"Rear Anti-Lock" light is on. Been on for as long as I can remember.

'88 F-350.

Any idea what makes this turn on?

 

i have been trying to figuar this same thing out on my 92 f150

 

On steady, normally means the abs sensor in the rear axle is either on the fritz or something in the wiring to it. If its flashing mine was cuz my brake light fuse was blown

 

There should be a one-wire connector taped to the big wire bundle that passes through the firewall near the parking brake pedal. The wire is black with an orange tracer. This is the diagnostic wire for the ABS system, if it is momentarily grounded while the light is on, the ABS system should blink trouble codes on the ABS light. This will give you a better idea of where to look for the problem. If it doesn't blink, check the float switch connection on the master cylinder.

 

So is mine....and I've had the truck since new.

It could be the ring gear sensor at the top of the differential or the M/C reservoir plug as mentioned.

**It also could be that you need to bleed the RABS valve. Which on my truck is located inside the frame rail beneath the drivers seat.**

I can't get a code using EPCNSU2006's method and have come to the conclusion that it must be that my computer is FUBAR'd.

 

I can't get a code either, and I found the float switch connector was broken when I replaced the master cylinder for an unrelated issue. That cured the light for a while, now it is on and off randomly.

 

soft music, candle light, wine

 

Pure Genius QuadDriver. Hahhaha.

I'm not sure whats up with it. Just to throw it out there, I drove through a ditch. ( I was turning around while wheelin' and didn't notice it. ) Thumped into it really hard and the light turned off.

2 minutes later there was a log in the trail I drove over and the bump turned it back on.

Any new idea's?

 

Mine came on took it to the shop and they found out that the ABS Sensor went bad and just needed to be replaced. my 2 cents

 

Seems probable. I'll look into it. Its probably bad.