I went out this evening for a bit of a ride, top down, with my sweetie and noticed that the speedo was registering '0'. Stopped for an ice cream, stayed for about 40 minutes and started the old girl up and the speedometer was working fine. What's going on? Do these instruments quit and then fix themselves? If any of you have experienced this problem, please advise.
Just another day in the life of an XJS owner.
Cheers, RagJag

 

RagJag,

Apart from wiring etc, there's only 3 real components in the speedo circuit:

- the sensor mounted in the rear diff
- the speed interface module in the boot
- the speedo

As the speed interface module sends a signal which is sent to both the trip computer and the speedo, if the speedo reads nothing or inaccurately but the trip computer increments normally, then the problem is almost definitely in the speedo. Check the wiring connection and particularly the earth terminal on the instrument pack.

If the trip computer distance recording is also failing then teh fault lies further back in either the interface module or the sensor.

Hope that helps

Paul