90 abs pressure switch

i spoke with prior (russ), they really don't sell the abs pressure switch outright. he said he could order it, but would have to mark it up. he suggested that i go directly to the local dealer. the local ford dealer told me earlier that it was "discontinued". so after speaking with prior, i went to the mercury dealer and they gave me the part number (E7SZ-2C244-A pressure warning switch kit). it list for 150.00. (ouch). also contacted five star ford in az., same price, but he sells for less that list (125.00). DOES ANYONE KNOW OF A AFTER MARKET MANUFACTURE?
i thought i read an earlier trouble shooting post that suggested, the abs relay and pressure switch as a cheaper way to go.
i've replace the abs relay, and it still has the abs light "on" and the brakes are very hard. the pump doesn't run when you turn the key "on". if you put 12 volts directly to the pump, then the pump can be heard. does that sound like the switch?

Yes. It does. You can check one further thing and that is measure the resistances of the switch itself, and jumper the switch plug to see if the relay engages. That will confirm it for you. If you don't have a wiring diagram, or you don't have access to the TBSCEC article by Duffy, I can tell you which pins to test later.

As far as availability, you could also consider getting a used switch from a junk yard.

90 abs question

tbirdscfan, is that pin 4 of the pressure switch connector to ground? that powers the pump motor relay and then the pump?
thanks, bob

Yes. Pin 4 (pink/lite-blue wire) to ground with key on should start the pump running. Thats what the pressure switch would do.
Also, with the key off, press brake pedal about 10 times, then measure the resistance from pin 1 (grey wire) to pin 4. It should be 0. If it isn't 0, the pressure switch is definitely the culprit.

is that pin 1 and 4 of the pressure switch itself, not the connector? and it should be zero ohms?

That's correct. The pins on the switch itself. To jumper the pump relay, however, you short the pins on the connector.

By pressing the brake pedal repeatedly, you are releasing the pressure until it falls below the point where the pump would normally kick in. At that point, the circuit from pin 1-4 of the pressure switch is closed and should read 0 Ohms. If it were plugged in and working properly, that would cause the relay to trip and the pump to run until it reached operating pressure at which time the switch would open and cut the relay out..

I purchased a brake pressure switch for $85 about three months ago from my local Ford Dealer. They printed out a diagram on the abs system that gave the part number and we ordered off of that. I can try to find the receipt for the part number if you still need it.

Just post and I will try to find it.

Bob

bob, thanks for the offer, but i have the part number in the orginal post.
tbirdscfan, thanks for all your help on this. i found a pressure switch today at the local "pick and pull" junkyard. it ohmed out ok on pins 1 and 4. i'll check mine in the morning and then replace it if needed. i'am not looking foward to removing the abs unit again. the book says you can remove the switch from the bottom if you have the special socket. i couldn't find one, so i'am using a 36 mm axle nut deep socket. the socket wall is too thick to clear the electric pump. so i'll be removing the abs assembly and then the electric pump to get to the pressure switch. i'll let you know how things come out tomorrow. bob

tbirdscfan, everything was going good, then i moved the car, now same problem and one additional problem, brake light on.
started this morning with grounding pin 4, pump ran. removed abs unit, ohmed out pins 1 and 4 of the pressure switch, was open. removed pressure switch. found the pressure switch's center metal rod retracted inside of the switch (wasn't like that when i installed it before, it was sticking out about 1/16 inch when installed). replaced pressure switch and reinstalled the abs unit. turned key to "on" pump was running. tried it two more times, pump still ran, brake pedal felt NORMAL (like power brakes), but abs light still on. top off brake fluid and bled the brakes per the manual. brake pedal felt normal and the abs light was off. i pumped the brakes several times, still felt normal and no abs light. started to rolled down the driveway for a test drive, hit the brakes, both abs and emergency brake light now on and the brake are very hard like before. after a LONG BREAK! depressed brake pedal 20 times with key off, tried grounding pin 4 of the pressure switch connector (key on), pump not running. put all tools away for the night. will try again in the morning.

Interesting. With the latest problems you're describing, the ABS pump relay sounds like the problem. That is when you grounded pin 4 of the connector (on the wire bundle) with the key on, then that SHOULD start the pump running. If that's not happening now, the places to look are: the relay (brown relay on the passengerside firewall up by the EEC test plug) if it hasn't ever been replaced; the wiring at/around the ABS unit to see if something got pinched or torn or isn't fully plugged in; the fusible links. The fusible links are hung off of the starter relay, the wire is Tan/Yellow-stripe. You can test for power at the relay base itself if you don't want to dig around for the fusible link. It is pin 4 of the relay base.. it is always hot (12V) even with the key off. Pin 2 on the relay base, is hot whenever the key is on. There appears to be a fuse which runs to pin 2 of the relay.

Since that fuse is switched, look in the fuse panel under the dash on the driverside to see if any are blown.

So, I'd check fuses first, test voltages next, replace relay last. We just sort of have to assume your pump is working, just not getting juice.

Hope this helps.

relay going bad

I didnt have the problems your experiencing but if the relay is bad your accumulator is prolly bad also hence causing the relay to switch on and off, on and off, if it sounded like a slower turn signal relay from behind your glovebox then relay and accumulator need changing I have worked over the brakes three times on mine and taking off the accumulator makes it easier to remove the whole assembly if that is what your doing. hope this helps brakes on these are all related around that accumulator if it is bad it will give everything else problems 2