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2007 gmc sierra heater only blowing cold air, both heater hoses are hot

A/c works fine switch to heater no heat just cold air

Posted by Anonymous on

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6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

  • 1 Answer

SOURCE: 200 gmc jimmy st heater

Had similar problem in my 2000 Jimmy. No hot air from heater. Had the shop (Midas) disconnect heater hoses at the fire wall and blow out the heater core with air hose. Got rust and junk blown out. Hooked up and flushed system with new anti freeze. Got lots of heat now.

Posted on Nov 09, 2008

  • 1 Answer

SOURCE: 2000 GMC Sierra 5.3 Litre, won't blow hot air

I experienced the same head ache. First attempt was to replace the thrmostat and after taking it apart I realized that there was nothing wrong with it. I then removed the plastic cover/panel located under the dash board on the passenger's side. (only a few 4-5 smalls screws) Removal will enable you to see the on/off switch/gate moving/rotating as you turn the knob to hot or cold positions, on the control panel. If that switch/gate seems to work ok, then the trouble is within the heater core. Many mechanincs suggested that I replace the heater core. A very expensive proposition.
I checked the heater core supply/intake hose and found it hot to the touch, while the return hose was nearly cold. It was definitely a heater core blockage. I removed both ends (supply and return) hose connections/clamps. They are located near the fire wall in the engine compartment. A special tool is very helpful to remove those clamps easily and to replace them as well. It can be done the old fashion way but this tool was a life saver and reduced work time to just minutes. (Tool is $70.00 bucks at auto parts store,so I borrowed mine from a mechanic/friend)
I then hooked up a garden hose to the return end of the heater core and reversed the flow of coolant/water through the heater core. My truck is a Sierra 2000 and I refuse to see how a heater core could get clogged up with clear coolant alone. To my surprise a flat piece of rubber about the size of a quarter blew out of it and the flow of water became unobstructed. I reconected the ends of the hoses to the heater core, replaced the lost antifreeze & everything returned back to normal. No money spent for something most mechanics suggested I replace control valves/switches ($280.00) replace heater core ($500.00) etc etc. I am glad I was curageous enough to tackle this myself and save a few pennies. Good luck, and I hope this will work for you.

Posted on Dec 02, 2008

  • 2920 Answers

SOURCE: 2002 GMC Yukon blows cold air from the front, rear works fine

check you antifreeze level and make sure its full

Posted on Jan 26, 2009

  • 169 Answers

SOURCE: The air conditioner is blowing hot air on the driver's side only.

poss ac vent elec valve under dash bad

Posted on Aug 29, 2009

  • 6 Answers

SOURCE: 2000 gmc sierra 1500 5.3 v8. a/c heater control problem

your heat/cool and vent selection options are controlled by engine vacuum through small clear tubes attached to the rear of your climate control interface. Other vehicles have small steel pull wires that operate the desired changes. You might try removing the trim and any fasteners affiliated with the interface/console. GENTLY pull outward and look to see if any of these tubes are pulled off or cut/damaged. Did anyone recently install a new stereo in the vehicle? If so, the vacuum tubing and or pull wires that change your outlets could have been damaged when the stereo unit was pushed into place. Hope this helps

Posted on Sep 09, 2009

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1 Answer

1989 GMC Sierra 1500 heater blows cold air. Changed thermostat. Both hoses are cold.


check antifreeze level add if low, and check intake heat control valve on ps side of intake if its locked shut it can be removed and a water pipe nipple put in place of it and the heater hose reconnected..if the water pump is good, it should give heat this valve should be on the intake with a heater hose connected to it..and its vacuum operated but will jam shut with age and cold weather..good luck..

Jan 19, 2013 | 1989 GMC Sierra

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I have a 2005 GMC Sierra regular cab. 4.3 v6 The heater has only been blowing cold air. Checked coolant and replaced the thermostat. No change. AC worked fine this summer. Heat worked fine last...


sounds like you have a bad temperature door actuator. This is a motor that connects to the door and uses inputs from the sensor in itself and the heater control module to open the door from hot to cold. I does take some knowledge on recalibrating this actuator and installing it. if it isn't install correctly it could damage the new part, so just take care

Sep 16, 2011 | 2005 GMC Sierra

1 Answer

I just changed thermostat, and replaced coolant, still my 1995 gmc suburban blows cold air.


