Jaguar Repair: XJ6 - 1985 - speedometer pb, fuse panel, service interval

Question
QUESTION: Hi, my 1985 XJ6 speedometer started to go wrong randomly and then eventually stopped. Mileage isn't working too now. I removed the panel under the dashboard but couldn't figure out which is the right cable - can you help? Thanks.
Jérôme

ANSWER: Hi Jerome,
The 85 XJ-6 Jaguar does not have a cable driving the speedometer. It is electric and is powered by a pulse generator driven by the transmission. All you can do without some test equipment is to check for power on the green wire to the pulse generator. Also check the green wire to the speedometer and the connection of the yellow wire from the pulse generator. There are several other components in the system. The pulse generator also sends a signal to the service interval counter, cruse control, trip computer and the interface unit.
Howard

---------- FOLLOW-UP ----------

QUESTION: Howard,
I must be stupid but even with Haynes service manual I cannot figure ou how to access the back of the speedometer. If I remove the dashboard tray there are hoses and can't reach de speedo. If I go the other way, remove the fuse panel under the dash it's a bit better but cannot make it with a tester. I don't see any other way but to remove it. Can you help please? Thanks a lot.
Jérôme

Answer
Hi Jerome,
You will hate yourself on this one. To get the speedo out you just push in and turn the speedo and it will pop out. The tach comes out the same way. One of the very few easy jobs on the car.
Does your trip computer work and your cruise control? If they do your right to check the speedo but if they don't then you should check the pulse generator on the transmission first like I said earlier.
Howard