EnBee

What is normal behavior for the ABS warning light on startup for a 1985-1986 car? In my car, when I move the key to the run/ignition position without cranking, the antilock warning light flickers twice then goes off. All the other warning lights stay illuminated and then go out when the engine starts. Longer explanation below...

------------------
So I'm in the process of trying to resurrect the ABS on my 1986.0 US 5-speed. The previously owner had thoughtfully dealt with the problem of a persistent ABS warning light by removing and tossing the bulbs for the "!" symbol and the antilock light. So much more sophisticated than just putting black electrical tape on the dash pod...

At any rate, I've checked out my wheel speed sensors with a multimeter and found two bad ones (one front with resistance way too high, one rear with open circuit inside the sensor). I managed to find replacement Bosch sensors from a couple of other cars that fit, at least in terms of overall diameter, mounting point, and clearance to the reluctor ring on the hub. [If I get the system working properly, I will post details for the other early ABS owners out there who suffer the heartbreak of NLA-itis when it comes to sourcing replacement wheel speed sensors.]

So now I am stuck trying to figure out what else might be wrong. Sensor resistance is within spec for all four wheels when measured at the connector for the antilock control unit in the driver side footwell, and none of the leads are shorted to ground. I still get the "!" and antilock warnings after driving a short while, which I believe indicates that the system is failing the sensor check. My next step will be to get the car off the ground again and spin the wheels individually to check that the sensors are putting out appropriate voltage (the ABS manual sez around 2V AC at 1 wheel rev/sec), but first I want to see what the behavior of the antilock light is supposed to be at startup before I go barking up the wrong tree. It would make sense for it to act like the other lights (stays on during bulb check with key in run position before starting, goes off after engine starts), but AFAIK it might be behaving as expected...

Thanks!

NB

davek9

The Anti-Lock on the three I have comes on w/ all other warnings lights and stays on until the engine is started, then they all goes out w/ exception of the "brake light" until the peddled is pressed.

It is my understanding if the Light comes on with engine running (started) and you have yet to move the car it is a bad Relay.

Once the car moves if the light comes on a wheel sensor is bad or the connection is faulty.

When assisting a friend (AO) w/ his, we used a scope at the brains connector and spun each wheel and saw a plus on all but one, it turned out to be a bad under hood connection.
Note: we also noticed that the signal strength (peak to peak) was not the same for all wheels but that did not seem to matter for it to work.

Hope that helps,

Dave

EnBee

Very helpful! Thank you. I suspected it wasn't normal behavior...

Looks like I have two problems to chase down... I will start by spinning the wheels and verifying signal; if that passes, I will have to do some more digging.

Thanks again!