Question about 1991 GMC Sierra

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I need help, the heater in my 1991 GMC Sierra stopped working and blows only cold air, the button to change the air temp shows hot but no hot air

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Posted on Jan 02, 2017

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  • 958 Answers

SOURCE: 2005 GMC air conditioning

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drcool299

Posted on Sep 23, 2008

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  • 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

  • 1 Answer

SOURCE: 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

Posted on Jan 04, 2009

emissionwiz
  • 85178 Answers

SOURCE: my air blows hot even tho my climate control is on cold

U have a stuck air temp control blend door, either the actuator motor is defective or the door is warped and has jammed, one thing is that u must remove the dash to rcheck replace these parts.

Posted on Mar 10, 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

Heater blows cold


ok there is a few things might be happening...first did you make sure when you put the intake gaskets in there was No ports plugged or covered...second is...are both heater hoses Cold or is one hot and other cold...if so you have a air lock in the heater core...if this is the problem you need to lossen off the cold one till antifrezze comes out.

Mar 06, 2010 | 1989 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

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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

1 Answer

2005 gmc siearra blows cold air


sound like blend doors are not working there is a motor under dash or vacuum line under dash ant working they should be color coded red yellow black i think need more let me know

Aug 10, 2009 | 2004 GMC Sierra

1 Answer

My air blows hot even tho my climate control is on cold


U have a stuck air temp control blend door, either the actuator motor is defective or the door is warped and has jammed, one thing is that u must remove the dash to rcheck replace these parts.

Mar 10, 2009 | GMC Sierra 1500 Cars & Trucks

1 Answer

2004 GMC Sierra Heater does not heat on low RPM


check your coolant level on the radiator

Feb 03, 2009 | 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

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