ABS unit - 1988 corvette

my mechanic tells me that the ABS unit on my 88 is probably shot -- left front wheel will lock up on hitting the brakes -- we've already fried one set of calipers trying to figure this out.
Initial attempts at finding this unit have not been successful -- apparently GM views this to be obsolete; from what i know this particular version of the system was used 86 thru 89.
Any suggestion out there as to where we might find a unit? or anyone know of anyone who repairs these?
alternatively, anyone know of any methods to bypass the ABS and just rely on normal braking.
without this, the car is not operational
thanks for any help
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snipped-for-privacy@sei.cmu.edu wrote:

Sounds like three problems. 1. The self-test in the ABS isn't working and is leaving a defective unit on line without a warning light. (Blown fuse?) 3. You need someone experienced in Bosch ABS working the job.
This unit has three channels (left front, right front and rear.) It works by intermittently releasing pressure from a caliper, not adding it. As such, it should fail-safe and/or show a warning light. Trapping pressure in a single caliper line seems weird.
Section 8 (electrical) in the Shop manual has a troubleshooting routine with a number of tests that can be done using simple test gear and a "come-out" box that connects between the Chevy and Bosch wiring. There is also a test unit made by Bosch that tests the whole system. The Bosch ABS was also used on a number of cars in the late-80s -- my cousin's Chrysler New Yorker had what looked like the same unit as my C4.
If the parking brake is working, get the car rolling at 5-8 mph and note whether the ABS goes through its self-test (pump runs for a couple of seconds then stops) and whether it throws a warning light when it does this. Then, stop the car with the parking brake. Mention your results when you find a brake guy who can fix ABS. Meanwhile, open the Bosch connectors and look for corrosion or oxidation on the copper contacts (this was a typical Bosch problem). Check the fuses and check for power in the lead that goes to the ABS unit.
A Chevy dealer might provide the name of a outsource shop where they farm out work on C4 ABS. If not, suggest calling large, independent brake shops in your area (Pitt, PA?) and look for someone who services Bosch ABS and has a Bosch ABS test set (same as GM J35890). It may be helpful for the brake shop to have the electrical section of the Corvette shop manual. It shows how the Bosch wiring interfaces with the Corvette wiring harness.
A quick Google showed that there are still wheel speed sensors available as well as rebuilt ABS pumps and control-modulators. My own preference would be to repair the system rather than try to "plumb" around it. Plumbing around the ABS control modulator might involve some proportioning between the front and rear brakes--not something I'd play with on an "instant engineering" basis.
--
PJ
89 HookerCar, 02 E-blu 6-spd Coupe
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"EVERYTHING" pj said is good advice greg

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