if that's the case, then all that's needed is to remove the bulb and no more problema!

 

But then you don't have rear antilock brakes, and you paid for them.

 

I'm just frustrated. I bet it's one of the two valves below the MC, everything else seems fine. I've been able to fix 95% of the problems this Aerostar had except (you guessed it), the RABS.

 

I'm pretty sure it's not a hall-effect, but a sealed reed switch (magnetic switch).

You can't test a hall-effect sensor the way the FSM mentions to (test for zero ohms).

Hall-effect sensors have a variable voltage output, which the detector circuit has to interpret. Good for high-speed, accurate pulses and long sensor life. Not ideal for a float sensor that rarely changes state.

 

That resistor in the diode/resistor pack looks like what's referred to as a pull-up resistor in digital electronics. It would not take much of a short to ground anywhere downstream of that (between it and the RABS module) to have the module see a ground reference level.

Yeah, I can imagine something like an ignition switch that has a bit of crap in it doing that: getting just low enough resistance to pull the circuit down to a level that the RABS thinks is close enough to a short.

Can you take a couple pics of that?

From the diagrams, if you really have two connectors on the reservoir, it doesn't even match Ford's own diagram for 1997. The diagram has the harness from the reservoir to the PDWS being an integrated harness, non-detachable from the reservoir, with the PDWS end of the harness being C164: no connector for PDWS on the reservoir end. Only one connector, for the Fluid level switch.

If you've changed the reservoir and still get the code 12, I think I'd test the Ign. switch (after you've tested at the fluid level switch as I've posted above, for circuit resistance ~1000 ohms and found it wrong). If you've got crud in the switch, it can be tested but you're going to have to do some work: disconnect the Ign. switch's connector, test for resistance between the T/LG wire's terminal on the switch and ground. Should be infinite resistance in all switch positions except START.

This whole situation screams for a bunch of testing with an ohmmeter, really. I think I've written enough on the topic.

 

below are pics of the new reservoir and different connector; (has the black plug extension which mine does not have or need).

the RABS light is OFF today, 'intermittent' is the best I can describe it; it was always coming ON and staying ON, then the last few days it goes through its self-check and comes back to ON, other days it goes OFF. today it has stayed OFF.

but after messing with the existing reservoir connector and forcing the float up and down, (I had to buy a new reservoir to understand where the float is), the RABS light has started to stay OFF, I shut the engine, come back later, it stays ON, do it again, it stays OFF.

you might be right in that the entire problem could be the ignition switch, it does feel a bit sticky-rough and not smooth, I went through all the troubleshooting steps in the FSM, and I got as far as "REPLACE IGNITION SWITCH", which I didn't replace.

previously I installed a new Diode and Resistor, (got the parts at Radio Shack), turned out the old diode and resistor tested good after I replaced them.

 

I think the float activates the switch when it is too low, which completes a circuit between the wiring harness to ground , thus triggering the warning light, and other things. I think the connector in the wiring has 2 pins that are shorted by the connector of the reservoir warning switch, so that if you try to disable the warning by pulling the connector out, it detects that, and again, sets the warning.

So can you try this test: Separate the wiring harness connector from the reservoir connector, and short the two pins in the connector on the wiring harness. This should turn off the warning light and take the float switch out as a variable. Now drive around and see if your warning light still comes on. If it does, then the problem is elsewhere, possibly your ignition switch.

 

Shorting the pins closes the loop in the system. Which is what triggers the ABS to start with.

The whole system is a normally open contacter at any sensor. Close any one of them and it fails. The rest is just resistant diodes.

 

You may be right. Looking at Jose's pics, it looks as if the switch is part of the connector, and not inside the reservoir. If so, the magnet in the float acts through the reservoir body.

And the situation you describe is what Ford (& others) use for the airbags, which, when disconnected, short themselves (on the airbag end of the connector) to prevent static electricity from setting them off whilst handling them.

However, the body harness connector doesn't appear that sophisticated, just staring at it.

When I get a chance, I'll take one apart.

Jose, it just realized on me: my 982 ohm reading earlier was with the parking brake set, so I was just measuring the resister in the diode/resistor element. If you do your resistance check and don't have the parking brake set, you probably will see a very much higher resistance. Try measuring it with both the parking brake set, and without.

 

the grey connector shown in the pictures is magnetized; I put a magnet to it and it sticks to the plastic. I have no clue what's below the float inside the reservoirs but it might be another magnet?

I temporarily installed the new grey connector (the one shown in the pictures) under the old reservoir presently in my van; It made no difference, or did it? The RABS light has been staying OFF, (but comes back ON at times); To clarify: the RABS yellow light always goes through its Self-Check but now goes OFF sometimes and/or comes ON sometimes.

I don't know if this change to intermittent ON-OFF is due to me pulling and pushing on the Float trying to unstick it from the bottom in the old reservoir which is still in the van; (it seems to have helped, I am finally seeing something change);

I also cleaned the old grey connector contacts (the old grey connector is removable too), I applied a magnet to it too, and it responded the same way as the new grey connector, so I reinstalled it. Since doing that, the RABS light has been staying OFF intermittently but sometimes comes back ON. Very weird, I am ready to conclude the problem is in the old reservoir or in the Ignition Switch. In other words, a mechanical issue, not electronic.

I haven't done any ohmeter measuring yet, been messing with my work schedule since Thanksgiving Day, changing oil & filter, (it needed an oil & filter change bad), fixing a leaking quick-connect heater hose, (I installed a splice instead of replacing the hose which finally resolved the drop-by-drop coolant leak).

 

In trying to view video notive the link didn't work. Is Muffinman still around with the videos? TIA, BRGDS,
p.