Mercury Repair Questions? Ask a Mechanic for Answers ASAP
Hello. I would have to say the most likely reason for this is a plugged heater core. With the engine at operating temperature, feel the hoses to the heater core ( roughly 1" diameter hoses about 4 inches apart from each other going into the firewall). They should both be hot. If one is hot and the other is warm, or cool then your heater core is plugged and will need to be back flushed. This is accomplished by disconnecting the two hoses and flushing with a garden hose through the side that was not hot. make sure to run enough water through it to get it cleaned out well. If both hoses are hot then you will likely need a blend door actuator. If you have further questions please feel free to ask.
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