help diagnosing cruise control

[verlane24]

Let me give you guys a little history. While grinding out rivets to replace the radius arm bushings in my 93 xlt, I slipped and sliced my clutch line. After replacing this, my cruise control does not function. Here's all I can think of that I messed with that may have caused problem.

First, being the over zealous dumba** that I am, I removed the brake pedal by mistake instead of the clutch pedal. I believe I replaced it and the BOO switch correctly since the brake lights work OK.

I removed the clutch pedal and the master cylinder to replace the line, and in the process unpluged the white connector under the hood that looks like it comes from under the dash to the cruise unit. I verfied that it is plugged in, and I have also checked the vaccum line that goes to the vaccum tree and it appears to be snug and not leaking.

After finally figuring out that the only way to get that b**ch back in there with the hydraulic line attached was through the wheel well, I reinstalled the master cylinder, the clutch interlock sensor and the clutch pedal. I broke the snap ring while taking the pedal off, so I used a zip tie in it's place, and the pedal feels snug with no lateral movement. The clutch interlock sensor will only go in one way, and the truck will not start with the pedal released so I am assuming it's ok too.(Maybe not).

The only other thing I can think of is a blown fuse, but since I haven't an owners manual I haven't checked it. I was also under the belief that the cruise and the horn were on the same fuse and the horn works fine.

What am missing? Is it possible for the BOO and the clutch interlock switch to partially work, but send a bad signal to the cruise? Could I have somehow not installed the master cylinder correctly, messing up the interlock sensor? Am I incorrect in thinking the cruise and the horn are on the same fuse?(going to check haynes at lunch today) The battery was disconnected during all of this, so I don't think I shorted anything out. The cruise worked perfectly before this repair. How should I go about diagnosing this problem?

Thanks in advance for the help!
Brian

 

[Robb]

Does yours have the "pressure" switch at the end of the master cylinder? (round thing with a two-wire, red harness plug) Check to see that you have continuity across the two terminals of the switch, while everything is off. For some reason, I have had two of those things go bad recently.

Yes, the CC fuse is the same as the horn fuse. If memory serves, it also uses another circuit also with a different fuse. I will have to look that up though.

 

[verlane24]

Are you talking about the cylinder thingy that slides over the clutch pedal and snaps on the master cylinder where it comes through the firewall? I "think" that's called the clutch interlock switch, or something like that. I was under the impression that the truck wouldn't start with pedal pushed in, or would start w/o the pedal pushed in if it were bad. I can't remember how many wires it had coming off it... if you are referring to something in addition to that, I'm pretty sure I don't have one. I will definately check it out thanks! You're saying I should have continuity on the switch itself with the pedal released right?

 

[verlane24]

Robb,

Just checked under the dash and all I see is the interlock switch, and it has 5 wires coming off the harness. Am I supposed to have something else under there?

 

[Robb]

The switch I was reffering to is the Deactivator Switch, on the end of the Macter Cylinder.(the red thing in the pic below)

How many pins do you have in the harness on the actual servo/actuator under the hood? I may have the documentation at home to "pin test" the harness to find out exactly what is not working. If you have a multi-meter, I could probably scan the information tonight.

 

[verlane24]

Ooops, my bad. I don't think I explained myself very well... I never removed the brake master cylinder, just the brake pedal. I took the clutch master out but didn't mess with with brake master. And mine doesn't have that red thing anyway, just the connector towards the back pass side of the brake master cylinder. In ref to the number of pins, are you talking about the wiring that runs from the fire wall to the cc unit? I don't know the exact terms for all that stuff....

Thanks for the help!
Brian

 

[verlane24]

The wire to the cc servo has 6 pins. I checked the vaccum lines again, as well as the fuses and all seems well.....

If you could locate somethig that would let me diagnose this sucker with a multimeter that would be awesome...

Does anyone know a procedure for verifying function of the interlock switch and/or the BOO switch?

thanks
brian

 

[verlane24]

BUMP

Anyone have any ideas?

 

[verlane24]

BUMP

No one knows anything about CC?

 

[MrShorty]

I don't know the answer to your problem, but I'll tell you what I would do next. I would go to the library and see if I could get a hold of a professional service manual (Mitchell, Motor or equivalent. usually in reference section). They will have a section called "speed control systems" that will describe the system, give wiring diagrams, troubleshooting charts, and such. It's been a while since I've had to look up cruise control servicing, so I can't remember any specifics.
One thought I just had, since you removed the brake pedal, I wonder if the "dump" valve got goofed up. There's a valve attached to the brake pedal (again I don't remember the specifics of where or how) that open when the brake pedal is pressed to "dump" the vacuum (Cruise control uses engine vacuum). (This valve is in addition to the electrical BOO switch.) Maybe this valve isn't closing now, so the cruise control servo doesn't have vacuum. ALso, since it hasn't been mentioned, make sure the vacuum lines from the manifold to the servo are still intact.

 

[verlane24]

Thanks, I'll look into the "dump valve". I really feel like it has to be due to something I messed with since it worked fine before. I have verified vaccuum from the manifold to the servo. I guess a trip to the library is in order.

