Defrost Problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72YellowBird · 10-29-2007, 06:23 PM

I have an 86 GMC pick up with factor A/C that blows very little defrost air out of the vents when the defrost switch is selected. It seems to work fine on any of the A/C positions with air blowing from the vents and the defrost vent is cut off. When defrost is selected the air still blows from the A/C vents and out of the defrost vent. It doesn't shoot all the air through the defrost vents. Seems to work properly on heat air is coming out of the heat vent. You can hear the vaccum hiss when seletor switch is moved.Can't seem tofigure it out.

10-29-2007, 06:23 PM	#1
72YellowBird Registered User Join Date: Mar 2006 Location: Airdrie,Alberta Canada Posts: 41	Defrost Problems I have an 86 GMC pick up with factor A/C that blows very little defrost air out of the vents when the defrost switch is selected. It seems to work fine on any of the A/C positions with air blowing from the vents and the defrost vent is cut off. When defrost is selected the air still blows from the A/C vents and out of the defrost vent. It doesn't shoot all the air through the defrost vents. Seems to work properly on heat air is coming out of the heat vent. You can hear the vaccum hiss when seletor switch is moved.Can't seem tofigure it out.



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