Hello,

I created an account here has I haven't been able to find a whole lot of information else where. Last year I bought a 1994 F250 4x4, w/ 460 & E4OD tranny. Everything was working fine up until 2 days ago when the CC quit on me. The thing is, it stopped working while it was in use. I was driving down a slight descend on the road and the cruise just gave up, almost as if I hit the off button on the steering wheel or pressed the brake pedal.

I made sure the horn still works and I've checked all the fuses in the interior fuse panel and the box in the engine bay. All 3 brake lights are operative as well. When I bought the truck I also replaced the Master Cylinder deactivation switch, so that's brand new. I also ran a KOEO test and got code 111 (all clear), and then ran a KOER test and got code 111 again with nothing stored in memory. Next I checked the CC cable coming from the servo and it's fine. I'm not sure how to check the servo intself nor the brake pressure and on/off switches. Any insight on what this could be would be greatly appreciated.

 

This is a 2014 post from subford and he is what I consider an expert on this forum. I take no credit except copy and paste. Sandy

The speed control system is designed to automatically maintain vehicle speed at any driver-selected speed above approximately 30 mph and below approximately 125 mph. The system is comprised of an electronic servo which consists of a throttle actuator with integrated electronics and other parts including an actuator cable, horn relay, driver control switches, a brake lamp switch and a deactivator switch. The speed signal is generated by the Programmable Speedometer/Odometer Module (PSOM). The electronic servo is mounted in the engine compartment and is connected to the throttle linkage with an actuator cable.

 

I think I've read the thread you're referring to. Many older posts regarding CC have lost images for wiring diagrams and such. If anyone has such images or knows how to test the various component in the CC system that'd be a big help.

 

First thing to try is use your foot to pull up on the brake pedal while trying to engage CC. Could just be brake switch out of adjustment.

 

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Are you sure his 250 has electric cruise control? I thought 250s/350s were vacuum controlled like my 92 f150 and the previous generation. Check the hoses if it is a vacuum system. Dry rot along the line to or rusted on the vaccum cansister can make older system fail to maintain vacuum or the setting.

 

Yes the vacuum dump valve will disengauge the Speed Control as a safety back-up to the electronic brake switch but if you have electronic problems with it as soon as the dump valve is closed the Speed Control will start back up again.

The above post is from a subford 2009 post. Sandy

 

1992 was the last vacuum controlled speed control system. His 1994 is electric controlled.

 

Alright, so with weather permitting I've finally had a chance to look at this and start some trouble shooting. First I hopped under the dash and unplugged the connector for the speed control amplifier. I measured resistance on the LB/BK wire while pressing the buttons on the steering wheel and everything checked out to be within tolerances of the sheet provided above. I repeated this while getting a friend to turn the steering wheel and only saw fluctuations of >1ohm. So the buttons are good.

I checked all fuses in both fuse boxes so nothing wrong there.

I checked to make sure that the P/O wire on pin 7 going to the servo was getting 12v while the ignition was in Run. That was good.

I checked the BL/Y wire coming from the brake pressure switch which was getting 12v when the engine was not running (I do have a question about this. Should it NOT receive 12v when the engine is running? IE when the brake system has pressure?)

I then checked the the T/LB wire going to pin 4 on the CC servo which comes from the brake on/off switch, which was open when I was doing nothing and closed when I applied my foot to the brake.

Finally I checked the cable coming from the servo going to the throttle. I made sure it had a connection on both ends and that there were no breaks in the middle of it. It too was good.

So assuming I checked the brake pressure switch correctly, this leaves the servo itself. I called my local ford dealer and they said that they don't make the anymore (of course) but the guy did give a part number of F8UZ-9C735-AA.

 

Fantastic. This should be in the FAQ section.

 

Update.

I've finally had time to install a new servo that I bought a while ago (thanks corona) and everything seems to be working now. Thanks again to all of you for providing troubleshooting tips and diagrams.

 

Thanks for the year info and the troubleshooting chart. I’m having some issues with my 1993 5.0 and this will be a great resource.

Roger