HI everyone.

My ABS light has been on on a new (old 93) Aerostar I am getting ready for the family.

I have read and found what I could on the sytem and have done all the following;

- purged all old fluid(really dirty) with new brake fluid. ABS light still on

-Checked reservoir switch and pressure diff switch OK, Red brake light on when I pushed float down and when I jumpered the diff switch.

-I dissconnected the RABS valve, ABS light on, Red light on when I press the brake(engine not running, key on)

-I pulled the diff mag pickup, looks good, coil checks?

I have not pulled the codes yet, but will do tonight. Any ideas??

on a working ABS system, will the light go out if you turn the key onand not running, or does the engine have to be running to get the light out, just to help me troubleshoot(dont have to start all the time)

Thanks everyone!!

 

When you pull the codes, you'll likely get an 03 or 04, isolation or dump valve problem in the RABS unit. Since your old fluid was really dirty, there is a high probability there is corrosion present in the RABS valve unit, around those valve seats. When you disturb them by flushing or activating the RABS system, the valves do not reseat correctly and give the error code. My experience with using both Ford and Chilton diagnostic manuals, has been less than satisfactory when troubleshooting RABS problems, so be careful when trying to interpret those codes with the help of a manual.

At this point, there are several approaches you can take.
1.) Outright replacement of the RABS valve unit with a rebuilt one. Cost runs around $100-150 for a rebuilt one.
2.) Try tapping the RABS unit lightly, several times, with a rubber/wooden mallet to see if you can get the valves to re-seat. I've never had any luch with this method, but theoretically, it is supposed to work. This is the eternal optomist approach.
3.) Do nothing. Sometimes these problems 'cure' themselves over time. While the RABS light is on, the anti-lock system is bypassed, but you still normal braking to the rear wheels, just as cars/vans have had for years before RABS was an option.

If memory serves, the yellow ABS light should wink out after an internal system check is satisfactory, with the key in the ON position. Just to add salt to the wound, be aware the RABS system is inoperative at speeds below 25mph. so, some other problems don't manifest themselves at idle.

Best of luck in sorting this out.