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I have the identical problem on a 1991 Jimmy. I have replaced the blower motor and flushed the heater coil. I know the vents are working properly because they work when the temperature is selected to cold. I am wondering if there is something under the hood that redirects the aif flow either through the cooling coil or the heater coil based on the position of the temperature control. If so possibly the heater coil (air side) is clogged. I noticed that the heater coil is below the AC coil so it is possible that debris is down in it. I may try to pull it and clean it. Have you tried that?

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โˆ™ 2008-01-07 13:23:13
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Q: What is the cause of 1995 jimmy with no heat coming from main vent Defrost is fine as well as floor heat When turned to cold side air flow increases When turned back to heat air flow subside?
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