Heater blower

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1970Dart340Swinger

1970Dart340Swinger

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Blower functions on all speeds when either A/C or Max A/C is selected. No blower on heat or defrost. I replaced the A/C and heater blower switch/vacuum module but no change. Good 12v to green and black wires on back of module.
Does engine need to be running to create vacuum? Not runable right now.
any thoughts?
 
I realize that the engine must be running to create vacuum, but are you saying that vacuum is needed at the switch for the heat and defrost to function?
 
Not totally familiar, but if it is a vacuum operated board, yes. You may be able to look up there and see the vacuum hoses.
 
Connected the vacuum cleaner and the flapper valves that divert air to the defrost, etc, moved, but the blower does not run in either heat or defrost. Seems strange to me that the blower would run with the A/C button pressed but not in heat or defrost. I'm thinkin that the new switch I installed that cost me $120 is defective. The wiring diagram is straight forward-- 12v to the switch with no different external contacts for A/C or heat, and no provisions for an engine temperature input that might delay the blower in heat and defrost.
 
DA65RT said:
Connected the vacuum cleaner and the flapper valves that divert air to the defrost, etc, moved, but the blower does not run in either heat or defrost. Seems strange to me that the blower would run with the A/C button pressed but not in heat or defrost. I'm thinkin that the new switch I installed that cost me $120 is defective. The wiring diagram is straight forward-- 12v to the switch with no different external contacts for A/C or heat, and no provisions for an engine temperature input that might delay the blower in heat and defrost.
Click to expand...
I'm having the very same problem-- Did you find a fix?
 
The blower works differently between heat and ac. The blower only runs on full power on ac high speed. On heat, one of the blower resistors is in the circuit on all speeds. Don’t know it this helps you.
 
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this is the blower motor resistor it goes in the top of the heater housing you will need a super short #2 philips and a lot of luck to remove it with the heater housing in the vehicle!
 
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