72 Heater Switch Problem
Thread Starter
Cruising
Joined: Sep 2012
Posts: 10
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72 Heater Switch Problem
Just got my windshield wiper working and now the blower motor is acting up. It's the weirdest thing. With the fan speed control in the "off" position, I can hear the blower motor. In the high position, it turns off. It also turns off when the "mode" **** is in the "off" position. Another thing, when I hear the blower running, no air comes out, no matter what mode I'm in. I removed the air conditioner compressor awhile back. I'm not sure if that wiring would affect the operation of the blower. Help Please!
Ed
Ed
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Welcome!
There is a 30 amp in line fuse for HIGH speed, on the engine side, look under the left fender it may be bad.
You have Astro or flo-thru ventilation so the blower motor will still be running even with the switch in OFF. On some models turning the thumb wheel to Off will turn off the blower.
Take a look at the duct work, something could be missing or loose.
You have Astro or flo-thru ventilation so the blower motor will still be running even with the switch in OFF. On some models turning the thumb wheel to Off will turn off the blower.
Take a look at the duct work, something could be missing or loose.
Advanced
Joined: Jul 2007
Posts: 72
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If it is not the fuse then it is likely that the high speed relay for the fan is bad. I have had both issues but I understand that a bad relay is more common. The relay is mounted near the fan in the engine compartment. Replacement relays are readily available.
Team Owner
Joined: Jun 2000
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From: Southbound
Cruise-In II Veteran
If you can hear the blower motor, it's running.
Fan speed is determined by the resistor in the AC case near the motor.
Air flow is determined by vacuum from the AC console switch which opens and closes the selector air door as needed based on what mode you select.
Sounds like your selector door is not opening/closing.
Do you have air out of the defroster grille?
The AIM has a diagnostics page for testing the stock AC system. Read through it a time or two and you will pick up on what is supposed to happen at each mode selection on the console.
Fan speed is determined by the resistor in the AC case near the motor.
Air flow is determined by vacuum from the AC console switch which opens and closes the selector air door as needed based on what mode you select.
Sounds like your selector door is not opening/closing.
Do you have air out of the defroster grille?
The AIM has a diagnostics page for testing the stock AC system. Read through it a time or two and you will pick up on what is supposed to happen at each mode selection on the console.
