Diagnosing cruse control.

So now that my truck is back up and running decent ive started tackling the little things thats have been on the list for awhile and next one isnt as little as i once thought...
I would really like the cruse control to work so once the truck is super solid i can road trip it or haul with it. I searched a bit and didnt find anything particularly explaing how to diagnose the cruse control but if theres already a thread here about this please let me know.
So basically i press the buttons and nothing happens ive checked the fuse on the block that looks good, ive swaped the horn and controls out to another truck to see if it was the buttons that didnt change anything. and ive compaired to other trucks to see if im missing anything. only thing that is off about mine is on the servo the lower vacuum port is basically just taped up woth electrical tape and theport on the long plastic vacuum block is capped. is there a way i can verify the elecrical is functioning before i try and hook this up?

The EVTM manual for your year has a pretty through diagnosis in it if you can get your hands on one. I would start by pulling your steering wheel and making sure that the two slip ring contacts are not worn out and are clean and lubricated. Next would be to check the vacuum switch mounted on the brake pedal to be sure it's got vacuum and is functioning correctly. Then there is a pin test to do at the cruise module under the dash to make sure the resistance from the buttons on the steering wheel is correct at the module. Then comes the test for the servo module. It's a bit more complicated and I can't remember the details but it's all in the EVTM or maybe someone here has posted the process.

What year is your truck? Does it have a vacuum cruise control or an electric cruise control?

I have diagnostic write-ups for both. If you'd like a copy let me know, PM to me your email address.

gandalf said:

What year is your truck?

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I’m 95% sure he’s working on the truck in his avatar as that’s the one he’s been discussing in other recent threads which means it’s the vacuum version. But you’re right, it should have been asked before I assumed.

Are your write ups by chance posted in the tech section or somewhere else?

aggiediesel01 said:

I’m 95% sure he’s working on the truck in his avatar as that’s the one he’s been discussing in other recent threads which means it’s the vacuum version. But you’re right, it should have been asked before I assumed.

Are your write ups by chance posted in the tech section or somewhere else?

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I got word back from the poster. It's a '91 F350. That puts it right about the change-over time between the two systems. I sent him both files. They are actually posts I copied from somewhere long long ago, from a place far far away.

To the best of my knowledge these files/diagnostics are not posted in the Tech section. I'd be happy to supply them if the Mods ask.

i cant find anything about a vacuum dump valve anywhere alsoi dont see anything on the pedal. i have seen older truck have a vacuum line that goes into the firewall my truck has that same spot on the fore wall but i dont see anything thst it could go too.

Nick_Rego said:

i cant find anything about a vacuum dump valve anywhere alsoi dont see anything on the pedal. i have seen older truck have a vacuum line that goes into the firewall my truck has that same spot on the fore wall but i dont see anything thst it could go too.

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Maybe it's that?

The vacuum dump valve should be mounted at the top of brake pedal on a bracket next to the m/c push rod under the dash. I don't have a picture handy but I'll see if I can dig one up.

aggiediesel01 said:

The vacuum dump valve should be mounted at the top of brake pedal on a bracket next to the m/c push rod under the dash. I don't have a picture handy but I'll see if I can dig one up.

You must be registered for see images attach

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thanks for the picture i found mine definitely not hooked up. would there be a reason someone un hooked it?

Maybe if there was some problem with the servo and someone was working on the system it and then gave up?

If there is a servo problem, most of the late ‘90s ‘80s and early ‘90 ford trucks and maybe cars used the same servo. They just had different throttle cables attached. If your cable is undamaged, you can swap it to another good unit and be on down the road.

aggiediesel01 said:

Maybe if there was some problem with the servo and someone was working on the system it and then gave up?

If there is a servo problem, most of the late ‘90s ‘80s and early ‘90 ford trucks and maybe cars used the same servo. They just had different throttle cables attached. If your cable is undamaged, you can swap it to another good unit and be on down the road.

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Odds are, the cable's plastic sheath will be trashed from age.

gandalf said:

What year is your truck? Does it have a vacuum cruise control or an electric cruise control?

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I also have a 91 I would like to get cruise back on. Could you please send me he

gandalf said:

I got word back from the poster. It's a '91 F350. That puts it right about the change-over time between the two systems. I sent him both files. They are actually posts I copied from somewhere long long ago, from a place far far away.

To the best of my knowledge these files/diagnostics are not posted in the Tech section. I'd be happy to supply them if the Mods ask.

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Could you send me those files also? I have a 91 superduty and would like to get mine working.

Steve Turner said:

I also have a 91 I would like to get cruise back on. Could you please send me he


Could you send me those files also? I have a 91 superduty and would like to get mine working.

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I'll need an email address if you'd like the files. Could you send that to me by PM?