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Low heat and air circulation problems

Jaryd

Extremely Deplorable
Messages
1,959
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3,319
Location
Hodges, SC
For the past year or so when I go to cut the air condition or heat on it takes a minute for the air to come out of whatever vents the knob is on. The fan speed has always worked as it should but sometimes when I cut the fan on I can here the fan in the dash running but the airs not coming out of the vents anywhere. I have to cycle the vent selection knob or the fan speed knob on and off a few times and then it’ll work.

Question is what should I look at? The switches on the dash or the stuff on the fan (pigtails, diodes.....I don’t know what all makes it work)? I looked through some of the threads that has popped up recently about this but still have no idea where to start.

Next thing is I have had LOW heat ever since my last heater core went out about 2 years ago. When the heater core started leaking I had normal heat. Once I changed it out I never could get real heat again. I flushed the BrassWorks heater core to make sure it wasn’t plugged. It was fine. I changed to a 195* TSAT and flushed the engine. Before I put the BrassWorks core in again I watched what blend doors I could see (looking up into the dash from where the core goes) move when I turned the knob on the dash.

Next question is where do I go from here?

I think I have two problems going on. The low heat problem and the blend doors not working as they should.
 
Focus on the blend doors. Door sealing, and full movement.

I personally hate that gm always defaults to fresh air. Cycles the doors and wears things out to fast on already lower quality parts compared to Ford or Dodge full size trucks.
 
IIRC there's 3 blend door motors. The one before the fan controls the fresh air/ recirculation mode. One controls the temperature by blending fresh or recirculated air through or around the heater core. The 3rd controls where the air comes out of the dash
 
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