RABS light won't go out

mike2112 · #1 (**permalink**) 11-18-2005, 10:04 PM

OK, I've posted this elsewhere and gotten very little response. Maybe someone more "homegrown" can help out.

Nothing new here, just an ABS light that won't go out. I have read through all the ABS posts and am still perplexed. 1987 F-150, 302, 2WD, auto. Here's what happens: turn vehicle on, light comes on for a couple of seconds, then goes out for a couple of seconds, then comes on and stays on. I hear a little click when the light goes out. I have replaced the speed sensor with a new one from Ford, I have checked the wiring from the speed sensor, and have checked the wiring at the master cylinder. When I ground the black/orange wire, I get no codes. The light does not flash, it is just on. All other lights are OK. I have read in other posts that the black/orange wire connects to a red wire. I don't seem to have such a red wire. My black/orange is just hanging out there by itself. Could this be causing my light to stay on? Where the hell is this red wire? Where does it go? Where has it gone? Also, coming out from the side of the truck, next to the emergency brake, is a lt.blue/black wire that looks like some test connection. Any clue what this is? Thanks for any help. Phantom lights really put me over the edge.

SwOkcOffRoader · #2 (**permalink**) 11-21-2005, 06:04 PM

well, i dont know diddley about ABS systems, but i can share an experience with ya...my mom has a 92 Ford Aerostar minivan, and the rear ABS light came on one day...i couldnt find anything wrong with the brake system what-so-ever, i was losing my mind over the matter..well a couple days later her battery went dead...turned out the alternator was bad and low voltage in the system caused the light to come on....i have come across this before, sometimes low voltage can cause the "idiot" lights to do strange things....im not saying this is YOUR problem, but you might look into it just in case....good luck with it.....

cigarxtc · #3 (**permalink**) 11-22-2005, 09:13 AM

Heya Mike, I also would have no clue there. But my two guesses would be to first flush and fill with new brake fluid and give it a 15minute highway and city test run. Then my second thing to try would be to physically disconnect every wire connector inline from the ABS light down to the sensors one by one, and spray them with electrical contact cleaner spray as you work your way down. Then give it another test run on the street. My thinking is if there is any crud in the brake fluid on any of the sensors or if there is corrosion or dirt in the electrical wire connections that may be causing it. But that is just what I would do.

Silver Streak · #4 (**permalink**) 11-22-2005, 05:19 PM

Pull the diff cover off and see if the tone ring is contaminated with crap. If the teeth get filled with sludge from the rear end the sensor has trouble reading the gear. It's probably time to change the diff fluid anyway.

rogerf100 · #5 (**permalink**) 11-23-2005, 01:21 PM

I had an ABS light come on in a 1991 Aerostar that had rear ABS. It was a bad sensor but also the rear brakes would lock up in a hard stop. I replaced the sensor and it was back to normal braking.

mike2112 · #6 (**permalink**) 11-25-2005, 06:03 PM

Thanks for the suggestions. I have quietly been suspecting the ring in the diff. I changed the fluid about 10K ago, but didn't look inside too closely. I'll try the wires, too. God, I hate wires and lights!!! This light has been on for years. It's amazing that a system so notorious for being so problematic can have a bulb that never burns out, even when it is constantly on. Go figure.