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Old 05-16-2013, 09:20 PM   #1
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Default Blend door

My heater/ac fan runs continuously. Does the blend module control the fan speed. It has the GM OE # 52402602 which I can't find anywhere. Any help is greatly appreciated. Ron
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Old 05-17-2013, 07:20 AM   #2
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No, it only controls the blend door. What kind of climate system do you have? Auto or manual?
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Old 05-17-2013, 08:56 AM   #3
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No, it only controls the blend door. What kind of climate system do you have? Auto or manual?
It'* a manual--sliders for temp and fan speed. I already replaced this unit and things were fine for a while but then the fan went to hi speed and wouldn't shut off. I pulled the fan motor and applied 12v to it and it worked fine. Can't find any indication of a blower resistor assembly anywhere. I theorized if it was shorted that would make fan run continuously.
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Old 05-17-2013, 09:47 AM   #4
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Unless the relay got stuck in the "on" position. When the blower switch is on low and medium, it uses a resistor to control fan speed. But when in high mode, it bypasses the resistor and uses a relay to deliver full 12V power to the blower. Or you have a broken blower switch.
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Old 05-21-2013, 08:56 AM   #5
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Unless the relay got stuck in the "on" position. When the blower switch is on low and medium, it uses a resistor to control fan speed. But when in high mode, it bypasses the resistor and uses a relay to deliver full 12V power to the blower. Or you have a broken blower switch.
Although I said manual I think it must be auto. The fan speed is not 1-2-3 speed but is infinitely variable by the unit in the center of the dash. Same for temperature. The Chiltomamual shows a blower motor resistor going to the Heater/A/c control assembly. But I can't locate it. Is it a part of the Heater/A/C Control Assbly? I'm stuck. Thank you.
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Old 05-21-2013, 12:15 PM   #6
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I'm not sure myself, but I did look up your 2004 Buick Lesabre on RockAuto Parts Catalog and it shows this as being your blower motor controller....



Not sure where its located in the vehicle, could be under the dash. But the AC Delco'* run about $88.
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Old 05-26-2013, 09:01 PM   #7
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Unless the relay got stuck in the "on" position. When the blower switch is on low and medium, it uses a resistor to control fan speed. But when in high mode, it bypasses the resistor and uses a relay to deliver full 12V power to the blower. Or you have a broken blower switch.
. Yes I agree. I checked all fuses and relays already. They're all ok which made me think the resistor had shorted ( perhaps a diode in the package).
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