on the right side of the car would not come on. In my 92 the car would stall and sputter and many other random things happened. Check out the harness it can save you a lot of expense. Good luck.
 
#8 ·
Make sure you remove the correct switch located near the hinge of the brake pedal farther in and up and not the switch for the cruise control just above the knee bolster.

The brake light circuit is dead simple. It is always hot. You should get 12 volts at the switch.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top