The shuttle valve switch should just unscrew from the MC/combo valve. There should be no brake fluid in its hole. If so, there is an internal leak, and the valve needs service or replacement. Moisture can get into the hole, since the switch does not provide a waterproof seal.

 

My RABS light came on a couple weeks ago so the first thing I did was a search on this board for "Rear ABS" and found this topic. After reading down through it, I saw the simplest thing to do was pull the connector off the master cylinder and clean it. I did and put a little dielectric grease on it before plugging it back in. It worked! The light's out now! Thanks for all who contributed to this topic!

 

I got so tired of checking and checking that I just pulled the dammed bulb out.

 

I got my Aero fix tonight by reading this entire thread. Great stuff here.

 

great! come fix mine!

 

While the RABS light is out, I've never felt the brakes pulse on this van the way it did on some of the others I've owned. I'd like to get that working again but it sounds like a lot of work and very costly to overhaul or replace the valve that does that work.

 

The brake pulses you felt were probably from the warped rotors. It's a common problem with the insufficient brakes on these vans.

 

I've changed an inordinate number of rotors down through the years, rest assured I know what hard spots on the front rotors feel like.

If your RABS is working correctly, you won't be able to lock-up the rear tires. The RABS should since the wheel lock-up and begin pulsing the rear brakes to allow the tires to keep turning and keep you in control. If you've never felt that happen (on slick roads), then your RABS isn't working - like mine.

 

I'll have to say that I've never felt that ABS pulse on my van, so maybe mine isn't working. I once had to jam on the brakes in the snow, and all tires stopped spinning, but the van just kept moving, sliding on the locked tires. Don't know if that was a good test.

 

That was as good a test as can be done. If it was working, the rear tires wouldn't have stopped turning completely. When the ABS kicks in, you can not only feel it but also hear it ticking very rapidly.

I think the valve that does the pulsing is prone to corrosion and sticking. I'm not sure but I think it's called a combination valve. I may have to find out about replacing it some day. From what I've read, it's about $160 at Autozone.

Check this post over at the other Aerostar forum:
How To: Solve ABS problems on a 1995 Aerostar. | Ford Explorer and Ford Ranger Forums - Serious Explorations See reply #15.

Here's the listing for it at Autozone:
https://www.autozone.com/brakes-and-...unit/47565_0_0