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Mercedes-Benz 300-Series
Timing Belts and Chains
Ford Expedition XLT
Heating Ventilating and Air Conditioning

How can I tell if the heating-cooling controller is bad on a 1990 300E?


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Wiki User
June 06, 2009 10:20PM

Without borrowing a known-to-be-functional unit, you would have to make sure your air conditioner is fully charged and that your Mono valve is working properly.