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 MANUALSJAGUAR1985VANDEN PLAS L6-4.2LREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGCONTROL MODULE HVACDESCRIPTION AND OPERATIONAMPLIFIER
1985 Jaguar Vanden Plas L6-4.2L
Amplifier
1985 Jaguar Vanden Plas L6-4.2LSECTION Amplifier
Amplifier
Function: Automatic temperature control is achieved by comparing the in-car temperature at the sensor with that set at the manual temperature selector. Any difference in these two settings causes an IMBALANCE voltage situation in the amplifier which in turn signals the servo control motor through a relay to rotate the camshaft to either the heating or cooling mode.
When the camshaft rotates, a feedback potentiometer also rotates and as the system starts to heat or cool the interior, the feedback potentiometer commences to return the camshaft back to the balance position. Any sudden change in ambient temperature is sensed by the ambient sensor and through the in-car sensor can modify the camshaft position calling for more heating or cooling before the in-car sensor could reflect the ambient change itself.
Main Blower Relay:
Function: Automatic temperature control is achieved by comparing the in-car temperature at the sensor with that set at the manual temperature selector. Any difference in these two settings causes an IMBALANCE voltage situation in the amplifier which in turn signals the servo control motor through a relay to rotate the camshaft to either the heating or cooling mode.
When the camshaft rotates, a feedback potentiometer also rotates and as the system starts to heat or cool the interior, the feedback potentiometer commences to return the camshaft back to the balance position. Any sudden change in ambient temperature is sensed by the ambient sensor and through the in-car sensor can modify the camshaft position calling for more heating or cooling before the in-car sensor could reflect the ambient change itself.
RENDER: 1.0x
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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.