Brake Problem

#1

Guys got an 89. ABS was not working. Swapped out ABS brain, and both relays on top of pump. Checked wires, ok, Changed the relay inside the car tonight and ABS light goes out. Go to test drive vmw. Drive about 50 feet light comes back on. Restarted car while moving ABS works, tested and car pulls to the left when ABS is actived. Seriously to the left, like the other lane- Really Bad. Turn car off, restart go above 1k rpm ABS light comes on.
When ABS is not working rear pass side tire locks up but car does NOT pull to the left. Bentley tells me it’s the proportioning valve. That causes rears to lock up and car to pull to side when braking. That one seems easy.

The ABS light turning off. Sounds like a short somewhere? How would you go about tracing a short? Any other ideas?

#2

Find out where the sensor wires come into the harness connector at the ABS brain. Test to see if there is continuity on each of the sensors. If not, there is a break on that sensor wire. This could be a source of the problem.

#3

Check the wiring from the speed sensor connectors to the sensors and check the sensors themselves. A simple resistance check may point out a bad sensor.

It wouldn’t be a bad idea to pull each sensor and blow off accumulated metallic grunge from the sensor and the thoothed wheel.