Hello there Jamo,
We seem to see more and more from Autofurumz.com. Welcome to USENET.
Well let's see. There once was a time where cars used cables that were attached to the transmission and were routed to the back of the speedometer itself. Today optical transducers and proximity sensors have replaced the cable and are either attched to the rear of the transmission or sensing the ring gear in the differential.
The transducers in your generation Jaguar are not known for reliablity, and a common failure symptom is exactly what you describe. You'll need to be able to get under the car to remove and inspect the connector for cleanliness and corrosion. If it looks ok then you are to procede with replacing the transducer.
As for your door locks. These old cars are known for grease thickening up with dirt over the years and it can get so bad that opening the doors can result in broken handles! Remove door panels and to clean and re-lubricate the mechanisms inside.
Regards, Blake If a picture of what you are looking for is desired, then click on this following link -
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