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Well, I've driven the Aero a few times and the Rear ABS idiot light is "OFF"!!! Hooray!!! The light bulb seems to have been the issue. Thank you to everyone for all of your help!!
Now we are on to working on figuring out what is making a hard "Thump/Clunk" from the front end AND what is going on with my front brakes making a terrible grinding noise. Ahhhh... gotta love owning Fords.... (fix or repair daily )
The Cowgirl Mechanic
Driving the Aero.....and Lovin' It!!
1994 Aerostar EXT E4WD w/ tow package 135K & counting...
1. worn out upper/lower ball joints or control arm bushings
2. worn out half shaft joints
3. defective AWD shaft speed sensor (2 of these gremlins) on top of transfer case or sensor wiring
front brakes making a terrible grinding noise
1. sticking pistons in calipers from breakdown/cracking of phenolic/plastic pistons
2. water corrosion in system blocking brake fluid return somewhere in system
3. front brake flex lines broken down internally blocking fluid return preventing brake piston pad return
4. Pads worn down metal against metal
hows the cowboy hubby holding out on the Aero repairs? glad to hear those cowkid girls are doing great.
Had both warning lights on in dashboard, yellow Rear-Anti-Lock and read Brakes.
Fluid level OK, both break light bulbs work, hand break fully released.
Took the vehicle to the shop, front and rear breaks mechanically OK.
Pulled the harness of the RABS module attached to the right above the throttle pedal --> yellow Rear Anti-Lock light off. Plugged the harness back in --> yellow light on again.
At the front of the break fluid reservoir, there is black connector with two black wires. With ignition off, wiggled that, pulled/ pushed back & forth a bit, turned the key into ignition position - both warning lights gone.
With ignition off, pulled the connector off, saw greenish corrosion inside its female pins. With a tiny round metal brush (needle, safety pin or tiny screw driver should work, too), brushed the connectors' inside. With a small pair of pliers, crimped each one a bit tighter.
Pushed connector back on, ignition on, all fine.
(just as a side note: on my 1990 4L Aerostar, there is also a 3-wire-harness at the right side of the break fluid reservoir, but disconnecting/ reconnecting that one did not help)
That switch on the front of the master cylinder is for the shuttle valve that shuts off either the front or back fluid circuits if one of them should leak. If the shuttle valve shuttles, the switch is supposed to turn on the brake light. That switch port is not water proof, so moisture can build up in there and generate the corrosion that shorts the switch out, causing the brake light to come on. That will disable all the functions that check the brake system before working, such as the cruise control, 4th gear torque converter lock up, and (obviously) the ABS.
The other connector on the side of the master cylinder is the fluid level detector. Both switches have provisions to prevent you from disabling them by unplugging the connectors. I guess if the connectors themselves are corroded, that can prevent them from making proper contact with the switches, triggering the brake lights.
got the green snot corrosion in the shuttle valve switch or shuttle valve stuck to one side?
Time to inspect and replace all the front calipers and rear brake cylinders or at least their seals and completely flush the whole system. Water/moisture/water vapor contaminated. Will rust the whole system out from the inside.
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