Hi, been troubleshooting my 96 F-150, RABS light which stays on continuously. Checked code and got 12. Ford test #1: disconnect and reconnect O/B wire under dash turn key to 'on' and see if brake light comes on. It doesn't, I only get the RABS light. Remaining steps didn't clarify problem.. Tried some of the other steps: Checked Yellow and Green wires at master cylinder for ground shorts and there aren't any. Float moves freely. Also tried pushing down on float w/ engine running and brake light didn't turn on. If I short the Y and G wires to ground brake lights. Also, don't see short between green and yellow wire terminals on master cylinder w/ connector removed. Ford's simplified shematic for Code 12 troubleshooting shows them interconnected w/i the master cylinder before connection to the float switch (which is supposed to be normally open)... Does something besides the float being low have to be true for the red brake light to turn on (and interconnect the G and Y leads)?

Anyway maybe this is sort of a Red Herring. I think I'll reblace the RABS controller.. Too hard to disconnect ignition switch connector to eliminate it as a possible cause...

any thought?

thanks

Mitch

 

According to my book you should run the test again and if you still get code 12 then you should replace the control module (should, I think, be on top of the transmission tunnel and behind the ash tray). Alternatively you could forget about it as the RABS is not much use anyway. Good luck.

 

The question I'm getting at is: the float switch conn'n on MC has 3 contacts (gnd, y and gr on harness that mates with it). According to Ford schematic, the Y and G wires connect to contacts on the MC that both are internally wired to one pole of a normally open switch. The other pole is the Gnd or output. Question is, if I remove the connector and attach an ohmmeter between the contacts on the MC that the G and Y wires would use I don't get continuity. Also, I don't get continuity between either of these two contact and the third when the float is pushed down. Shouldn't pushing the float down close the switch??? Do I have a damaged switch and can it be replaced?

 

You are correct. If the fluid gets low the sensor should cause the red light to come on in the dash and will turn on the ABS light also. However, as I understand it, your red light is not on so even if faulty, the fluid level sensor is not the cause of your ABS light. The bulb in your red light is good, right? It does show red when you apply the parking brake?

 

Light is good. Bought new resevoir and it acts as Ford describes. Haven't finished installing yet. From what I read controller is supposed to see 12V on Pin 2. Only have it on Green wire.. Thus 2 wires not being connected in resevoir would cause controller to see low voltage..


This is the 'bad' resevoir ckt:

Y_______Open
Green___ Open _______/ ._____________Black
| N.O. Switch

This is what it should be:

Y__________
Green______|_______/ ._____________Black
N.O. Switch
Mitch

 

Why are you bothering to fix a system that barely worked when it was brand new? Save yourself a ton of time, money and aggravation with a small piece of brake line in place of the valve. Pull the fuse for it, take the bulb out of the dash, and never worry about it again.

Ford's RABS in these trucks is nearly worthless.

 

Mitch, good detective work on the sensor. You may well be right. Please post back with the results of the new resevoir. I agree with Andym that the RABS is not much use but I don`t agree with bypassing the valve body as this has the proportioning valve in it. Having said that about the RABS I went to considerable trouble and expense to get mine working, just because it was there. Good luck with new parts.

 

How does it have the proportioning valve in it with only the brake lines to the rear going through? If it was also the proportioning valve, wouldn't it also have the front brake lines connected?

 

You are quite correct. Just before I wrote that last post I had been looking at a cutaway diagram of the Chevy RWAL system that I had been working on for a friend. I got confused. Too many irons in the fire, I suppose.

 

The new resevoir fixed the problem. Strangely, after finishing up with the bleeding (I also did pads and rotors) I disconnected and reconnected the O/Bla and red ABS wires. According to the Ford manual this is supposed to kill the keepalive signal and cause the abs computer to clear. Started engine, brake light blinked as it is supposed to and abs light stayed on. At the end of the bloc shut off engine restarted, no abs light anymore (and for half a dozen other trips since then). So, loosing 12 Volts on the Y wire was the problem.

thanks

Mitch

 

Glad you got it fixed and thank you for posting the results of your fix. I`m sure it will be useful to many in the `87-`96 forum where RABS problems are frequent. Also it is worth changing the brake fluid every few years to keep the RABS valve body from clogging up.

 

This is what it should be:

Y__________
Green______|_______/ ._____________Black
N.O. Switch

So why not connect the Y______Green wires together?
(My reservoir is NEVER low - because i check under-hood fluids weekly)

 

That's great but the guy who posted this more than 8 years ago probably doesn't even own the truck anymore.

 

That's great but... don't you think the information comes in handy for (present/future) people w/ same or near same problem? Don't be so narrow minded.....

 

works for me I'm still trying to figure out what he did. what is the O/ bla ? orange black wire?? where is this wire?