My cruise control went out on my '97 F150 while I was traveling down a highway last month. It didn't stop working instantly but rather on a gradual basis. I would set the cruise and things would be fine until I hit a mild bump in the road and that's when the cruise shut off, or basically stop holding the trottle in place. It did this numerous times on my travel that day. It was like having a bad wire connection in the system that would be fine while on smooth surface but would disconnect if the truck was jolted slightly. Today it won't work at all when I try to set it.
I checked out the cable from the servo motor to the throttle linkage and all is fine. When I was checking the connection of the wire plug on the servo motor I did discover some type of oil inside the plug. That can't be normal. It makes me wonder if there is something wrong with the motor. Secondly, I removed the airbag from the steering wheel and checked the wire connections to the cruise control switches. Again, all looked fine. Thirdly, I checked the owners manual to where the fuse would be. I could only find a relay to the system. I swooped around identical relays from a different circuit which still resulted in no cruise control. I have no multimeter to check each wire to the system. Basically I'm out of diagnostic ideas and need some advice from people who had this problem or from those who haven't. Any thoughts would be appreciated, even the ones telling me to give it up and just take it to the dealership already!

 

BUBB did the (oil) in the servo connector smell like brake fluid? Fuse 5 in the engine compertment fuse box.Fuses 5& 13 inside fuse box.Without a voltmeter or testlight it will be hard to diagnois this. You can check the brake pressure switch at the brake master cylinder by jumping the 2 wires together and then retesting speed control.Wire colors are green/red and black/yellow. If this fixes it replace switch,DO NOT LEAVE JUMPER IN,this is a backup switch for brake light switch.Let us know of results.

 

Thanks Stan for the reply. I'm going to look at the servo motor plug again tomorrow. From what I remember, the look of the oil was thicker than brake fluid and cleaner too. It almost looked like engine oil but I'm going to take another look. I'm going to look at the fuses you stated as well. Stay tuned.

 

Well Stan, I have to hand it to you! You figured out the problem with my cruise control. The oil that was in the servo motor plug was brake fluid and it came from the brake pressure sensor switch on the master cylinder. I unplugged the wire connector to the pressure switch and it was full of brake fluide as well. I did check the fuses and found them to be okay. I went ahead and jumped the wires together leading to the switch. Took the truck out for a test spin and found the cruise to work once again. To my surprise though, the cruise control shut off when I applied the brake like it normally would. I thought with the brake pressure sensor switch removed from the circuit (by jumping the two wires) the cruise control wouldn't be affected by applying the brake? Well no matter, I'm going to my local Ford dealership to get another switch. Hopefully this will be the end to my problem. Kudos to you again Stan!!