Heater core is hot but no heat.

[Kagenh]

Hi forgive me if this is in the wrong spot but my heater isnt working in a 1996 gmc sierra. The upper and lower hoses are hot but when the air blows its slightly warmer then cold. Also the defrost is always on but also the indented vent still work the defrost just works at the same time.

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[superdave]

Probably the heater blend door actuator located behind and lower than the glove box

 

[Kagenh]

Probably the heater blend door actuator located behind and lower than the glove box

For both problems? Or just the heat?

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[c1500deathtrap]

There are two little flappy doors in there. one for temp and one for direction i.e. floor, dash, or defrost. Some systems have more doors some less. i honestly don't remember how many we get.

 

[superdave]

For both problems? Or just the heat?

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That one is for the heat. There is another one under the dash for the vents.

 

[joep88cheyenne]

Could be a plugged heater core. Mine is plugged, I know this for a fact as it hasn't been hot since I got it last year. I drained and flushed my system and both hoses hot but the core is cold to touch. I have a new core to put in and a thermostat also just haven't had much time to work on that. I will be doing sooner then later as weather is going in and out of comfortable in my neck of Texas.

Added: both of my hoses are hot because one comes off the intake (stupid setup) and the other is getting heat from the radiator on the return side of the core.

 

[east302]

For both problems? Or just the heat?

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The one by the gas pedal controls the floor-defrost-vent setting.

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See if the linkages and springs are all intact. Watch the notched dial--see if it rotates as the control panel setting is changed from floor to dash to defrost.

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The one that controls the temperature looks the same and is located, roughly, behind the ashtray. Pull the glove box to get a better look and see if the dial rotates as the temperature dial is changed on the panel.




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[superdave]

The little plastic pieces on the links can break and the linkage just falls apart. The linkages are easily replaced