ABS Light

bytor

Well-Known Member
Hey Grumpy, working on a few minor issues with my ‘new to me’ 87 Corvette. The ABS light stays on all the time and I have determined I have a bad ABS module relay. The relay coil is open. This is a special "over-voltage protection (OVP) relay" which controls power to the ABS control module. It has a few diodes built into the relay that you don’t typically have with a normal relay.



The relay part number is (PN 1636973) and it would seem to have been discontinued some time ago. Any ideas on where I could get a new replacement relay? I can get a used one off ebay I suppose or Frankenstein the existing one by replacing the relay part while keeping the diodes intact.
 

Attachments

  • Drawing1.jpg
    Drawing1.jpg
    87.7 KB · Views: 28
  • DSC00697.jpg
    DSC00697.jpg
    5.7 KB · Views: 28
  • DSC00699.jpg
    DSC00699.jpg
    6.3 KB · Views: 28
heres a link and some related info that might prove useful
THESE GUYS CAN AT TIMES SUPPLY GOOD USED PARTS
http://www.vette2vette.com/parts-request

http://www.corvettefever.com/howto/19239/

http://www.absfixer.com/

http://www.absfixer.com/catalog/product ... lqiflrutd2

http://www.vetteweb.com/tech/vemp_0403_ ... ewall.html

absz1.png


absz2.png


The most common problem with the ABS system is this relay (PN 1636973). There are several tests you can do to check whether it’s working properly. The pins have numbers to identify them, and we’ll be referring to these numbers and the corresponding wire colors to do the troubleshooting.
If you get the dreaded ABS light, first check the fuses. There will be a 10-amp brake fuse and a 10-amp fuse for the gauges. If they’re OK, proceed to the modulator assembly. Since our car was a convertible, we had to remove the speaker assembly to get to the module.
To check this relay, turn on the key and use a test light to make sure there is voltage at pin numbers 15 (pink/black wire), 30 (orange/black wire), and 87 (orange wire). If there is voltage at each of these connections, the relay is working properly.
If the relay has no voltage, check the connector that leads to the relay to make sure it has a good connection.
Also check the ground on this relay by testing pin number 31 (black wire) for voltage. This is the ground for the relay, so there should be no voltage. If the test light illuminates, you have a bad ground on this wire. Check the ground connection further down the wire (shown) to see if it has proper contact. If the test light illuminates on both sides of the connector, your ground problem is further down the line.
If the module relay checks out, this relay will be the next to check. There are two of them. One operates the pump motor, and the other operates the solenoid. Both relays are located on top of the pump. Because they connect directly to the top of the pump, check these relays by simply exchanging each with a new relay.
Also check the ground on this relay by testing pin number 31 (black wire) for voltage. This is the ground for the relay, so there should be no voltage. If the test light illuminates, you have a bad ground on this wire. Check the ground connection further down the wire (shown) to see if it has proper contact. If the test light illuminates on both sides of the connector, your ground problem is further down the line.
If the module relay checks out, this relay will be the next to check. There are two of them. One operates the pump motor, and the other operates the solenoid. Both relays are located on top of the pump. Because they connect directly to the top of the pump, check these relays by simply exchanging each with a new relay.Or you could remove the control module connector and check pin position 9 for voltage after the relay.
If you run all of these tests and still haven’t found the problem, check the high-amperage circuit to see if it has power.

ABS brakes are a complex but valuable asset to the Corvette driver. As with many complex systems, they require some attention from time to time. The system is designed to give the driver notice that it's working properly. A whirring sound accompanied by a pulsation of the brake pedal are typical signs that the system is working as it should. If these events aren't noticed, there's a systematic solution to troubleshooting the ABS that can be done in the driveway by the most novice of mechanics. Follow along as we diagnose ABS.

If you have an intermittent problem with your ABS, check your module relay by tapping it to see if it's sticking. As complex as this system is, Chris Petris reports that he has had to replace only one module in all his years of working on Corvettes. He says the reason for the failure is the car was repeatedly jump-started, and he believes the cables may have been crossed at some time. With that in mind, these tests should identify any problem you'd typically find with your ABS brakes.

Considering that the purchase price of a test light and the necessary relays is cheaper than the cost of a technician to find the problem, it makes perfect sense to arm yourself with this information and strengthen your wallet, as well as your ABS.
 
There used to be a couple of Ebay sellers that specialised in C4 NOS Parts Bytor.
I haven't looked in some time now. Back on the Pontiac bandwagon for 2014.
Those guys in past seemed to have everything.
 
Just a FYI. After getting my 86 from winter storage, after the first short run or two, the ABS light came on. Yesterday the SES light came on also in addition to the ABS light. Well I don't have a battery tender at this time, but I'd read if the battery was down or the alternator had a problem, this pair may come one. Got out my battery charger and put it on trickle last night. Took it out today and both lights are out and I think I can hear it do the self test. Someone had posted this info where I'd read it and I was skeptical but sure seems to be valid. Fairly sure it must have been the battery was down because it's showing 14.1 volts when running.
Just FYI in case someone else comes up against this and a possible solution. It worked for me.
 
Hey Grumpy, working on a few minor issues with my ‘new to me’ 87 Corvette. The ABS light stays on all the time and I have determined I have a bad ABS module relay. The relay coil is open. This is a special "over-voltage protection (OVP) relay" which controls power to the ABS control module. It has a few diodes built into the relay that you don’t typically have with a normal relay.



The relay part number is (PN 1636973) and it would seem to have been discontinued some time ago. Any ideas on where I could get a new replacement relay? I can get a used one off ebay I suppose or Frankenstein the existing one by replacing the relay part while keeping the diodes intact.

I'm having the same problem. Where you ever able to find the part for replacement?
Thanks
 
I got mine used from these guys. http://stores.ebay.com/FParts But check around with other Corvette used parts dealers.
I have had no issues with the ABS since I installed it.

Send them a note and see if they have any.... Good folks to deal with.
 
Back
Top