I badly need to fix the cruise control on this car. It runs so easily at highway speed I have to constantly raise my foot off the gas pedal. I got a speeding ticket Sunday for 67 in a 55 zone. First speeding ticket in 37 years.
I remember that aftermarket cruise controls could be gotten but now I don't see them.
600 mile trip this last weekend with no problems and no oil usage. Pleased, to say the least.
Thank you for any thoughts, RagJag

 

Check the cruise control bellows. Is it torn, punctured?

#21 in the attached picture.

 

+1, very common problem. Also make sure that the vacuum hose is connected securely to the bellows and the pump.

If good there, check the the connectors on the pump and dump valve.

Then I would check the cruise control module which is under the cover in front of the passenger seat. make sure all the connections are clean and tight, including the ground.
Check that you have 12v on pin 1 when ignition is on.
Check resistance on pin 17, it should be open circuit when the CC switch is off, 100 ohms when 'set' is pressed and 300 ohms when 'resume' is pressed. If not then pull the switch from the center console and check it.

You can download the electrical guide from the 'How to" section at the top of this forum.

Cheers,

Allan

 

https://www.jaguarforums.com/forum/x...celift-101308/

Allan,

He has a 96 like mine. The cruise control module may be over the rear driver's side wheel well.

I know its strange, and my service manual doesn't acknowledge that location, but that's where his may be as well. It'll definitely be easier for him to get to!

 

Oops, sorry about that, I had my 94 electrical guide open and not the 96. The 96 guide does indeed say that it is over the left rear wheel arch. The tests for inputs are the same though.

Thanks for putting me straight Vee

Cheers,

Allan

 

Thanks Vee and Alan. I will try the tests you said. Yes, Vee the bellows is good. The vacuum pump is on the left fender well. I don't know if it is getting 12 volt or vacuum from the system. I do have the '96 electrical guide and that will help.
Cheers, RagJag

 

My cruise control module failed. It is on passengers side foot well under the carpet and cover plate in front of the seat. Foot well had filled with water at some time. $20 on eBay. This was after confirming that sucking on the bellows worked and that the vacuum pump created a vacuum and tat the vacuum dump valve did not have a leak. Dump valve and pump are tough to get to and sort of behind the overflow tank on front left engine bay.

 

So I just found out that my cruise control isn't working!

I do have 12V on Pin 1, and I can get to 500 ohms when pressing resume. I also get to 108 ohms when pressing set, however I don't get anything when selecting the cruise switch to on. (I was getting 50 ohms initially, but I don't get it anymore)

Seems like the switch, no?

 

Well, Vee the cruise control has too many things that will keep it from working if any of them are not right. Module, gear shift switch, transmission module, console switch, resume switch, vacuum pump, and actuator bellows are most of them.
In testing yesterday, pin #1 had 12V if ignition is on. Pin 17 had 100 ohms resistance when 'set' but I got nothing on the resume button. I don't have any step by step instruction on this thing.
RagJag

 

Vee,

I don't know that you would see a particular resistance on pin 17 when the switch is in the ON position?

Check output voltages on Pin 10 and pin 3 of the CCM when the switch is set to ON the signal goes to ground on pin 10 and 12v on pin 3, when off it goes the opposite. If it does your switch should be good.

Cheers,

Allan

 

Switch is good.

Dammit. I was hoping for something simple. I don't think I'm going to bother checking since I so rarely ever need or want to use it.

Maybe someday...

 

OK,

I got the vacuum pump to make a click sound when I fed it 12v of power.

I could not get the dump valve to make any sound with 12v of power.

I'm going to assume it's the dump valve. I took it off, cleaned whatever I could clean and put it back on with no change in results.

If anyone knows how to diagnose a the dump valve, I'd appreciate it. It seems like it would be easiest to find the problem if I could check things while the car was moving above 30MPH, or whatever speed needed to activate the cruise control.

Thanks for the continued help.

 

Vee,

The valve should be getting 12v when the system is inactive, check the PM5 connector at the valve to make sure it's there and the connection to ground is good. The wiring diagram shows states that the valve closes when approx 0.5v is applied. So if you have a variable power supply, apply 0.5v to the valve and then using a hand vacuum pump apply vacuum to the valve. The vacuum should hold steady. If you switch the input to 12v the valve should release the vacuum.

If that works, you said that you heard the vacuum pump make a noise when you applied power, did you check to see if it is actually generating vacuum? Stick a gauge on it to check.

Cheers,

Allan

 

Great info like this should be in the 'sticky' sections. Thanks Allan!

 

Well, it wasn't the dump valve. I swapped it out with another one and I still don't have cruise.

I'm going to see if I can get what I need to diagnose the pump. If not, I'll see if I can get one without spending much.

 

My Cruise has never worked and will be replaced with a Rostra servo motor controlled unit for about $200. No more vacuum issues.

 

Warjon, does the Rostra unit replace the function of the cruise control module in our cars?
RagJag

 

Yes, there are a couple of models. Some use ODB speed input and some use separate VSS input, there are also models for electronic and mechanical throttle. This one has its own VSS input and is for mechanical throttle.

Here is the one I am looking at

Rostra 250 1223 Universal Cruise Control KIT W 250 3743 Right Side Handle Stalk | eBay

Rostra 250-1223 Universal Cruise Control System

 

Warrjon, the Rostra 250-1223 web site does not list Jaguar in the cars this unit will fit.
RagJag

 

It is a universal unit it will fit anything with a mechanical throttle. They probably don't list Jaguar as Jags came with cruise control from the late 70's.