Find the two heater hoses going through the firewall to the heater core both need to be hot at operating temp. If both are hot the problem will be inside with the heater control. I only one heater hose is hot the
problem will be the heater core. I am assuming you have bled all the air out of the cooling system.

Feb 25, 2010 | 1995 GMC Sierra

2 Answers

2005 GMC Sierra 1500 - heater blows, but only cold air


Check coolant level. Check for heat at the heater hose going from water pump to heater core at firewall. Check to see that cable is moving coolant control valve from the closed to open position. Low mileage so it shouldn't be plugged heater core.

Jan 07, 2010 | 2005 GMC Sierra

3 Answers

HEATING PROBLEMS


Need more information. The most important thing would be to watch the heater water valve move when someone turns the control from hot to cold, back and forth?
Heater valve controls tend to be operated by vacuum, and switched by a heater computer. Lots of possibilities. But first tell us what you see move when operated? Valve is usually in engine compartment, in the heater hose. Follow the hot one.

Jan 03, 2010 | 1999 GMC Sierra

4 Answers

The heater still won't work after I changed the thermostat on my


Get a female garden hose adapter from the local hardware store. Disconnect the heater hose from behind the fan pulley and attach the hose connection. Disconnect the other heater hose behind the alternator, aim it towards the ground and flush water through the heater core. This worked on my truck.

Feb 12, 2009 | 1999 GMC Sonoma

1 Answer

2000 gmc sierra 5.3l heater does not get hot


After replacing the thermostat I pulled the heater hoses off and blew air through the heater core at firewall. Can only blow in left side as directional valves will prevent opposite. Chunks of stuff came out with coolant. I then put a piece of hose on the left side and shot water through until it came out clear.
Put it all back together and heat works fine.

Dec 31, 2008 | 2000 GMC New Sierra 1500

1 Answer

93 gmc sierra heater not working


THERMOSTAT REPLACE IF NOT SEE IF HOSES ARE CLOGGED SHOT OF AIR COULD HELP OR DISSCONNECT BATTERY CABLE 10-15 MIN CONNECT BACK TRY HEATER

Dec 20, 2008 | 1993 GMC Sierra

3 Answers

2000 GMC Sierra 5.3 Litre, won't blow hot air


I experienced the same head ache. First attempt was to replace the thrmostat and after taking it apart I realized that there was nothing wrong with it. I then removed the plastic cover/panel located under the dash board on the passenger's side. (only a few 4-5 smalls screws) Removal will enable you to see the on/off switch/gate moving/rotating as you turn the knob to hot or cold positions, on the control panel. If that switch/gate seems to work ok, then the trouble is within the heater core. Many mechanincs suggested that I replace the heater core. A very expensive proposition.
I checked the heater core supply/intake hose and found it hot to the touch, while the return hose was nearly cold. It was definitely a heater core blockage. I removed both ends (supply and return) hose connections/clamps. They are located near the fire wall in the engine compartment. A special tool is very helpful to remove those clamps easily and to replace them as well. It can be done the old fashion way but this tool was a life saver and reduced work time to just minutes. (Tool is $70.00 bucks at auto parts store,so I borrowed mine from a mechanic/friend)
I then hooked up a garden hose to the return end of the heater core and reversed the flow of coolant/water through the heater core. My truck is a Sierra 2000 and I refuse to see how a heater core could get clogged up with clear coolant alone. To my surprise a flat piece of rubber about the size of a quarter blew out of it and the flow of water became unobstructed. I reconected the ends of the hoses to the heater core, replaced the lost antifreeze & everything returned back to normal. No money spent for something most mechanics suggested I replace control valves/switches ($280.00) replace heater core ($500.00) etc etc. I am glad I was curageous enough to tackle this myself and save a few pennies. Good luck, and I hope this will work for you.

Nov 11, 2008 | 2000 GMC Sierra

2 Answers

200 gmc jimmy st heater


Had similar problem in my 2000 Jimmy. No hot air from heater. Had the shop (Midas) disconnect heater hoses at the fire wall and blow out the heater core with air hose. Got rust and junk blown out. Hooked up and flushed system with new anti freeze. Got lots of heat now.

Oct 25, 2008 | 2000 GMC Jimmy

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