Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSJAGUAR1991XJ-6 L6-4.0LREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGCONTROL MODULE HVACDESCRIPTION AND OPERATION
1991 Jaguar XJ-6 L6-4.0L
Control Module HVAC: Description and Operation
1991 Jaguar XJ-6 L6-4.0LSECTION Description and Operation
General Description
At the heart of the air conditioning control module is a digital micro-processor which receives data signals from driver controlled switches. By comparing this data with the signals received from the various temperature sensors and the feedback devices, it calculates the output voltages needed to operate the blower motors at the required speed and the flap servo motors to the required positions. It also controls the compressor and the vacuum solenoids to acheive the temperature requirements selected for the vehicle.
Although the control module cannot be repaired in service, a complete set of test pins are accessible for testing the system. Great Care must be exercised when connecting the test equipment for the control module will be irreparably damaged should any of the test pins be momentary shorted together.
At the heart of the air conditioning control module is a digital micro-processor which receives data signals from driver controlled switches. By comparing this data with the signals received from the various temperature sensors and the feedback devices, it calculates the output voltages needed to operate the blower motors at the required speed and the flap servo motors to the required positions. It also controls the compressor and the vacuum solenoids to acheive the temperature requirements selected for the vehicle.
Although the control module cannot be repaired in service, a complete set of test pins are accessible for testing the system. Great Care must be exercised when connecting the test equipment for the control module will be irreparably damaged should any of the test pins be momentary shorted together.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.