had this problem since i got the car all works fine until you hit the brake and theres no vacum dump so the car thinks you are on a hill and puts the gas in,i tell you i nearly shiznit my pants.is there a test for the brake vacum dump or adjustment?
I have no ideas for your fix. My 06 F350 did the same thing. Gave me a little pucker factor. I've got to check and replace my brake switch.
Good luck.
The vacuum dump valve is the safety backup to disable the cruise control in case the speed control amplifier module goes crazy.
This will only disable the cruise as long as you have your foot on the brake.
The brake light circuit should shut off the cruise control module.
Do your brake lights work?
I just had that problem, ordered a brake switch and when I contorted myself under there to check it out. The wiring to the switch was corroded and apart. Put in the new wiring and was back in business.
Check to make sure your brake lights are coming on.
Just an fyi, virtually any car uses the same switch. I accidentally broke mine when i did the pedals on my t-5 swap. I got the new switch out of a 97ish f-150 that had the pedal ripped out.
yes the brake lights work
just had a look at the brake switch and someone has bin in there.from the switch i have green/red(feed) going into the protective loom sleeve which has a green wire cut off just inside.the other wire has bin played with starts green then the wire has bin cut and joined to a green yellow wire which goes to the fuse panel.i gusse the cut off green wire should go to the switch but why has someone done this?
check that the vacuum hoses to the unit inside the fender aren't connected backwards. If I remember, there's 2, one goes to the dump, the other is source. If they were connected to the unit wrong, providing a path by opening the dump might cause that. Otherwise, the amplifier has gone yumpy. I'm working on retrofitting the all integrated non-vac cruise from a crown vic, watch for developments on that, if it works for me, maybe it's something you want to try.
Mine had a green/red wire and a green wire connected to the switch. One of them, I believe, was joined to a yellowish wire a little further along.
this yellow green wire i know is earth wire from household electrical wiring and completes the brake light circuit by going direct to the fuse pannel.i guess that somewhere on the green return (origbuttstuff)from the brake switch it joins the crusie control to cut it out.i only thing i can come up with is the brake light circuit failed (brokern wire)and someone has done this to get the lights working again but in doing so has lost the cut out.
This is the "hot at all times" wire from fuse #1.
Does the green yellow wire look like it was part of the original cable harness or added later? Is it green with a yellow stripe or yellow with a green stripe?
That would be my guess too.
Do you know if the exterior lights on US cars must be modified to comply with UK laws?
It has been more than 60 years since I've been to the UK. Back then you had little turn signal arms that would pop out.
Look at the speed control amplifier to see if any modifications have been made to the green wires there.
After some studying at the university of google, I think I understand what is going on.
In the US the brake lights (red) are also used as the rear turn signals.
In the UK the rear turn signals must be a different color (orange) than the brake lights.
The green wire from your brake switch is spliced to a green/orange wire ( the orange faded to look yellow) thus bypassing the turn signal switches to go directly to the brake lights.
It is, of course more complicated than just this one change.
Are your rear running lights also orange instead of red like in the states and are these used as the turn signals?
Anyhoo, lets just concentrate on what's going on with the cruise control.
The green wire connection at the cruise amplifier must be at ground potential for the cruise to turn on.
The ground is through the brake light bulbs filaments to ground. When the brake switch put voltage on the green wire this took the ground away.
If your green wire is still attached to the turn signal switches and your modification uses the rear running lights as turn signals, the cruise will be getting its ground through the running light bulb filaments to ground.
The cruise would not turn on if the running lights are on.
the wire is yellow with green strips no its not original as for light mods for import,fog light must be added also white side lights which i have euro spec headlights with a side light bulb in.this y/g wire goes from the brake switch to the rear lights which again have bin cut and joined giving me brake lights the speed amp has still the origbuttstuff blocks not moded in any way.is it possible multi function switch(where is it) has failed on this part of the circuit and the wire is a quick cheap fix?.oh by the way thanks for the circuit dia very helpfull
The multifunction switch (which includes the turn signal switches) is on the steering column.
Read my post #12 to see if it makes any sense. I must have been typing the same time you were.
Check if your running lights have any affect on the cruise.
I have a potential fix in mind that will require you verifying some things at your end.
First off, turn on your headlights and see if that disables your cruise.
it will not be until the weekend before i can get back to this will let you know then but im sure the crusie control works with the lights on.the two orange rear lights in the bumper are my turn signals
Ok, you have separate orange lights for turn signals. The headlights will have no effect on cruise.
The fix is to reattach the green brake switch wire that was cut and to cut the green wire that goes to the multifunction/turn signal switch.
1. disconnect the negative battery cable.
2. unplug the connector with the two green wires from the cruise control amplifier.
3. with the ohmmeter function of your multimeter , check for continuity between the cut green wire and the green wires at the connector.
4. if you have continuity, you have to decide which of the two wires at the connector goes to the multifunction switch and which one to the cut.
You can physically follow the wire or cut one and hope you get lucky. check the continuity to see if you cut the correct wire. Guessed wrong? then cut the other wire and splice the first one you cut back together. Do not cut the wire too close to the connector, leave enough wire to work with in case you have to splice it back together.
5. Splice the cut green wire, where the yellow/green wire was added, back into the brake light circuit.
6. replug the cruise amp. connector.
7. reconnect the negative battery cable.
ok got that will do this at weekend as the job that has bin done on this is bad all connector blocks and joins will run new wire and solder the joins.will let you know the result.
thanks softouch all went well and now have brake cut out.no more spare pants for me.
Welcome. Your resume button should work now also.