1990 Cherokee cruise control

[heavy equipment]

I'm having trouble with my cruise control - it quits intermittently. I suspect the speed sensor. I found it in the speedometer cable, but it looks different from the one on my '89. The '89 has a pancake shaped metal case and threaded connections to the cable on both ends. The one I see in my '90 is black plastic and I can't figure out how it connects to the cable. I don't want to break it - has anyone had to change one of these? How does it come apart?

Thanks for any suggestions!

[Muad'Dib]

Aren't these run off of vacuum? If so I would start there.

[heavy equipment]

The switch stalk is new. After I installed it and a light to let me know that the brake light switch is working the cruise control worked for a while and then quit. I know the servo unit is O.K. because when I push the slide switch to accel/resume it accelerates. When I press the "set" button, nothing happens. When I pull the vacuum supply hose off the servo unit I hear it sucking air, even if the Jeep's been sitting a few days (I built a big vacuum reservoir in order to have the A/C controls work when I'm pulling a travel trailer uphill).

I want to get the speed switch off to bench test it, but I can't figure out how to disconnect it from the speedo cable.

I'll check the brake switch/valve, but I've tried holding the pedal up with my foot on bumpy roads, and it didn't help.

[heavy equipment]

Well, I just found out that the gadget I thought was the speed sensor - isn't. It's a black plastic cylinder-shaped device that's spliced into a cable. I think it may be the safety interlock that won't allow the key to turn if the trans isn't in Park. I disabled that nuisance long ago. I found the speed sensor and it seems to test OK. I guess I'll try replacing the control box and see what happens.

I pulled out the vacuum dump/switch and it tests OK. It's adjusted right, too...

[heavy equipment]

Resolved - I found a connection unplugged at the brake switch, and the plug connection for the new switch assembly didn't plug in far enough until I slid the plastic insulator back a little.

[shawnxj]

i need to research why mines not working as well but i think it might be the harness in the column.......i need to check that brake switch to

[heavy equipment]

Check vacuum connections first - it's easy. Pull the hoses off the servo unit. One of them goes to the manifold or vacuum cannister, and the other one goes to the brake valve/switch. The one that goes to the vacuum source should suck air, at least when the engine is running. The one that goes to the brake valve you can test by clamping your lips around it and sucking. If you can get air through it that way, check the hose and the brake valve. You can pull the hose off the brake valve and push on another piece of hose and suck on that. If the first and second test both fail, the valve is either bad or maladjusted. If the first test fails and the second passes, find the leak in the hose.

[shawnxj]

thanks i'll look into that