Heat come out of vent at hight speed at a idie it go cool have alot of heat out the back heater doul system why cool air on heat

SOURCE: leaking coolant from rear heater core in my astro van

you can hook the two line together that will fix your problem with no problems

SOURCE: Heating system only blows out hot air through the vents

I would look at the air blend doors first, it sound like they are not working or your control in the dash is not working send a signal to them. they work by changing the air from hot to cold or in between.

Avalanche, Sierra And Silverado

1. Remove the floor air outlet duct extension (1) from the floor duct (2). Remove the floor air outlet duct extension (1) from the floor duct (2)
2. Disconnect the electrical connection at the blend door actuator (10). Blend door actuator and related components
3. Remove the blend door actuator mounting screws from the HVAC module.
4. Remove the blend door actuator as an assembly with the actuator cam. Remove the blend door actuator mounting screws from the HVAC module

1. Install the blend door actuator as an assembly with the actuator cam.
   1. Line up the heater/defroster valve lever with the blend door actuator cam slot.
   2. Line up the A/C valve lever with the blend door actuator cam
2. Install the blend door actuator mounting screw to the HVAC module.
   1. Tighten the blend door actuator mounting screw to 14 inch lbs. (1.6 Nm).
3. Connect the electrical connection at the blend door actuator (10). Blend door actuator and related components
4. Install the floor air outlet duct extension (1) to the floor air duct (2).

1. Disconnect the electrical connector to the mode actuator that is located on the left side of the air distribution case.
2. Remove the screws.
3. Remove the adjuster links from the control lever.
4. Remove the mode actuator.
5. Adjust the mode actuator by completing the following steps:
   1. Connect the electrical connector to the actuator.
   2. Turn the ignition switch to the RUN position. Allow the self-positioning of the actuator.
   3. Turn the ignition switch to the OFF position.
   4. Remove the actuator from the electrical connection. Blend door actuator-C/K Series

1. Install the mode actuator.
2. Install the screws.
3. Install the adjuster links to the control lever.
4. Connect the electrical connector.
5. Test the circuit operation

SOURCE: WILL NOT SWITCH AIR FLOW STUCK IN DEFORST VENT

when your car is in defrost it has an ac cycling it removes the moisture then sends the air over the heater core depending on how warm you set it you can feel warm or cold but the ac is always cycling...ridding the moisture...you need a good ac tech it will be okay...its just expensive going into the heater core if needed...!

SOURCE: 96 suburban air conditioning blows out cool in front hot air back

Am investigating same problem. Download the free technical manual and you can find a diagram for the air mix door. If this doesn't shut you will be getting lots of heat through despite the cooling of the Aircon. I don't know how to get at it or fix it but it describes how to run diagnostics - you don't need specialist tools for this. Also a blocked pollen filter probably won't help.

Dean Hornberger

• 11 Answers
• Posted on Aug 29, 2012

SOURCE: Temperature gauge fluctuates and the heater blows cold air

Definitely check your fluid level in your radiator. Top it off all the way. I've seen that happen multiple times on cars that were low on anti-freeze. If that doesn't work try replacing your thermostat. It's cheap and the easiest place to start if topping off the fluid doesn't get you fixed up.