hi, I have a 1984 too. Great year for the Series 3 XJ-6.

the orange light is the Bulb Failure Module Warning Light. It goes through a "check" of all Bulbs on the outside of the car after you turn the Lights Switch to ON, with Ignition Switch to ON. Then It lets you knowif there is a burnt bulb somewhere on the outside of the car by staying ON. If it comes on and stays ON when you step on the Brake Pedal, there is a Brake bulb that needs replacing.

If the emergency brake handle is ON, sometimes thelight will stay ON a little longer, so if you release the Emergency Brake Handle, it will go off.

The Speedometer has a transmission mounted speed sensor/transducer. It is an electronic Speedometer, (No Mechanical Cable).Check all wires leading to the transmission on the Left side. If everything looks good, and it still doesn't work, it is the Transducer gone bad.

I would try to get a used one first, replace it and see. Get whatever mileage it gives you, then after you learn the tricks, get a new one. Then you can compare prices, lots of parts suppliers all over the USselling Series 3 XJ-6 parts.

Get a Service and Parts Manual, around $25.00 in CD. Very handy to have.
The Series 3 XJ-6 (1980½ to 1987) is a simple car to service overall. the 4.2 engine is mostly bullet-proof. The BW66 transmission lasts a long time and it can be rebuilt. (it comes from the 1960's Studebakers). Lots of GM and DELCO parts in our cars: A/C Compressor, Air Pump, Power Steering Pump, Fan Clutch, Ignition Module.You can also getservice parts at Auto/Zone, CarQuest, O'Reilly's, NAPA, you name it.

Any Questions??

regards,
Jose

 

here is one place you can order a Service and Parts Manual for your model/year Jaguar:

http://www.lbcarco.com/cgi-bin/gen5?...ls+on+CD&o=

 

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here's a fresh link to Jaguar Service Manuals on CD:

http://www.lbcarco.com/cgi-bin/gen5?...;a=&t=_top