My truck just did the exact same thing -- and it was a Sensor -- cost me $40.00 to get repaired at a local auto repair shop.
"Engine hot, a/c turned off" light is blinking. Temp gauge stayed on 160. Doesn't seem like engine is overheated. Fan sounds louder. (2009 GMC Sierra)
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.
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
SOURCE: ac clutch will not engage 1998 gmc sierra
sounds like low or no refridgerent in the system. start there. You can the cycle switch (low pressure switch on the side of the reciever dryer. the alumunium can on the left side of the engine in the back. You can also jump the two pins with a jumper wire and see if the compressure turns on then. Do not let it run for more than a min. you could burn up your compressor.
Good luck
SOURCE: 2004 gmc sierra 5.3. AC not working AC Compressor fuse blowing
UNPLUG THE A/C CONNETOR ON THE A/C COMMPRESOR. REPLACE THE FUSE AND TURN ON THE SWITCH. FUSE OK . REPLACE THE COMMPRESSOR AND THE RECIVER DRIER.
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
Testimonial: "Very good information. THANKS!"
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