The cruise control is not working in my 2001 F150 Lariat. Checked 2 fuses under the dash and they were fine. Is there an easy fix I am missing?

 

No. After checking a whole two fuses, it gets hard.

 

projectSHO89,

Thanks for your reply. I think I might know you. Send me a pic of the top of your head so "I can remove all doubt."

 

Did you check the fuse under the hood, #15 IIRC is the one? It should be a 2amp, my new to me 2004 had a 10amp in the slot blown when I got it. A 2amp or even a 5amp blows immediatley so I have given up untill I get a chance to have it diagnosed. My local Ford dealer wants $92 for that so I plan to take it to an independent garage that comes highly recommended and charges $45. Jim.

 

Leaking brake pressure switch on the master cylinder?

 

First thing to check is the fuse that was installed as per the recall a few years back. If the above switch is leaking it will blow that fuse.

 

Yes, has the recall been done?
Wouldn't want you to end up like this!

 

Yes the recall modification has been done. (june 09). Yes the master
cylinder pressure switch is leaking. And yes the 2amp fuse in the harness
was blown. I replaced that fuse with a 5amp. Still not working.
My under the hood fuse box does not have a #15 fuse. It is a blank
space that won't accept a fuse.

I tried the self test diagnostic. The cruise light flashed on when I pressed the
"off" button. It flashed again when I pressed the "on" button. I then pressed the "res." button. Nothing happens. Now what.???????

Thanks in advance.

 

OK david, I think you are toying with us

But, with internet, one never knows for sure. And I don't want someone's house to burn down, so I guess I better go and spell it all out, just in case.

The truck came from the factory with a Texas Instruments made pressure switch screwed into the master cylinder. This switch is "closed" when there is no foot pressure on the brake. It was live 24/7 with 12 volts from a 20 amp or so fuse. Power was routed through the closed switch and on to the cruise control servo. This power would pull the clutch that attaches the servo action onto the throttle. The idea was that this brake fluid operated pressure switch was the secondary safety, in case the brake electrical switch didn't turn off the cruise control. This secondary safety is equivalent to the vacuum "dump valve" that was just above the brake pedal on the previous all-vacuum operated generation of cruise control.

Pressing on the brake pedal, besides opening the cabin-mounted brake electrical switch, would pressurize the brake system. The fluid-operated switch's internal Kevlar diaphragm would flex, pushing the switch contact to "open".

The trouble was, if there ever was the slightest instance of vacuum in the brake system, the Kevlar diaphragm would be bent the wrong way for a bit. This was never in the design specification for the switch. The switch would last about forever if the internal diaphragm was flexed only in the proper direction, but the life was shortened drastically if it bent the other way.

If bent the wrong way, the diaphragm would weaken, and after a lot of use (remember that this diaphragm and switch load/unload each time you press and release the brak pedal, doesn't matter if the cruise is on or not) the diaphragm would start to crack and leak. This allowed brake fluid into the switch's electrical area. Brake fluid would start to conduct the 12 volt current to ground (the body of the master cylinder). This current would start to cook the brake fluid, starting a fire, which would be fed by more brake fluid, and lots of current via the 20 amp fuse. The fire would consume the truck. If parked in a garage, it could consume it and any attached house.

The "fix" was to insert an extra harness into the circuit. The harness has a series 2 amp fuse between the battery feed side and the switch. So the thought is, if the diaphragm breaks down, as current increases, it pops the 2 amp fuse, before much damage occurs. With the fuse popped, no 12 volt power is at the fluid pressure switch any more. And of course the cruise control does not work.

But along comes a guy who says that his cruise doesn't work, finds a blown 2 amp fuse in the safety recall retrofit harness... and replaces it with A 5 AMP FUSE!!! And oh yeah, he sees brake fluid leaking from his pressure switch, too.

 

I went to the Ford dealer yesterday and picked up a new harness and
master brake cylinder pressure sensor. Good news is, it only cost 18 bucks.
Bad news is, my cruise control still isn't working. Help.

Please, I would prefer not getting any replies from Torky2 or ProjectSho89.
You guys have been no help at all. And I think you are both suffering from
a major inferiority complex. It's either that or you have the dreaded
T W L P syndrome.

Thanks in advance to those who really are trying to help.

 

It might be worth checking the cruise control throttle cable where it connects to the throttle body, it is "clipped" in and sometimes the clip will come off and your truck will act like there is no cruise control even though everything works. You will probably have to take the Triton V8 plastic shroud off of the throttle body, then you'll see two cables going to the throttle body. If one of them is loose, then that is likely your problem.

Good luck!

 

Thanks for your reply.

My cruise "light" doesn't come on when I press the "on" switch. Could
the cable still be part of the problem?

Thanks

 

That makes the cable very very unlikely, unless the cruse light happened to burn out at a similar time.

Here are the only other things I can think of:

Steering wheel control switches.
The steering column clockspring.
The cruise control module.

I would say clutch switch, but your lariat is an automatic, right?

 

Is this the switch you are talking about?
Picture from a 2004 F150 Lariat 5.4L

 

No. The 2004 doesn't have the subject switch. You're looking at the fluid level switch connector.