This morning the ABS and brake light started coming on and staying on on a friends '94 CTD. He says that when he's hauling his trailer he's got trailer brakes when he manually uses the brake box, but nothing when he uses the brake pedal. I know in the '98 and above its normally the speed sensor that you change, I'm just not sure with the '97 and lower. Thanks in advance for any help.

 

sounds like he may have a hot wire rubbing on something in the main harness.

 

That's what I was thinking, butI do know that on most of the older trucks both of the lights are on most of the time.

 

I'n not sure how the older ones work. . .but there could be a pressure transducer on the brake line or the master cylinder that has gone out that works the brakes. . .