Hi Jag-Lovers,
Looking for some help if poss.
Need the Location of the Magnetic Speed Sensor and Control Unit for the Cruise Control.
A photo would be great.
Thanks in advance,
Bruce
On a 84 the transducer should be on the transmision, left side if I remember correctly. If not there then it would be at the rear of the differential.
Don’t know about the XJS but on the saloon and LHD the CC Control Unit is on the passenger’s side footwell.
Speedo transducer is on the left side at the very end of transmission where it mates to the output shaft tunnel. I believe it didn’t move to the differential until 1989 ?
Right side near front of transmission is where the vacuum modulator is that controls shift points.
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Given the variables of model year designations your '84 might still have a cable driven speedometer. If that’s the case then the speed pick-up for the cruise control is at the end of the driveshaft, very close to the differential. So, if you don’t find a transmission mounted transducer, look further aft 
FTR:
That change was made at VIN 142xxx (or 144xxx? Something like that) which was during 1987 calendar year
Cheers
DD
Thank you Aristides and Doug,
I did not realise that the Speedo and Cruise shared the Transducer, my Transducer is indeed on the T400 Trans. Brake Lights work, Speedo works, I have bypassed the the Blue safety cut off Solenoid and connected vacuum directly to the bellows, with Engine running and applying 12 volts at the Bellows unit it operates correctly.
I have checked the fuses and all are OK.
Cruise Control still not operating, any Ideas welcome.
What colour is the Control Unit and what does it look like would be a great help.
Cheers,
Bruce
This may help
https://www.jag-lovers.org/books/xj-s/16-Cruise.html
The module/control unit looks like this
Cheers
DD
If the Speedo works then the problem is elsewhere.
Test also the Set button at the stalk switch.
Does the CC master switch has power?
Note that the CC will not work below ~ 40 km/h
Thanks Doug for the Photo,
Good question Aristides, I will check for power at the Master Switch, will check the Set button also,
Thank you both for your help.
Bruce
Aristides,
Have checked master switch, and yes have 12.3 volts, switch seems to be OK.
Is there an easy way to check the stalk set button for correct operation. ?
Regards,
Bruce
Easiest would be at the CC module plug, one of the cables should connect to earth when you press the Set button.
Aristides, Found correct cable to set button and when pushed goes to earth correctly, I have a horrible feeling my CC module may be faulty ?
Bruce
If the solenoids checked ok, the below is not leaking and the unit gets power and speed signal, then it’s the last item on the list.
Verify that the cruise control microswitch on the shifter is adjusted correctly. It has to be engaged when the shifter is in drive. Mine fell out of adjustment and a slight movement of the shifter when driving would not allow it to close rendering cruise inoperative.
Follow the checkout procedure for the cruise control in Kirby Palm’s book. I made up one of the test circuits made of bulbs and resistors described in the book. However, use 5 watt or higher resistors, or the resistors will smoke!
Very good point Jon.
Thanks Gents, I am onto it.
Bruce