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Q: Blower resistor stays on - 1998 Volvo S90

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We installed a used blower resistor and the fan blows all the time while the key is turned to on. The used one before this did the same thing. The car has a MCC climate control system. The fan switch didn’t turn it off. Could I test the resistor to see if it’s good with my digital multimeter? How do I rule out that it might be my climate control unit that is malfunctioning? The compressor doesn’t seem to be working either. Could the insufficient charge and low pressure switch be preventing the compressor clutch from working? Is my air conditioning compressor no good? We need to get this fixed before it gets really hot out.

A: Hello. It sounds like you may have a series...

Hello. It sounds like you may have a series of issues going on with the car. The blower motor staying on all of the time tells me that there amy be a relay that is sticking. It can be the control unit also. If the compressor is not turning on also then that may be from low refrigerant or it can be from the control unit also. It may also be a bad compressor. It sounds like the entire circuit needs to be tested with a voltage meter to find where the issue lies. Otherwise it would simply be a guess. If you want to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the AC system to ensure the correct repair is made.

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