Cruise control quit

[Chris142]

87 f250 in my sig..I use my cruise every day. Worked friday. Nothing saturday. Has vacuum to the box that pulls on the throttle cable and the fuses are good.

Other than those 2 things i dont know what else to check or how to test anything.i pulled the steering wheel apart. Switches are not serviceable.

Theres a black wire that honks the horn if i ground it and a yellow wire that goes to the cruise switches that do not have power. I do not know if the yellow wires wre supposed to have 12v or are a ground.

Guys on the diesel forums dont know.

 

[JHZR2]

On the my diesel forums it is well known that those vehicles get broken solder joints in the cruise amps... Otherwise those systems are bulletproof, can't imagine yours would be any different.

 

[Chris142]

Whats the cruise amp?

 

[spackard]

Well, on my '92 Acura it was the brake light switch. It has two circuits, one NO and one NC; one of them failed and while I didn't have a solid brake light on I did have a cruise control that wouldn't work until I replaced the switch.

I guessed it was a brake light switch, but there was a diagnostic sequence to follow in the FSM and it confirmed the bad switch.

 

[Chris142]

Mine does not use an electric switch on the brake pedal.it uses a vacuum switch. I tested that by crimping the vacuum hose shut. Thats one of the tests i read about

 

[Merkava_4]

Is the vacuum diaphragm holding vacuum like it's supposed to ?

 

[Chris142]

Originally Posted By: Merkava_4
Is the vacuum diaphragm holding vacuum like it's supposed to ?
dunno. Its a sealed unit.all hard plastic and the cable just comes out of it.

 

[Merkava_4]

Originally Posted By: Chris142
dunno. Its a sealed unit.all hard plastic and the cable just comes out of it.


Is there a vacuum hose going to it ?

 

[Chris142]

Yes and there is vacuum

 

[eljefino]

Aren't ford cruises very interchangeable? Ie something from a taurus might work. I went through this when the clockspring on my grand marquis went out. Grab one from a yard for $10.

You already know they compromised when they made your diesel stuff run on vacuum.

 

[skyactiv]

If you figure it out Chris, let us know what fixed it. There are too many threads like this where the person doesn't ever reply back what fixed the issue.

 

[Chris142]

I dont have much luck with junk yard parts.i always get another dud then i chase my tail even more. I cant find any info on how to diagnose this system and i really do not fully understand how it works

 

[TFB1]

Looking at a '86 T-Bird EVTM, the buttons select various resistance values to tell the amplifier what function has been selected, excepting for "on" all work by providing ground..

On is 12v from horn relay
Off is ground
Resume is a 2200 ground
set/accel is 680 "" ""
coast 120 ohm "" ""

On this diagram LB/BL wire is input to amp from switches/resistors, Y/LG is 12v input from horn relay, should be same color on truck...

 

[Chris142]

I do not have 12v to the on off button.i printed out the diagnostic instructions that cover 83-89 trucks but my wires are the wrong colors so now im really stumped

 

[TFB1]

I have a '93 F-150/250 diagram that colors are listed same the '86 T-Bird.. Main difference is the '93 uses slip rings and the ground is fed from cruise module instead of chassis, resistors and contacts appear same... Of course the '93 has eliminated the vacuum dump...

Find horn relay and check colors, power feed back to cruise activation switch should be same color at both ends(hopefully)...

Btw the black wire is horn and switch assembly ground, should be a Y/LG wire that comes from relay the feeds 12v to the switches and activates relay when horn button is depressed... You have power or the horn would not operate...

 

[zzyzzx]

Originally Posted By: Chris142
Whats the cruise amp?


If it's anything like my 1995 Escort, where I added factory cruise control to it, there is a module just for cruise control.

 

[zzyzzx]

Originally Posted By: eljefino
Aren't ford cruises very interchangeable? Ie something from a taurus might work. I went through this when the clockspring on my grand marquis went out. Grab one from a yard for $10.


I can confirm this, since I think I got the one for my Escort off of a Mustang.

 

[zzyzzx]

Originally Posted By: Chris142
Mine does not use an electric switch on the brake pedal.it uses a vacuum switch. I tested that by crimping the vacuum hose shut. Thats one of the tests i read about


You need to test all the vacuum components with a MityVac to make sure that they are not leaking.

 

[Merkava_4]

Originally Posted By: Chris142
Yes and there is vacuum


In that case, if you disconnect the vacuum hose going to it and connect a vacuum hose from a vacuum pump, the cable should move when applying vacuum. You got one of those Mityvac hand held vacuum pumps ?

 

[TFB1]

There is a modulating valve inside the vacuum servo that regulates throttle opening, just checking it's ability to hold vacuum isn't a conclusive test... If it were leaking likely idle will be effected...

Those servos are all similar on the passenger cars of the period(dunno about trucks), most I've had to do is swap the throttle cable...