Let me know if anyone thinks of anything else.

brian

 

[ed d]

cruise control prob

when i was replacing injectors and fuel pressure reg. on my old '92, i needed to remove the intake plennum, thus the vacuum hoses needed to be removed from the ports. Trace the vacuum lines from the cruise control vacuum canister, and there should be a round black and white plastic thing in one of the hoses. i'm not really sure off hand which side goes which way, (ie black forward, or white fwd) but try turning it around. when i reinstalled everything, i installed that thing, (i think it's similar to a check valve,) backwards, and the cruise wouldn't work. I stopped on the highway one day and switched it around and it worked. Good luck.

 

[410Fortune]

I didnt read the whole post but there is a vacuum switch at the top of your brake pedal, seperate from the BOO circuit. This little vacuum plug is strictly for the cruise control canister. Make sure it is adjusted properly.....

 

[verlane24]

ed d - the only thing on mine like that is a blue and white dealy that is connected the the cc canister on one side, and to the vaccum hose to the plenum on the other. I didn't mess with it any, so I doubt that's the problem, but I'll check it out anyway.

410- So there is another switch on the brake pedal? Is it on the firewall behind the pedal or on the pedal itself?

Thanks again
Brian

 

[410Fortune]

on the top of the pedal.
it is adjustable

There is a white plastic attachment on the pedal that this button presses against.

The button should be out with the pedal in the rest position, I believe. You may want to look at a friends truck, or I can go look at mine.

If its not adjusted right it wont work.

The vacuum line from the cruise canister that goes through the firewall goes to this switch.....

 

[verlane24]

UPDATE FIXED

You were right 410....

There is a plunger button that faces the floor under the dash. There is a plastic "shelf" thingy that is attached to the brake pedal that pushes the button in when the brake pedal is released. Mine was loose and not engaging the button all the way. So I put about 10 of those 3m sticky pads on top of the plastic do hicky so it pushes the button in completely when the pedal is released, and that fixed the problem.

The button is hard to see since the plastic thing covers it, but if you are having cruise problems you should check it. It's not "easy" to get too, but I was able to reach under the dash and engage the button while driving to verfiy that was the problem.

Anyway, just wanted to update the thread for future readers....

Thanks for the help guys!
Brian

 

[Claus]

Cuise Control Fixed

I had a non-working cruise control as well on my 2003 Ford Explorer. Thanks to mostly your help I determined that it was the speed control deactivator switch (with stability assist). This switch is a pressure switch that senses the pressure of the break fluid and is located by the break fuid reservoir as shown by Robb's picture in this thread.

I used an ohm meter to test the switch which, according to the work shop manual should have less than 5 ohms with the break pedal released and more than 10,000 ohms when the break pedal is pressed. My measurements of the non-applied breaks where above 5 ohms somewhere in the range of 200 to 45 ohms. One could notice how slowly the resistance was reduced after the break pedal was released. However the resistance didn't seem to get near or below the required 5 ohms. In layman's terms this means the pressure switch never closes completely, allowing the cruise control to function.

To double check my testing results and to verify that is was the problem I used the paper-clip test mentioned several times thoughout the forum. I shortened the paper-clip to make a simple U and hammered the ends a little flat since the switch contacts are flat as well. This made it easier to insert the paper-clip into the plug and doesn't strech out the contacts as much. Be sure to put electrical tape around the paper-clip and plug to avoid shortening that might occur should the paper-clip touch a metal part. Also tape it to something so it doesn't hang around to badly. The cruise control worked perfectly during the test drive.

Do realize, however, that with the paper-clip test you are circumventing a safety switch that disables the cruise control when the break is applied. If I'm correct the break light switch on the break pedal is also used to disengage the cruise control. Both are used for safety reasons. So please don't get the crazy idea to drive around with a paper clip instead.

I purchased the speed control deactivator switch (with stability assist) from the local dealership of the next town for $26.64 (incl. tax). The parts & service department of the dealer here in town is closed on Saturday ... sucks! Part number is 3L3Z*9F924*AB but the parts departement should be able to find it without that number. Installation was simple. I placed a couple of rags below and a cut-off cub to catch any break fluid. Then I used a 7/8 open socket wrench to remove the old one and attach the new one. Be sure not to overtighten it since you have a huge leverage with that large of a wrench. At the old switch is removed a little break fluid will be pushed up and out of the opening but if you are attaching the new one right away not much will be coming out. After you are done wipe everything clean, apply the breaks a few times and check for leaks. Check for leaks again after your test drive.

Thanks for all the help that was posted before I needed it. Maybe this post will help others as well.

 

[Claus]

Oh, totally forgot to ask. What is the "stability assist" that's mentioned with the speed control deactivator switch?

 

[brockli01]

The stability assist has yaw sensor that can tell how much the vehicle is shifting on turns or evasive maneuvers. This works in conjuction with the abs, if the explorer is shifting too much weight to one side, it will use the abs to apply the brakes to stabilize the vehicle. All to keep the explorer from ending up on its roof. The 3rd gen's that have stability assist will have a wheel speed sensor at each rear hub(wires clipped to the rear brake hoses feeding the calipers). While the standard setup has one speed sensor on the top of the differential.