2004 Tahoe Heater Problem

check grill and radiator fins are not plugged and fan is not damaged and is working.
sounds like a thermostat or water pump issue.

That is pretty much normal, the heater blower fan acts like the radiator does and helps cool the water passing through it by extracting the heat from it. then once the car inside temp warms up it goes back to normal. Nothing to worry about.

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These details will help.
Thanks.

Sounds Like A Problem With your thermostat. Good Luck

Hi, the likely problem is a bubble forming in the system, possibly due to a head gasket failure.

Try stopping on a steep incline--does the heater stay warm? If yes, what you have is an air bubble that hangs at the heater hose until pressure from the water pump blows thru it as the engine speeds up. Park on an incline, open the radiator cap, run the engine until the thermostat is open, turn the heater on, crack open any/all bleed ports to release any trapped air, and fill the radiator to the neck. Wait until the level stops dropping and make sure bubbles don't continue to come up. If they do, you may have a blown head gasket that will keep forming these bubbles until you change the gasket.

Here's the thing. The ECU will shut down AC if the engine temperature is too hot. If the coolant temperature sensor is malfunctioning (lying to the ECU) telling it that the temperature is hotter than it actually is, the computer will turn the AC OFF.

you have air trapped in the cooling system. A good indication is that one or both of your heater hoses going into the heater core are cold when they should be hot.
Park facing uphill, raise front of vehicle so radiator cap is higher than top of engine. (You want bubble to get to radiator and out the cap.)
Leave cap on but loose, so bubble can purge.
Turn heater on.
Fill radiator and reservoir with 50/50 mix of antifreeze.
Start engine and run at about 1500 roms until the engine warms up and thermostat opens.
You will know themostat opens when top radiator hose is hot indicating coolant is flowing.
Shut off engine.
Fill radiator and reservoir. Install cap.

please Rate as fixya if this works. good luck

check your coolant level on the radiator

Sounds like SOUNDS like thermostat and a pressurised coolant flush would be a good place to start that thermostat might be opening and closing due to the above perfect place to start.John

If you smell coolant , there is a leak. I'm leaning towards a leak in the heater core if no fluid is visable and you smell it.
Pull the blower motor off and look inside to see if it is wet.
Have you had any issues with the radiator in the recent past? Maybe tried to correct it with stop-leak and didn't open the heater to full on hot? (maybe clogged the heater core up?)