Question about 2006 GMC Envoy

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Heat is cool to lukewarm when turning dial through temperature range (60-90) until reaching 89. Then it very warm, as expected. But all the way thorugh 88, the air coming from all the vents is only likewarm at best.

Posted by Fred Becka on


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Cody Campbell

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Could be a variety of problems. Could be the switch?

Posted on Sep 14, 2013


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  • 1 Answer

SOURCE: 2005 GMC Yukon air conditioning

this just happen to me 2005 denali; dead battery in the morning, replaced it...and I have cold on drivers & screaming hot on there a fix posted....& I just dont see it?? what gives?

Posted on Sep 05, 2008


Ronnie Houston

  • 2920 Answers

SOURCE: 2004 GMC Sierra Heater does not heat on low RPM

check your coolant level on the radiator

Posted on Feb 03, 2009


  • 91 Answers

SOURCE: AC is cold, then hot..

you need the tempature blend door motor. My 01 silverado had this issue about 1 1/2 years before i was tired of messing with it they are not hard to replace. The cover (if it is still on) for passenger side floor ducts needs to be removed and the motor is near the right side of "hump" (trans tunnel) mounted horisontial with the armature pointing upwards.

Posted on Apr 27, 2009


  • 1 Answer

SOURCE: 2006 GMC Denali front heat works only cool air

I am having similiar problems with my 06 Denali. Mine does the same thing but also does not blow hot air when in idle.

Posted on Nov 18, 2010


Bobby Blevins

  • 229 Answers

SOURCE: i have air coming out of my defrost and heat, but not hot air, but have hot air going to the rear heat. 2003 GMC Savana

You have either a blend door problem,or the blend door actuator. Both are located underneath the dash.

Posted on Sep 24, 2012

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That is normal cooling fan operation. the fans are computer controlled and not turned on until the engine reaches the pre programmed temperature, that is about 185-195F

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I replaced the thermostat in my 1998 subaru forester. How do I know if it is openning when it needs to? How can I test the pressure in the radiator? What should the pressure be in the radiator?Thank...

To test your new thermostat, do the following
1. Make sure your heater is off.
2. Start your engine and allow it to run for 6 to 8 minutes so it can reach the normal operating temperature.
3. Turn your heat tmperature select all the way up, and then turn the fan on high. You should hear the thermostat click when it opens up to circulate the coolant through the system. You may also notice your temperature gauge reading lowering.

The only pressure you may have in the radiator/cooling system is very minimal and caused by the coolant heating up.Whenever pressure starts building , it is purposefully relieved through your coolant reserviors overflow hose. Thats why you should never fill your coolant reservior all the way up. It needs to have 3 or 4 inches to allaw for expansion.

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The cable that pulls the cool/heat switch on the a/c gets weak and it doesnt allow the dial to switch over to heat. You can see that cable and the way its supposed to work on the right side of the gas pedal over it. I usually just use my foot to push that switch over to heat and reach with and pull on it with my right hand to cool.

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'95 Mazda 626 LX 6cyc - Heat is spuradic...I notice the temp gage will spike and then the heat will get warm and it will return to the normal range?

You have air in your cooling system. Fill your cooling system when the car is cold. First check the radiator if it has a cap, fill that first, replacethe cap tightly, then fill the overflow tank to the indicated level. Start it and turn the heater to the full hot position. Let it run untill it reaches opperating temperature. Quickly squeezing the upper radiator hose 3 or 4 times every now and then to "burp" the system. look for leaks. If this does not solve the problem you may possibly have a headgasket leak.

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No heat air is blowing cold

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced.
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is worm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest to flush the heater core.

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The problem is with the heater.

3 words come to Mind. Heater Blend Door

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Nissan Altima no cool air blowing or hot air blowing

It appears we have an Air lock scenario and you will need to perform a system Bleed.
Park the vehicle on level ground, when cold remove coolant filler cap, start engine and leave to idle, turn heater on full and blower to max. When engine reaches operating temperature watch and listen near coolant filler, keep clear as gurgling and hopefully a boil over should occur. Top up with very warm coolant and wait as it may do it again.
Check for heat inside vehicle if warm replace coolant cap but keep an eye on temperature gauge as the ~Air lock may have moved on from heater matrix/core so proceedure needs to be carried out again from COLD.

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Paul 'W' U.K

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