Lord Dark Star, did you get your cruise control working?

 

I am also having trouble with my cruise control. Did you get yours fixed. How do you test the spd control amplifier?

 

I finally got around to working on the cruise control issue with my '86 F-150. My suspicion was that the issue involved the vacuum dump switch that is actuated when the brake pedal is depressed. In my case, this switch was fully opened when the brake pedal was in its resting position (foot not on the brake). With a little help from a local Ford dealer's parts department, I found that to adjust the switch, one has to depress the brake pedal, then push (not twist) the switch towards the brake pedal as far as possible (somewhat difficult, but not impossible). The brake pedal is then released and should return to its resting position and automatically adjust the 'throw' of the vacuum dump switch. If successful, the vacuum dump switch is fully depressed. When the brake is actuated, the switch opens dumping the vacuum to the cruise control. The cruise control on my truck now works!(yea) I hope this information will prove helpful for others with a similar issue.

 

Thanks for posting what seems to have worked!

Rep points for that.

 

Glad that was it. FWIW, I actually own a Rotunda tester for the vacuum cruise control systems.

 

Bumping up this old thread because it works!

My cruise had been working well, then it started being fussy ... sometimes working, sometimes not ... and then it quit entirely. The whole system (module, harness, tilt column and wheel, etc.) is a transplant from a donor truck, much like all the options I wanted on Clyde but it didn't have as OE.

I finally got around to digging into it. I had disappointing results running through the diagnostic tests from the service manual (I have a complete set that I acquired years ago) and was ready to give up but I decided to give FTE a try and hit this thread. Crawled under the dash one more time, made this quick and easy adjustment and the test drive was a success. I'm still smiling and it was three days ago!

THANK YOU Lord Dark Star!
Thank you FTE!
and thanks to all the others who participated in the past, the ancient past and in the present to make this site such a valuable asset to us old truck lovers.

The information is here, you just have to look for it!

 

Did you check with the wheel off, there needs to be THREE brushes in the column, two are next to each other on the right side, and a smaller one closer to the center of the column.
My cruse never worked either, until Gary pointed out I did not have the "ground brush" for the cruise. installed the ground brush and TA, DA.... Cruise works!

Ya Need the one marked in Purple, (I think, it's been a while) without it....no cruise....

 

I know this is an older thread...but here goes... I have an 87 F150 with the 5.0L and my cruise is also not working. When you say above that you pushed the switch towards the brake pedal while the brake pedal was depressed, is the switch on some sort of slide assembly that you loosened to move it? after moving you presumably tightened it up? correct?

 

It did not sound like he had to loosen anything.
It sounds like you push the brake pedal down as far as it will go.
Then you push the CC switch to the pedal all the way and this un-locks the adjusting part so it will move back up but don't you move it!
You let the brake pedal back up and this pushes the CC switch back up (adjusting) till the pedal stops locking the CC switch in place.

I could be wrong but that is what I got from reading his post from 11 years ago.
Dave ----

 

Is this the vacuum line and switch in question that needs to be moved forward?? the flat rectangular plate that the white round plastic rod is touched by is the
brake pedal...right? so from my perspective, would you not be pushing the switch mechanism down towards the brake pedal when it's depressed, then when
it's released it would depress the white rod releasing any vacuum built up... I think that is what you saying Dave.

 

Yes kind of if I under stand you right.
The white part is the plunger part that hits the pedal.
The black part or the body of the switch is what needs to be pushed to the pedal when the pedal is pushed down.
Then when you let the pedal up it will push the black body up till the pedal stops.
at that point the black body should be locked in from what I under stand.

I dont have CC, wish I did, so I dont know this for sure.
Dave ----

 

However the switch works, the vacuum part of it releases the vacuum when the brake pedal is depressed. This quickly exhausts the vacuum out of the servo so the throttle drops back quickly. If the vacuum switch is not adjusted correctly, it can be a big vacuum leak and the servo will never be able to pull the throttle cable.

 

Or worst not turn off the CC when you step on the brake pedal
Dave ----

 

It will turn off, but it will just slowly release the throttle.

 

So if the plunger was not moved when the pedal was pushed how would it slowly release the throttle?
Dose the brake light feed back to the "brain" and start to cut back vacuum?
Dave ----