Weak Airflow From Hvac

Discussion in 'Classic Mustang Specific Tech' started by Bullitt, Jun 11, 2013.


  1. Bullitt

    Bullitt Packin' Heat Founding Member

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    Been a long time since I've posted here, but finally getting my '67 A/C in working order (hasn't been functional really since I've had it). My car is a factory A/C car so it has the 3 speed switch. The ductwork is all in good shape and I haven't been able to identify any leaks. The vacuum lines are all new and motors appear to be working fine as air gets routed to the appropriate places based on the switch position.

    My issue is that the airflow out of the vents is really weak. The motor seems to have 3 speeds, but the airflow even on high is just not that much. I'm not expecting airflow like a modern car, but I would at least expect to feel the air from the driver's seat...

    The wiring is all brand new, so I don't think the motor is getting undercurrent or voltage unless the motor resistor is bad. Question is - if the resistor is bad, would the motor not work at all or would I get reduced speed like I'm experiencing?

    If the airflow is just the way it is, is there any blower motor upgrade out there that fits in the factory box? I'd like to avoid the expense of a complete redo on the system if possible.

    Any input would be appreciated!
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  2. Rusty67

    Rusty67 Well-Known Member

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    Hmm, I would check the air flow at the source just to start. Pulling that box out is a total pain. Maybe disconnect the main duct to it and stick your hand up there to feel the pressure ? I'm sure there are places that can rebuild the electric fan motor and upgrade the CFM output either with faster motors or a more efficient fin design on the fan.
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  3. iskwezm

    iskwezm Advanced Member

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    the resistor will reduce the voltage to the motor lowering the speed. Measure the voltage at the motor.
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  4. horse sence

    horse sence Please don't call me Mom SN Certified Technician

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    one of the vacume diaphrams that opens and closes the inside door has an adjustable rod check and see if the door is opening all the way. also see if it is leaking between the boxes they have foam rubber between them.
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