Cruise control not working. Anyone have any diagnostic help?

[BlackFox5.0]

I don't even know where to start first. I have soe shop manuals and will look at the when I get home, but figured I would asked, because maybe the fix is soemthing common. As far as I know no fuses are blown. The car is a '90 LX, was auto but now 5-spd. The cruise did not work when I got the car with the stock AOD.

 

[Pyro]

I've heard a common cause of this is a busted switch. My CC is busted right now too. It used to work when I pushed the buttons down really hard but no longer. I've been meaning to fix this for a while, just never got around to it.

 

[rd]

Couple of simple things I can think of.

There should be a vacuum dump switch on the brake pedal, (maybe clutch also) so that anytime you hit the brake, it dumps the vacuum from the cruise. It is a normally open switch (I think) that closes when the brake pedal is in the up position. It is also adjustable, and if it gets out of adjustment, ie, stays open, cruise will not set.

Make sure the speedo sensor and speedometer cables are working.

Next is checking the electronics. This takes a wiring diagram, most likely from a Ford Shop manual, but can be done. You can disconnect the steering wheel switches and check them with an ohm meter, as they send all their signals via two wires, but the different functions have different resistors, so there is a different signal to the box for each function.

If your car still has the electronics in a small black plastic box under the dash by the steering wheel, find one in a junk yard and swap, I have found them to be interchangeble for Fords, Mercs, etc, from about 76 to at least 85.

 

[BlackFox5.0]

Thanks rd, I have my '87 still which had cruise so I have parts from that for the time being. I also wondered what that rubber hose was on the brake pedal. I thought it was for the brakelights somehow lol. Anyways, I assume this switch should be pushed in at all times, so when you step on the brake it comes out? i had to chane the pedal assebly and had to move that hose, but I think I put it back so it owuld work properly (remember now, I thought it had something to do with the brakelights, which I had trouble with in the past, thats fixed however.)

My VSS and speedometer work, if they didn't my car would stall upon stopping, and I wouldn't be able to see how fast I was going without a working cable obviously.

Oh yes, all the vacuum lines are still connected as I checked when I had the fender apart.