Hello everyone! First off, my name is David, but my friends call me Dave. I'm the proud owner of a 2003 F150 Fx4 crew cab. I bought the truck almost 5 yrs ago and everything ran fine.....until last year. My cruise control quit working. I've been researching the forums and did the test with the key in the on position and running the diagnostic test. It lead me to the deactivator switch by the master cylinder. I replaced it with a new one and it worked great afterwards. Fast forward to a week later. On the way to work I turned it on, no "cruise" light on the dash but when I set the cruise, it turned the light on and set the speed. A few miles down the road it just shuts off! It's been repeating this behavior for the past three weeks now. After that, it won't turn on for the rest of the day. It'll replay the same behavior day in day out.

 

Replace the pressure switch with a Ford part.
Good luck.

 

Could it be as simple as that? I did replace it with a BDM(?) part I think. It wasn't the motorcraft/Ford part but a part that was compatible with my truck per Advance Auto Parts website

 

It's as simple as that.
Those parts are not made to Ford specs.
This may sound unbelievable but the make you used is calibrated....too sensitive.....
What that means is under hood heat expands the brake fluid causing the switch to open.
Therefore no CC.
Sound familiar to you?
Been there and proved it with 2 BWD parts then a Ford part.
Good luck.

 

And here I was thinking it was maybe a loose connection but hopefully I can find the right ford part in my area. Thanks!!

 

Here is what you can do to verify the condition.
When it acts up, put a short across the plug and try it again.
If the CC works without dropping out over the test period you know it is the switch.
Also before you do this, test the switch for being open when the CC stops working.
If you do the shunt test, 'please do not' run with it as away to defeat it for safety reasons because you will only have the brake switch as a CC knock off and the manual switch.
Good luck.

 

What do you mean by placing a short across the switch? The BWD and the motorcraft part I've found both have the plug that goes into the master cylinder and a plug on the other end. I had to cut that plug off and splice the wires to hook up to the other wires leading into the wire assy.

 

THE SWITCH IS NORMALLY CLOSED until pressure opens it.
IF IT OPENS from brake system pressure YOU WILL HAVE NO CC.
Placing a short across the switch or the cable will act the same as the normally closed switch.
It supplies power to the CC system.
Your just testing to verify the switch is or is not open at the time of CC failure..
The word shunt means the same thing as a short.
I cannot make it any simpler.
Good luck.