Cruise Control Not Engaging Anymore

[duke16]

For some reason I can no longer engage my cruise control. I press the on button, and then set speed, but the light in the dash doesn't come on and the cruise control doesn't take over the throttle. Does anyone have any ideas?

 

[Turdle]

Disconnect the brake cutoff switch-on the master cylinder ( plug points up)
Look to see if you have a red plastic switch.
If you leave it disconnected- and try the cruise control again, it may work.
If it does, it indicates the switch is bad. Be careful though-your brakes will not turn it off, you will need to use the steering wheel off switch. Be sure to let us know what you find.

 

[dogfriend]

Some info in this thread:

http://www.explorerforum.com/forums/showthread.php?t=168572&highlight=cruise+control

 

[duke16]

Disconnect the brake cutoff switch-on the master cylinder ( plug points up)
Look to see if you have a red plastic switch.
If you leave it disconnected- and try the cruise control again, it may work.
If it does, it indicates the switch is bad. Be careful though-your brakes will not turn it off, you will need to use the steering wheel off switch. Be sure to let us know what you find.

Where abouts is the switch?

 

[Turdle]

Where abouts is the switch?

It is on the brakes master cylinder--sticking up

 

[duke16]

Well I unplugged the switch and still had the same problem. I also checked the fuse (#10) and that was fine.

 

[dogfriend]

Try running the diagnostic test here:

http://www.explorerforum.com/forums/showpost.php?p=1490028&postcount=11

 

[budwich]

I don't think unpluggin the switch at the master cylinder is the right "solution". If you do that, the system thinks you got your brakes on and therefore you "ain't cruisin''"... You need to unplug at the switch and measure it to see if there is a short or open. If it is shorted, then its ok, if its open, then you have a problem.

 

[dogfriend]

If it is shorted, then its ok, if its open, then you have a problem.

Are you sure? I thought that they shorted when they go bad. In normal operation, they should be open unless you are stepping hard on the brake, which closes the circuit.

 

[Turdle]

Are you sure? I thought that they shorted when they go bad. In normal operation, they should be open unless you are stepping hard on the brake, which closes the circuit.

I thought so also, until right now

I connected my meter--sure enough normally closed---

Opens upon depressing pedal---hummm

Learn something every day

Thanks Budwich---


This means current is applied all the time--remember the recall?
A fuse in line is a good idea--

 

[dogfriend]

I thought so also, until right now

I connected my meter--sure enough normally closed---

Opens upon depressing pedal---hummm

Learn something every day

Thanks Budwich---


This means current is applied all the time--remember the recall?
A fuse in line is a good idea--

Now I don't understand how they fail.

I read the NTHSA report and I thought that they failed when the brake fluid caused corrosion and the corrosion products shorted out the switch.

Now I'll have to reread it again.

 

[budwich]

Let's not get the recall mixed in with why the cruise doesn't work. The circuit is quite specific (at least in 96 drawings). The recall if I understand has to do with fluid leaking thru the membrane which may cause a short .... but to ground. The circuit "normally" passes the voltage to the speed controller not to ground which would be a problem ... hence the recall.... very basic understanding, there is probably a lot more to it than that. As for you cruise control not working, now you know that it is unlikely the switch. So now you can look elsewhere. The next most likely cause is the BOO switch. Check it next.

 

[budwich]

One other thing to check since you checked the pressure switch is to check for voltage (with a volt meter) that it is indeed coming into the switch when your key is on.

 

[gijoecam]

Indeed, the switch in question is a normally closed switch that opens with more than 200psi on the system. The problem, if you had read all 60-some pages of the report, is that the circuit can short to ground when the membrane fails and the switch fills with fluid. Under normal operating conditions, the switch is closed and sends power to the speed control servo.

Now, even if that switch was jumpered-out, the primary method for deactivating the cruise control is still the BOO switch on the brake pedal. The LG wire feeds the speed control servo when the brake pedal is depressed. That 12V signal from the BOO switch is supposed to cancel the cruise. The pressure switch is a redundant backup for it, should the BOO switch fail (which isn't uncommon).

Now, as for the problem at hand, it could be a number of different things. There is a whole diagnostic procedure in the manual, but the first thing to check is the fuses. Unfortunately I don't have the 97 schematics in front of me, so I'm not going to quote fuses and amperages just yet, but I'll see what I can dig up in the morning.

Also, don't be too quick to assume it's the switch. The actual number that have failed in Explorers is remarkably low.

-Joe

 

[duke16]

Sorry guys, for some reason I stopped receiving Topic Notification Reply emails for this thread.

I took my airbag out today to diagnose that, and it turns out my clockspring is broken. So that would explain my airbag and cruise control not working. And, as it turns out, my horn doesn't work either. So I just need to find a new clockspring. Thanks for the suggestions though.
http://www.explorerforum.com/forums/showthread.php?p=1554520