pressure switch? (abs)

Chicago SC

Registered User
What the F.......pressure switch? (abs)

I recently read Duffy Floyd's ABS system article and it was very helpful to diagnose my problem with no power brakes...However, now I'm stuck. The problem is that the Hyd. pump motor wont run when starting the car. The pump motor relay clicks when tested, and I do have power from the relay to the pump motor connector, but when the connecter is on, the pump wont run... BUT, I hotwired the pump motor by connecting a negative pin on the pump motor plug to my battery and it turned on. Now that I know the pump runs and i have power brakes, what could be stopping the pump from turning on by itself when it is hooked up? By the way, the pump also would not shut off on it's own when I hotwired it...Is it the pressure switch???????????
 
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So you are saying when there is power to the terminals of the motor the pump will not run, but when you hotwire it runs?

If this is the case, it sounds like a wiring issue. Did you ground it when you hotwired it, or use the ground from the factory wiring? Perhaps the ground is bad..
 
we grounded it to the engine compartment. Also, when we used a positive pin on the plug to try and hotwire it , it wouldnt work. only the neg. pin would.
 
its not the ground. what the hell is goin on here? this whole abs system is nuts!!!!! I Need my power brakes back!! I have a hunch it may be pressure switch but i dont know exactly. how do i find out?
 
Duffy personally helped me out diagnosing my ABS problem...i have all the diagrams of what i tested and all other stuff at home I'll check them out when I get there. Mine turned out to be the presure switch but I also went step by step testing everything from the pump, to the relays, to the press. switch. That article is BASIC to understanding the teves mark II system, and yeah..ikt still sux. I was glad i got my name inthere as collaborator! (I was the formerly known as SC KIDO...when i was like 16 or 17)
 
Been here, done this...
Assuming your car is the early model with the Teves Mark II ABS System.......If you look on Duffy's abs article, you want to find the diagram that shows how to ground the #4? pin connector on the Pressure Switch electical connector (Not on the switch itself, but the wire harness going to it). If you do this, AND the pump runs, then the pressure switch is bad and not the relay because the Pressure Switch tells the relay when to turn on power to the pump. Don't buy a pressure switch from Ford as:
A) Too expensive...
B) No longer available.

From a previous post.......
"GM Part #25530882 "Pressure Switch" (May not show up on "Part # Search) Think they are $84.00 now from http://www.buy-gm-parts.com/
Shipping will run $12 - $25 depending on how fast you want it.

Click on "OEM Catalog" choose "1988 Buick REATTA" and then in the Brakes" section choose "Anti Lock" then "Pressure Switch". OR just email them the part number direct. They shipped it out in two days to me, just UPS took forever.
Email: parts@crowncadillacolds.com OR call Keith at 1-888-337-1094 ext-1127

They may ask for a VIN #, so calling them might work better. Keith will understand if you talk to him and tell him it's for the 89-93 Ford Supercoupe w/ same brake system as the 88 Buick Reatta w/ ABS. Mine has been in and no leaks for two months. Works good!"

Hope that helps....
 
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