Trouble shooting cruise control?

Hi. Since I bought my 99 xj the cruise control hasn't worked. The light doesn't come on in the cluster and the cruise control will not set. Despite some effort I haven't found much information on how the cruise control system works so all I've done so far to trouble shoot is checking all the fuses (all good) and checking for vacuum leaks (none). Any advise on what else to look for?

Clock spring.

If the light does not come on there is most likely a fuse or switch problem. You should inspect/clean the wire plug at the cruise module under the hood. Typically a clock spring problem would light the airbag light on the dash, and/or cause the horn to not function.

Could also be a bad switch, the switches communicate to the PCM with specific resistive values, given there are only two wires and 5 switch functions. Is everything factory?

I sent you a PM

The cruise control on my '98 XJ was intermittent, sometimes it'd work sometimes it wouldn't. Then the dash cluster became intermittent. Took the gauge cluster out and cleaned the terminals. Put it all back together and the cruise control worked fine, until the neutral safety switch started going out.....

I have the same problem with my '98. The light comes on but the cruise still doesn't work. It's been like that since I got it about a year ago. I think my NSS may have something to do with it.

I was having an issue where it wouldn't start, so I took the NSS out and cleaned it. It was better but not right, so I got a junkyard NSS and cleaned it up, then put it in. Now it starts every time, but only in park. It still won't start in neutral. Plus the cruise still doesn't work.

I'll get another JY one and see if it's any better. It seems like that might be my problem. Have you fixed yours yet diggerdave?

Sounds like yours might be more of a vaccum leak. Since the light is coming on in the dash I'm guessing that means the cruise control module is being powered. But with out proper vaccum pressure (suction) the cruise won't work. Have you noticed if your climate control won't stay in the zone you put it in or is always blowing out of the defrost vents? If so you defiantly have a leak.

Most common places I've found for a vaccum leak is at the ball canister in the bumper, the hoses right by the fuse box and A/C dryer, and the tiny hose that goes through the firewall to the climate control box. (Located right under where the A/C lines go through the firewall)

Well after messing with mine off and on, I finally fixed it. I had seen where someone else took the cover off of the cruise on/off, set button on the left side of the steering wheel and cleaned out some gunk and that made theirs work. So I popped it off and everything was clean. However, I did notice 2 cracks inside of the button. When I would push set, the cracked bracing would never allow the button to be fully depressed. I put a little super glue on the cracks and it works like a charm. I do have another button that I'll put in, but this works for now.

Maybe you'll get lucky and something like this could be your problem? Good luck.

On mine, the cruise will work for a couple of miles and then gets weak, won't cause a downshift to go up hills, etc. The light remains on. I am suspecting the actuator. Is there a good way to check it?

I think the downshift is also a function of vacuum. On my XJ the cruise doesn't like to downshift with larger tires. I guess the lower engine rpms caused by larger tires prevent it from creating enough vacuum?