cruise control not working 90' Renix

I checked the vacuum line to the canister and back to the servo. all fine. When I pull of the little line you can hear air coming in.
The plastic piece at the end of the cable is connected to the throttle. than a big line goes into the firewall (no idea where)
The cables at the level were broken and I repaired them.
Under the dash the cables go into a connector and in a yellow box.
What elese can I check or messure???
How can I check the brake switch or adjust it?

The big vacuum line that goes into the firewall goes to your brake pedal. It forces the CC to disengage if you touch the brake pedal. A fail-safe basically.

checked the HZ/stop fuse, it was bad. changed it. what does it is for?

My guess without looking at schematics is your brake lights / hazard lights?

But they worked with the bad fuse?!?

cruise on my '90 XJ wasn't working. found that their is a vacuum switch that touches the brake pedal and it had shifted back so that the cruise control thought I had stepped on the brake. pushed it fully forward and it works properly again.

I sprayed a little WD-40 on the seal around vacuum switch been workin ever since. bout 5 yrs.

At the upper end of the brake pedal arm where it is really hard to see, there is the brake switch. It is a combination electric and vacuum switch, this is what disconnects the cruise when you step on the brake. My Jeep had a break in the vacuum line going to the switch and so the cruise would never engage......

I tested the servo itself today. I diconnected the plug and put voltage to the orange wire and double ground to the both down in that plug. started the engine and the cruise servo directly started to open the throttle. I also checked the cables from the lever to the connection under the dashboard. all were fine. the white plastick thing at the brake paddle is also adjusted so that it is closed while the paddle is not pushed. I do not know what else to check???

Greets--Can not help you directly with a solution. However take notice of the bottom of the page where everyone, (everyone available at this time in space that is), replies to your present day question. There is a small section; SIMILAR THREADS. Therein you might explore the many posts. The deeper you go into the past references you will also find that the posts will change, i.e., go backwards following said posts, and you will see different ones engaged into the same similar issue(s).

I dislike the search box of this site, (and similar sites), as even if I use a basic term; brakes.., I will get results about most anything but brakes.., sheesh! As a quick alternative try 'googling' . Enter these words into the google box; cruise control+naxja.

As a side note, lol, the only cruise control I've ever used was a wedged shape rock, (about the size of an American football), and another time, an axe handle.

The vacuum line from the brake pedal switch is only to allow the brake to disrupt the vacuum and disengage cruise.

Trace the vacuum line from the brake pedal switch to the servo. remove the line from the servo and plug the servo port. that removes the vacuum portion of the switch from the circuit.

then try your cruise again. if it works, you know you have a vacuum leak in the line from the switch to the servo, only downside is that you cannot kill cruise with the brake, you will have to turn it off at the steering stalk.

my vacuum line was broken right at the switch and i fixed it with a piece of ball point pen barrel

today I changed:

complete cruise control wiring harness
brake switch (the white one)
turn signal lever

It is still not working !?!?!?

How can I check the brake switch? Can it cause the problem? what is with the speed signal thing that goes into the wiring? How can I check that?

Do you have the FSM? There are tests for the switches on the turn signal lever. My 91 CC has not worked for a decade because the wire inside the steering column is broken and I haven't had the chance to take the thing apart yet

I searched for some PDF files I can use to check my cruise control.

this is what I got:





The switch on the turn signal lever is ok...checked it as it is written. I can not check the speed signal that comes from this little plastic thing under the dash at the speedocable? what is this?

My 1989 xj is doing something similar now. The cable going from the throttle body into the firewall has a plastic piece with a spring inside it. The plastic broke and the spring has no tension so when I accelerate, it maintains whatever the highest rpm was. I can't find a name for this cable or a part number ANYWHERE!!!