I have a F350 2008... And had the same problem...I replaced my BRAKE PRESSURE SWITCH...a 10 minute job..BAM got my cruise back...I got the switch from Orielys ( sp ) for $12..

 

Having the same problem, no pattern, it'll work in the mornings sometimes, in the evenings sometimes, cold, hot, it has a mind of it's own. I read on this thread about the deactivator switch so I just went to Autozone, bought one and put it on, no good. Does anybody else have any ideas? Thanks in advance.

 

I had this same issue. My truck was at the dealership for 7 days! They said they fixed it but cruise still didnt work when I got it back? so I had to figure it out myself. Check up over the brake pedal and make sure no wiring or wire looms are touching the brake pedal at all, if you have adjustable pedals make sure they clear all the way out and in. any pressure on the brake pedal arm will will not allow the cruise to be set, and/or cancel the cruise. This is what my issue was, the factory wire loom was touching the brake arm when pedal was adjusted out to a certain point.

 

You need to replace the brake pressure sensor, not the one on the brake pedal but the one located on the bottom side of the master cylinder. I believe the part# is 3L3Z 95924 go to ford and have them look it up. Then have them show you the diagram so you know exactly what you need to do.

Remove the inner wheel well on the drivers side, you will be able to get to the bottom of the master cylinder easily. Un-clip the harness from the sensor, remove (unscrew) the sensor, replace (screw in) the new sensor and reconnect the harness.

I didnt loose any brake fluid doing this process and you wont either so no need to bleed or anything like that. Its all plug and play, real basic stuff. Truly hopes this helps you as it did me.

I believe the cruise control is deactivated by this sensor, therefore its not going to engage if the computer detects a problem with the sensor. The switch on the brake pedel is just for brake lights.