[updated:LAST EDITED ON 19-Nov-01 AT 07:50 PM (EST)]i have a 92 f150 two wheel drive that the brake warning light and the antilock warning light come on most of the time. seems to be no regular pattern of when they are on but they are always on together.i have tried checking the fluid level switch and the park brake switch. I have a haynes repair manual that shows there is a dual brake warning diode resistor in the wiring but i do not know where to look for it . I cannot find it in the power distribution box where i thought it would probably be. can anyone tell me where to find this component.;-)

 

I had the same problem with my 88 F250 with the emergency break and antilock light staying on. The problem was that my brake fluid was low because I had a leak in one of the break lines. I replaced the line and filled up with break fluid and it fixed the problem. I'd check to see if you have enough break fluid or even a leak in one of your break lines.

Good luck

 

I jumpered the fluid levell switch to eliminate it but it still does it . my fluid level isnt going down and the brakes work fine. still would really like to know where the dual brake warning warning resistor diode is. this is the next in line according to the wiring diagram.

 

There should be a sensor on the top of the rear end.That would be a place to check.

Good luck

 

[updated:LAST EDITED ON 24-Nov-01 AT 10:33 AM (EST)]When you find that diode, let me know its location. I've had the same problem for years and it's drivin' me nuts! (Hate warning lights on, too stubborn to remove the light).

I've done all the obvious things, and pulled, cleaned, and tested that sensor atop the third member.

Eddie

 

In the 89 factory wiring manual it is listed as 44 inches from the parking brake switch. Thats all it says.

 

removed and cleaned rear axle sensor. didnt find any fillings or anything on it but gave it a wipe anyways.will have to try it for a while to see if light comes back on again since it has been off lately . I had kinda ruled this sensor out because i lost my speedometer and a repair shop repaced my "vehicle speed sensor f85z-2l373-ab".I thought that this was the same sensor that ran the ABS but after looking at my repair manual i do see that there is another sensor but it must be in the transmission since there is only one sensor in the differential. dont think I will find the diode if the only clue to finding it is 44 inches from the park brake switch that could be anywhere.

 

[updated:LAST EDITED ON 06-Dec-01 AT 02:50 AM (EST)]under the dash, near the e-brake bracket, there should be a grey plug with nothing plugged in it -- this is the diagnostic wire. When one or both of the brake lights come on:
1 DO NOT turn off the engine. Put the truck in neutral and set the brake.

2. take a jumper wire (a screwdriver will work) and touch this wire to any ground.

3. look at the RABS light and count the number of flashes.

4. now you can shut the key off if you like

if you can get this code, I can tell you what the manual says it is. These codes aren't in the Haynes or Chilton manuals, just the factory manual. If you have one there is a picture of where the plug is. If you can't find the plug, email me and I will see about scanning the diagram and sending it to you.
Good luck

cbyoung@ix.netcom.com

 

According to the Ford EVTM (Electrical Vacuum Troubleshooting Manual),
the diode/resistor is located within the wiring harness "6.7 inches from c202". C202 is the big 72 pin connector at the driver side, rear corner of the engine compartment. The diode resistor assembly is taped inside the harness between C202 and the engine compartment fusebox, you'd have to cut the harness open to find it. You could test the diode by checking to see if it has continuity in either direction with an ohmmeter. This could be done without accessing the diode/resistor if you use the diagram to find where the wiring to the diode/resistor is accessible. The resistor can be purchased locally if necessary, here's the spec: 1000 ohm, .5W resistor.
Refer to these TSB's for info on diodes to use. TSB 96-24-6 and 89-2-8

That said, the most common cause for this is a bad RABS valve (down on the frame rail below the master cylinder, it is the hydraulic solenoid that pulses te rear brakes in an antilock situation). To test the valve, check for continuity (with valve unplugged) between the terminal of the valve that connects to the light blue/red wire and the case of the valve. The resistance should be around 22,000 ohms, if it is significantly lower than that, replace the RABS valve and bleed the system. There is a switch that trips inside the valve when the valve fails internally, and the resistance goes from 22,000 to 0 ohms. The control module responds to this by turning on yellow and red brake warning lights.


Other causes would be low fluid, or a bad control module.

Hope this helps,
Brian