Cruise Control Does not Shut Off

[daddy-justin]

My 1988 Ranger has a small issue. When I step on the brakes to disengage the cruise control, everything seems fine. when I release the brakes, the cruise control reengages. The only way I can turn off the cruise control is to hit the Off switch on the steering wheel.

Truck is 1988 Ranger and CC is factory installed. Any ideas would be great.

I did a lot of research and I do not see anyone with a similar problem. I did find this part that sounds like it might solve the problem.

http://www.partsgeek.com/catalog/1988/ford/ranger/body_electrical/cruise_control_release_switch.html

Any thoughts! Thanks in advance.

Justin

 

[RonD]

Do your Brake lights work?

Brake pedal cuts off cruise control in two ways.
The Vacuum module(speed control servo) in the engine bay that actually pulls the throttle open has a vacuum hose that runs inside the cab to the brake booster/brake pedal push rod.
When you press on the brakes that vacuum hose is opened releasing pressure so "servo" releases throttle, but this doesn't turn off Cruise, it just releases vacuum pressure, as soon as foot is off the brake pedal vacuum pressure would build back up and "servo" would pull on throttle again.

So it reads like your problem is electrical, Cruise Amplifier (the brains) is not getting the Brake Pedal electrical signal, or is ignoring it.

Automatic and manual trans both use "clutch pedal wiring" to send brake light signal to the Cruise amplifier.
When you press brake pedal 12volts goes to tail lights but also thru the Clutch switch wiring to the Cruise to signal amplifier to cut off cruise.

On a manual pushing in the clutch also needs to turn off the cruise control, so wiring is based on having a clutch pedal cut off, if an automatic there is just a jumper inserted in place of the clutch switch.

Your link looks like a Clutch switch, not sure if 1988 used one of these on the brake pedal for cruise cut off.
And no need for it since brake light switch has to be there for brake lights to work

here are the two diagrams for cruise
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Cruisecontrol_1of2.JPG
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Cruisecontrol_2of2.JPG

It reads like your cruise amplifier is not getting the "brakes are on" electrical message

 

[adsm08]

On my 88 I had the same issue. What I found was that the vacuum dump switch doesn't always shut it down, and neither does the clutch switch.

My issue was that the brake switch was not working (I think it may have fallen off). If I hit the brakes, even hard, it would accelerate again after I let go of them, and if I hit the clutch the engine would just rev up. The only way I had to shut it down was the off button on the steering wheel.

 

[RonD]

Vacuum hose being open should stop servo from pulling on throttle but won't shut off Cruise, it is just a mechanical valve no electrical parts.

The brake or, if manual, clutch switch should turn off current speed setting but won't shut off Cruise itself, you should need to set speed again after pressing brake or clutch pedal.

 

[daddy-justin]

Brake Lights Are Not Working

Thank you very much for the replies. The brake lights are not working.

I will check this out tomorrow.

 

[RonD]

Then check the fuse first, cab fuse panel, and then the switch.

Brake switch should have 12 volts on one terminal all the time, key on/off doesn't matter.
When brake pedal is pressed the other terminal should now show 12volts

If fuse is blown, and then blows again with new one, check trailer light wiring first, these wires get alot of water sprayed on them and can corrode a short out

 

[daddy-justin]

All Fixed

Thank you very much for all the help and pointing me in the right direction. The wires were kicked off of the brake switch. All is well. Thanks again.

Justin

 

[bobbywalter]

yeah...on those it has the floater style brake switch. make sure the wrap tab is not broke or it will try to buck the pigtail off again....i went to electric gm cruise control to shitcan the vacuum issues.

 

[AllanD]

I feel I must note at this time that if the Brake light switch or the brake lights are disconnected (or even both brake lamp filaments burned out) that EEC4 will fail it's own
self test... the self test circuitry is grounded through the brake light switch and then to the brake lamps...

And in this mode the system goes to rich mixture by default!