Early Kelsey Hayes ABS controller mystery

Early Kelsey Hayes ABS controller mystery

Postby pozo izquierdo [OP] » June 22nd 2020, 8:55pm

Hi all, I earlier asked about possible service locations of early model KH ABS controllers. Well, I decided to take a peek in the unit before starting to send it anywhere. Now this unit was originally installed in my 1992 AWD Astro by local GM dealer back in 2000 or so and it worked until 2010 when it was replaced by a third unit that is currently in place and I have the red and yellow brake alarm lights on.
This unit #2 was removed at my presence ten years ago and I simply stored it in my warm and dry garage and kept it as a spare for future remanufacturing.
Well, today I took a closer look at it. It has a sticker on the top that says "This unit is not dealer serviceable, do not tamper with the assembly fasteners". Why there were only three screws left that were holding the upper control box in place? As the first picture shows, some of the screws have been taken out with help of a grinder. Unfortunately I will no longer get answers from the GM dealer who charged me 3000 USD for changing the first ABS unit to this one about 20 years ago. If the unit was properly remanufactured as the sticker says, who had left it in that kind of shape? I guess that remains a mystery and I will not get anybody accountable for that anyway.
Soooo, I opened the remaining three screws and inside the cover there seems to be a circuit board that looks like new. This board seems to be full of small and delicate components that I don't want to fiddle with any hot soldering iron.
This circuit board is connected through a quite heavy looking 17-pin connector to the lower part of the ABS unit. There is a rubber isolation in between the upper and lower part and the pins come through it.
Underneath this rubber there seems to be heavier electronics and also familiar looking soldering points from various Youtube videos that show the fixing of newer model KH units.
But then I took a look at the 12 V pump motor that sits underneath the unit. There is a clear pair of cables leading to the motor so decided to simply disconnect the connector from the circuit board and give it direct 12 volts and see what happens.
Nothing happened except sparks on my battery terminal.
Then I decided to open the motor and voilá! The damn thing was all rusted and did not move at all! With help of WD 40 and and a lot of patient turning back and forth I finally got the front bearing loose and was able to turn the collector. On the tip of the motor shaft there is a small eccentric and there seems to a be a needle bearing on top of that. The eccentric turns in a round hole and in the hole there two shaft ends that obviously move in and out when the eccentric pushes them. This must create the pump action...These shaft end have some rust as well and don't seem to move.
Anyway, I gave a quick cleanup to the motor and put it back together and new test. It ran! (with terrible noise of course) Well, at least the copper wires in the motor are ok. Now that I know the motor is not totally dead I will try to clean it properly and hopefully get the needle bearing turning as well.
Now thinking back, perhaps the original fault code of this unit came because of the moisture in the pump motor. Then a new unit was put in and the old unit was never paid any more attention. The moisture was left in the motor and during 10 years sitting in garage it did a thorough job. I'm just hoping that the moisture in the motor did not burn something from the circuit board(s) which will be impossible for me to fix. If the only problem was the pup motor, then that I think I can fix.

Currently I am at my summer cottage away from the ABS unit and I PM:d "doogaloo" of this forum as he kindly offered his assistance as he has worked at Kelsey Hayes. If there is anybody else who has worked on these early KH 12280800 (or whatever the actual model is) units it would be nice to hear their experience.
I still have the unit #3 in my Astro and when I took a look at it at least it seems to have all the top screws in place but removing it is not as easy as in the newer models. Or at least it looks like I need to disconnect a bunch of brake lines in order to get it out. But at least I have two units to play with and with some luck I hopefully can get one that is working properly.


Ari Ignatius
Hyvinkää, Finland
This shows two of the total of five missing screws.
There is a circuit board inside the cover. Looks like new...
The rubber isolation between the upper and lower sections is removed and underneath it looks like this. Heavier electronics and soldering points.
This shows the motor and the cables to it.
This is what the motor looked inside. The collector did not turn as the bearing was all rusted.
This is the end of the motor shaft with small eccentric and - as it looks- a small needle bearing that is pushing the shaft ends in the pump cavity. The cavity and one of the shaft ends is seen on the left.
Ari Ignatius
Hyvinkää, Finland
1992 Chevy Astro AWD Ext, 1:st owner
Original Poster [OP]
pozo izquierdo
Fueling (Empty tank)
Fueling (Empty tank)
Posts: 7
Topics: 5
Joined: June 2020
Location: Hyvinkää, Finland
Gender: Male
Alias (AKA):
Van Model Year: 1992
Van Make/Model: Chevrolet Astro
Extra Info: AWD LT Ext

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