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Old 03-31-2000, 12:56 AM
jgl1 jgl1 is offline
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Join Date: Mar 2000
Posts: 517
Unrequested heat on a vehicle equipped with Automatic Climate Control is frequently caused by a defective heater monovalve. Your vehicle's ACC system uses engine coolant as the source of heat for adjusting the vehicle's interior temperature; coolant movement into the ACC's heat exchanger is controlled by the heater monovalve. This valve utilizes a rubber diaphragm attached to an metal plunger to gate coolant entry. Over time, the diaphragm fatigues and ruptures, allowing uncontrolled hot water entry into the heat exchanger. This diaphragm can easily be inspected and replaced: on a cold engine, locate the heater monovalve (on your vehicle - mounted on firewall, approx. inline with exhaust manifold); two engine coolant hoses and a power supply cable are attached to the valve. Detach the power cable and remove the four screws holding the valve's electromagnet plunger assembly in place. Remove the plunger and inspect the rubber diaphragm surrounding the plunger. Any loss of diaphragm integrity warrants diaphragm renewal. A repair kit is available from either Bosch or M-B and is substantially cheaper than a new monovalve. Installation is the opposite of renewal; correct for any coolant loss.
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