Jaguar Repair: 86 XJ6 Heater Fan & Temp gauge both stopped working, climate control system, dash vents

Question
QUESTION: It may be coincidence, or something electrically common, that both are cooling system related.  

In any case, the temp gauge has stopped registering, and, within the same day, the heater fan does not come on with the switch in any position, including defrost, which evidently is not thermostatically driven.  Warm air is still coming out of the windshield's vents and the dash vents, but not with any fan-driven velocity.  

With regard to the gauge, all other dash instruments are working normally.  Could you please suggest where I should start, with respect to both, or individually?

Thanks.

ANSWER: Hi Allen,
All gauges operate off of one power supply (fuse #4) Neither fan is powered by that fuse. The heating and AC system are powered by fuse #6 and #16.
Since you have neither fan on no speed then you probably can rule out the resistor that changes the speeds as full speed does not use the resistor.
The Climate control system is very complicated and the diagnosis of the system is several pages long and you need to purchase the AC/Heat manual to get the diagnosis procedures. It is far too much to cover in e-mail.
You may be able to do some diagnosis using the wiring diagram which I can put up on my web site for you to copy if you don't have it. let me know.
Howard

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

QUESTION: Thanks for the quick response.  Just to summarize, the gauge problem is probably in the sending unit side, since the other gauges are working.  And, regarding the fan, if the fuses (#6 and/or #16) are intact, the problem must either be the fan motor itself or a failure along the wire connections to the fan.

Is that a fair summary?

Answer
Yes, If it were mine I would first use a jumper to power up the fans to see if they are good. Then take your wiring diagram and ID the power wires on the multi relay on the left side of the console under the kick panel and you can do a lot of testing right at that relay with your diagram. Everything in the AC/Heat system is operated by a rotating drum which works micro switches and vacuum switches. If the drum stops operating then nothing happens. The drum is powered by a small electric motor.
Howard