Cuise control problems

91 XR7

Registered User
Cuise control problems (new info??)

Except for the aculator test, i've tested everything and it all basiclly came out to be what the books says it should come out like but it still does not work, even with a diffrent Module and all...

The only `oddity' i seen was like a 11 ohm Ground resistance and like a 7-9 ohm Brake light resistence (i do have ONE 3rd brake light bulb out) and everything else on the same ground circuit (G200) works so a bad ground i can't see.. and the voltage at the Blue/black wire is always at like 7.5V's goes to 12v (battery Voltage) when you press `on' and 0 Volts when you press `off' but the book makes it out like it shoudl be 0Volts when off and like 7.5V when on (When bottons are released)???

Like i said, i have yet to test the acculator since i'm not a big fan of having my engine free rev at what ever RPM it may end up at...

Any thoughts, anyone??? I'm planing a LONG LONG LONG trip (@8,000miles round trip) and cruise control would be SWEET!! :)



Thanks
 
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well it is basiclly the same idea.. i have the `module' (or `speed control ampfier' ) on the brake pedal... and going by '91 Shop manual the switch Voltages are slightly different then in that link...

ON is Bat Voltage
OFF is 0 Volts
Set/accel is 4.5V
coast is 1.5 volts
resume is 6.5 Volts

and my readings are pretty much close to those give/take .25 of a volt.. and the resistence at the switches themselves are in around the middle of the range they are surpose to be in..

I MAY try the Servo test tomorrow night and see, even thou i'm not gonna be a fan of the whole letting the engine rev up when i'm baried under the dash and i can't get at the Ignition switch fast enough.. also i may just `jerry rig' a harness to do it.. we'll see..

Also the Vacuum dump valve at the brake light switch.. is there vacuum there all the time, or only when the Cruise control is working??

thanks for being helpful so far thou :)

also i never checked the voltage of the VSS only the resistence, since that's the only thing the shop manual says to check??? but the speedo works and the ARC kicks in at just about 90MPH when it's surpose to (now THAT i want reprogramed to come on at like 55MPH)

thanks again
 
Hmm, I only reviewed the information for the integrated systems, which is what the SC's have. There are the Ford Systems with a seperate servo system, and those that are integrated into the EEC-IV. Ours is integrated, and all the voltage and resistance values are slightly different. There are also a couple extra things to measure on the seperate system.

For the seperate system the expected values are:

ON is Bat Voltage
OFF is 0 Volts
Set/accel is 4.5V
coast is 1.7 volts
resume is 6.3 Volts

Well within what you see.

Hmm, can't track down any info on the dump valve. They call it a Vacuum Vent valve in the documents but with absolutly no info on it. I would assume vacuum won't be there if the system isn't turned on. As the dump valve dumps vacuum stored by the control that is mounted in the drivers side fender. The control likely doesn't store any vacuum until it is turned on.
 
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A common cause of malfunctioning cruise is not electrical. There is also a mechanical vacuum "switch" on the brake pedal. This is a fail safe that releases vacuum when the brake is pushed to release the throttle. The problem is this is easily knocked out of adjustment so that the valve is constantly open, if it does this the cruise system seems completely dead.

If I remember right the pushbutton on the valve is yellow, and there will be a 3/8" or so vac line running to it. It is on the back of the brake pedal arm, above the brake lamp switch. You need to make sure the brake pedal is pushing this valve fully closed in its "relaxed" position.
 
Unless the Vacuum dump valve is broken.. it's adjusted to spec by my shop manual... like the body of the Valve within 1/16" (0.050 inch) of the `pad' on the brake pedal..

And i'm not gonna play with the servo test tonight, i'm WAY too tired... (been up since 5:30 this morning, and working my *** off till 5:30.. I just want a nice cool shower and Veg out..) but it will happen.. and i'll let you guys know... :)

well '89/90 S/Cs had the `speedo control' intergrated into the EEC-IV the '91-95's had the seperate unit on the brake pedal bracket (Got my extra one from a '92? S/C)

and yah, going by the HTML (Link) and the specs in my book yah a few things are different..but the resistences at the buttons are different but the voltages are... but also the `Buttons at rest' Voltage is different.. mines surpose to be `7.8Volts' where as the EEC-IV one is 6.7V which would give reason to the Voltage difference...

and yah the Vacuum dump valve is attached to the Vacuum side of the piston that pulls the cable.. so Cruise if the cruise control isn't working.. it won't have vacuum.. But if it's `venting' when it's not surpose to me.. then the vacuum will not build up to pull the cable... But i do not notice any `hissing' sounds when i try the cruise control..
 
Well took awhile to do more testing.. and had fun almost blowing up the engine ;) (tach got stuck at 7g's)

ANYWAYS...

Tried the servo test.. hooked it as per the manual.. grounded out the one wire.. i hear a hiss nothign happens.. repeat 3 times.. nothing.. and on the last try before lifting up the car to take off the wheel, ect all of a sudden it was like full throttle...

Well get the wheel off, the inner fender off, ect.. this time i disconnected the throtle cablke at the trottle body :) started it up and tried it again, the cabled moved.. get it to release the vaccumm try it again, nothing... listen at the servo when grounding the wire.. i hear hissing.. repeat a few times.. same thing.. you can see the cable `twitch' when yah gournd the one wire... but not pull it, even if you push the cable it will not hold it...

Also i noticed the cable is rather easy to move, like there's NO resistence to it at all as like I would think it should if it was attached to a vaccum diafram (sp)

Also another tid bit of info..

before it went completely, it used to be a On/off thing about working.. sometimes it did, sometimes it didn't.. Like something was working it's way loose..

I've remove the servo and i'll see what i can do...
 
Well now so this is it...

Buttons are in spec
The Resistences are good through out (Brake light circuit, Servo Valves, and varaible resistor, )
Servo works (now?)

and i replaced the connectors at the Module (`ampifier' ) since two of the `pegs' that hold the wires in were broken...

I have yet to test drive it.. but doing the servo test made it move.. so here's hoping... and if this doesn't work.. i'll just get a Aftermarket one, and see what it'll take to wire it in :)
 
Cuise control

Did you set the upper cable on the t-body linkage? The plastic grommet was broken on mine and worked fine after I replaced and set it. Good luck
 
Pardon?? I haven't really plaied with any adjustents on the Servo motor cable yet... but to me it's `if it worked before...'

But all and all still does not work.. which is slightly p*****g me off right about now... the only thing i can think of at this time.... that i may be the buttons themselves or both `ampifiers' (Module) are gone...
 
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