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Topic: Heater blows cold

in Forum: C4 Cooling and Heating Systems

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Heater blows cold (1/3)
 1/14/22 4:47am
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Joined: 9/30/2021
Posts: 2

     My 85 blows cold air, no matter what the slider position is in.  The unit is placed in heat mode and the car was warmed up to 195. I thought that maybe vent was wrong and went through the defroster, vents and floor with no heat what so ever. The fan worked great. Any insight would be great.


     The tachometer worked when I test drove the car. After I had it in the garage, (starting and shutting the engine off) the tach went from 1500 RPM to nothing.  




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Re: Heater blows cold (2/3)
 1/14/22 9:33am
Black Shark
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Black 1979 L-82 Black 1996 LT1 Black 1999 Coupe

Joined: 3/20/2009
Posts: 589

If hot water is flowing thru heater core; inlet and outlet side will be hot.

The above determines if valve is working correctly and if core is NOT restricted.


Other diagnostics follow after this is determined.

Re: Heater blows cold (3/3)
 1/14/22 10:39am
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, - Canada

1993 C4 - Red, 6spd

Joined: 9/25/2020
Posts: 1

If you aren't smelling anti-freeze inside or the windshield isn't fogging up, you probably have a stuck blender door which is quite common as well. 



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