ABS light on

[madrone]

I have an Oshkosh four wheel steering chassis produced at Gaffney shortly before the facility was sold to Freightliner in 1995.

http://www.rvtechstop.com/articles/allsteer.pdf

It has full air brakes and an early ABS system. I recently had new tires installed and evidently the air wrenches shook something up and ever since my ABS light has been on. If any owners of the early air brake FCCC
pusher chassis have had similar problems I could use any information
you have. Oshkosh did not pass the AllSteer system on to FCCC but in
most other aspects the early chassis retained the Oshkosh design and parts remained the same for some time.

Thanks in advance

[MonacoMama]

Does anyone have any ideas on how to help madrone with his ABS problem ?

[MuckSavage]

Not direct help, but I get an intermittent ABS light. I'm told it's from dirt fouling the sensor. It clears itself up rather quickly.

[WilleyB]

Well I've been through the Ford system, but I have no idea of how his is setup, so with that in mind
1 Check the voltage of the ABS sensors, they should put out 0.7 volts (700 milli volts)with the wheel turning. I don't know what the minimum output is but I suspect it would be around 0.3 volts (300 milli volts)
(a) To check this you need a Digital voltmeter with a 0 to 1 volt range
disconnect the ABS sensor and insert the probes of the voltmeter than spin the wheel.
( I used a "C" clamp to compress the caliper piston a bit to release the brake pad drag
on the rotor) That will check out the sensor. A low reading on the voltmeter will indicate a dirty or defective sensor. Clean and retest and if necessary replace sensor.

Without knowing anything about the chassis there's not too much I can say.
For example on the Ford the ABS light will come on if
(1) the brake fluid is low in the reservoir (2) Defective or Dirty wheel sensor or broken wire (3) Air in the brake lines or any hydraulic brake malfunction (4) Dirty or malfunctioning speed sensor on the rear differential
So your chassis may be similar or could be quite different, in any case start checking the wheel sensors.
NOTE: on the rotor there is a toothed ring, as the teeth pass the sensor a voltage signal is generated and passed to the electronics system. If the ring is damaged or the sensor alignment is not correct the signal will be affected.
Afraid that's about all I can come up with.

Cheers
Willey

[Wayne M]

As Willey stated:

It may be just dirt. Try a water hose with a pressure nozzle and spray up and around the wheels. (No worse than driving down the road in a heavy rain) Worked for me some time ago.