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cruise control broken

tomtoc

tomtoc

2,049
68
Springfield, MO
my cruise control buttons do nothing. isn't that all vacuum operated...so odds are i have a vacuum leak?

my old truck would sort of made a "click" once the cruise "caught". this one makes the same noise, but then cruise doesn't work.

so...best way to check for a vacuum leak dealing with cruise control?
also, it's a manual - is there some switch that could be faulty dealing with the clutch disabling it?
 
john112deere

john112deere

caffeine junkie
Staff member
10,807
406
central Vermont
tomtoc said:
also, it's a manual - is there some switch that could be faulty dealing with the clutch disabling it?
Click to expand...

The clutch pedal position sensor (CPP) does affect the cruise, since it's designed to kick off the cruise if you hit the clutch.

I think if your truck starts when you step on the clutch, but won't crank if the clutch isn't pressed, you can assume that switch is good, though.
 
blacksnapon

blacksnapon

Moderator
Staff member
9,461
301
waynesville,mo.
Theres many checks for an inoperative cruise. Brake switch, clutch switch, module, steering wheel switches, circuitry, and yes, vacuum.
 
mrfixit

mrfixit

Chief Chaotic Engineer
8,334
171
Malfunction Junction, Fidelity MO -or- Mound City,
The brake pedal switch also kicks off the cruise.
The Speed Sensor is the likely culprit tho, in my ops

On edit, I defer completely to Vince.
I do know though, that the SS on the early 90s models were prone to failure.
 
Last edited:
tomtoc

tomtoc

2,049
68
Springfield, MO
checked on the way home - clutch switch works correctly. What's the best way to begin checking the other components
 

NeXtras

973
11
clock spring?
 
O'Rattlecan

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
I would also check the Speed sensor like Tom was suggesting.

The things were prone to getting moisture in them and failing. If you do decide to get a new one, seal it up with a touch of silicon. It's located on the top of your rear differential.

Ryan
 
Lost

Lost

PA Chapter leader
3,288
33
central PA
The box on fender with cable to intake is the 2nd most common problem.

1st would be clock spring but you'd have the no dome light thing and dash light .

Switches in steering wheel or connections is next
 
Mr. Stroker

Mr. Stroker

CASE IH
3,121
67
Michigan
Mine was the module. I took a gamble and got one from a pick your own parts junk yard for 8 bucks.
 
Skandocious

Skandocious

Post Whores Make Me Sick
19,076
655
California
The cruise control is vacuum controlled?! Are you guys sure about that?

If the VSS wasn't working then you'd have bad readings on your speedometer. I don't think the VSS is the problem. I'd follow Larry's advice and check the wiring to the switch -- then follow Mike's advice and maybe use a multimeter to check the connections at the cruise box -- also check the throttle cable that goes from cruise box to throttle body.
 
Mr. Stroker

Mr. Stroker

CASE IH
3,121
67
Michigan
The older ones are Vac operated. Im not sure what year they went to electronic, but i had a 85 F150 and the cruise was Vac and worked flawless. My buddys 89 is Vac as well..
 

eco

646
12
Skandocious said:
The cruise control is vacuum controlled?! Are you guys sure about that?

If the VSS wasn't working then you'd have bad readings on your speedometer. I don't think the VSS is the problem. I'd follow Larry's advice and check the wiring to the switch -- then follow Mike's advice and maybe use a multimeter to check the connections at the cruise box -- also check the throttle cable that goes from cruise box to throttle body.
Click to expand...

Cruise control is vacuum controlled (the one on my van was anyways - I yanked it though). I think that since vacuum is proportional to load, the servo detects an increase in load via a drop in vacuum then opens the throttle accordingly to maintain the speed. Thats why if you are in cruise and you start going up a hill (a load) the motor will rev up (because vacuum droped) to prevent the MPH from lowering.

Besides that, the servo has a vacuum line coming from the plenum and there are other vacuum lines on the servo to route vacuum.
 
Skandocious

Skandocious

Post Whores Make Me Sick
19,076
655
California
Eco isn't your van a gen 8? I always thought that my RPMs increased when going uphill because the cruise was monitoring my speed and saw that it started to decrease, so it compensated and brought the truck back to the right speed -- no vacuum involved. Of course thats what I just assumed, I've got nothing to back that theory.

Are you sure they didn't switch to electronic in the 9th gen? Cuz I don't recall seeing any vac lines going over to my cruise control unit.
 
Mr. Stroker

Mr. Stroker

CASE IH
3,121
67
Michigan
Skan yours is electronic....
 
Mr. Stroker

Mr. Stroker

CASE IH
3,121
67
Michigan
93 not 100 % Sure but i would say yes it should be.
 

eco

646
12
Skandocious said:
Eco isn't your van a gen 8? I always thought that my RPMs increased when going uphill because the cruise was monitoring my speed and saw that it started to decrease, so it compensated and brought the truck back to the right speed -- no vacuum involved. Of course thats what I just assumed, I've got nothing to back that theory.

Are you sure they didn't switch to electronic in the 9th gen? Cuz I don't recall seeing any vac lines going over to my cruise control unit.
Click to expand...

I am not sure what the cutoff year is for the generations, but my van is an 88. Some (all?) rigs with non-computer controlled trannies (C6, AOD etc.) get no vehicle speed data from the trans (mine doesn't anyways) so instead they use vacuum and go by load since a load will slow the vehicle down and vacuum is proportional to load. With an E4OD and an AODE etc. I would imagine that the computer has all the needed data to be able to electronically run the cruise control.
 
Mr. Stroker

Mr. Stroker

CASE IH
3,121
67
Michigan
My buddys 93 is electronic. We think that they switched over to Electronic in 92
 

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