Troubleshooting Cruise Control

[rollinstone]

I've checked the circuit breaker, pulled the R/H and L/H switch buttons and checked the wiring, looked at the linkage under the hood, and still the "Set" button, when pushed, just causes the "Speed Control" light to blink, but not engage.

What about the brake cutoff switch? What can I check on it? Does it have an adjustment?

Thanks, y'all!

 

[Glacier991]

The brake on/off (boo) switch is roughly checked by just looking at the tail lights... but a more in depth check can be accomplished with a scanner.

 

[ASmallwood]

Cruise Control Trouble Shoot.

Your Symtoms sound very similar to what I went through last year. Mine was the brake shut off switch on the Master Cylinder. I unplugged the wiring harness from the Switch and used a paper clip to complete the circuit (bent the paper clip so it would fit into both ports on the wiring harness connector). I then took it for a test drive and the CC worked fine, so I got the switch from the Dealership the next day (I think it was like $10) and have not had a problem since.

Good Luck.

 

[rollinstone]

OK, ASmallwood...I tried your test and it worked! So I guess I have a bad shut off switch. Off to buy a new switch tomorrow and hopefully put this nagging problem to bed! Thanks!!

r.s.

 

[rollinstone]

BTW...how does that switch, officially called the "disengagement" switch, come off? It looks like an open-end wrench will do the job. If so, is there any problem with losing brake fluid? I would suspect there's a one-way valve to prevent fluid loss when the switch is removed. Please advise.

 

[ASmallwood]

I don't remember exactly, but I am pretty sure I used an open end wrench and I don't think much fluid if any came out, as I know I didn't bleed the system. I would just be prepared as you pull the old one out to stuff the new one in.

 

[rollinstone]

OK...we're going to install it tonight. Darn thing cost me $28 bucks at the Ford dealership! I called a couple of parts stores, but they said it's not an after market item.

I'm expecting a little fluid to come out, but it shouldn't syphon. Will make a quick switch of the switch!

 

[Glacier991]

Rollinstone what year Ex are you driving? I was looking in the CD manual and doggone if the Cruise Control on the 98 at least doesn't have a self test feature that will pinpoint the defective component for ya! (learn something every day around here).

 

[rollinstone]

Glacier...I've got a '97 XLT, 5.0L. I don't think the '97 has a self test feature. Wasn't there an overall model upgrade in 1998? At least there's nothing in my Chilton's manual that mentions it. What does your manual say? Maybe I've got something I don't know I have.

I'm still not 100% sure that my Master Cylinder disengagement sw is the problem. I did a resistance test on the exsting sw and the new one and got the same reading. I plugged into the new sw w/o actually attaching it to the mast cyl, and the CC engaged on a test drive, but the CC still won't engage the connector is plugged into the old attached sw.

Don't get it! I don't want to hook up the new one, yet, until I'm confident that's the problem. If I hook it up and the system still doesn't engage, then I just bought a $28 paper weight...actually, not a bad price as paper weights go, but I already have several.

 

[Glacier991]

Here's the stuff on the self test - yes a 97 will do this


Self-Test Diagnostics

WARNING:
THIS TEST IS A KEY ON ENGINE OFF (KOEO) TEST ONLY THAT IS CONDUCTED IN PARK ONLY WITH EMERGENCY BRAKE FULLY ENGAGED.

l Enter Self-Test Diagnostics by depressing the speed control OFF switch while turning the ignition key ON, ensuring engine DOES NOT start and is not running. The speed control indicator lamp on the intrument panel will flash ONCE to indicate that speed control module entered the diagnostic mode. Release the OFF switch.

l Note:
If the ON switch is not pressed within 5 seconds after entering diagnostic mode, the module times out and the procedure must be started over.

Press the remaining switches in this sequence: ON, RESUME (RSM), COAST (CST), and SET/ACCEL

l The speed control indicator lamp will flash as each switch is pressed. Press each switch in the sequence immediately after the light goes out for the previous switch.

l After all five speed control switches complete the sequence, the indicator lamp will flash to indicate a Pass or Fail:

— 1 Flash - Test passed.

— 2 Flashes - BOO switch defective, circuit defective, or brake pedal applied.

— 3 Flashes - Brake deactivation switch is open or circuit defective.

— 4 Flashes - Vehicle speed sensor is out of range or not connected.

— 5 Flashes - Speed control servo is defective.

l Immediately after the passed STATIC test, the speed control module then performs a DYNAMIC test automatically by actuating the throttle lever from 1mm to 10mm of travel from the idle position. During the DYNAMIC throttle pull, observe throttle movement to witness any binding or sticking of actuator cable, proper connection of actuator cable to throttle lever, and ensure THROTTLE RETURNS BACK TO IDLE POSITION. If improper connection and/or binding or sticking of actuator is observed, go to Symptom Chart.

Return Ignition Switch to the OFF position and proceed to the following Symptom Chart, if necessary.


Symptom Chart


Condition(s):

o Speed Control Inoperative

o Set Speed Fluctuates

o Speed Control Does Not Disengage When Brakes Are Applied

Possible Source(s):
§ Brake ON/OFF (BOO) switch.
§ Clutch pedal position (CPP) switch.
§ Speed control servo.
§ Fuse.
§ Circuitry.
§ Deactivator switch.
§ Speed control actuator cable.

Action(s) to take:
§ GO to «Pinpoint Test C».

o Speed Control Does Not Disengage When Clutch Is Applied

o COAST Switch Inoperative

o SET/ACCEL Switch Inoperative

o Resume Switch Inoperative

o OFF Switch Inoperative

o Speed Control Indicator Lamp Always On

o Speed Control Indicator Inoperative

 

[rollinstone]

Glacier...thanks for the self-diagnostic. It was very helpful. I applied the test and the system checked out ok! That's why my multimeter was indicating that the old master cylinder deactivator switch was good, but for some reason not working to allow the CC to engage when the "set" button was pressed.

So what was my alternative at this point? I did the only thing any good mechanic would do...I took out the old switch and WHACKED it a couple of times on my workbench, reinstalled it, and now it works fine!

Again, thanks for your help!! Without that diagnostic test, I'd have been forced to put on the new $28 switch. I'm sure it would have worked just fine, but I would have replaced a switch that just needed a little coaxing.