I seemed to have solved the temp control issue on my 2004 Silverado.
The passenger side worked normal but the drivers side would only blow hot air.
This symptom started after trying to solve a different problem by disconnecting the battery. (it didn't fix my other problem and caused this one)

1. Turn off engine. Key in OFF position.
2. Remove all three HVAC fuses. Two under hood, one inside the cab.
3. Turn all ac/heat controls to OFF and temp controls to cold.
4. Replace all the HVAC fuses.
5. Start the engine, AND LET IT RUN FOR 5 MINUTES.
6. After 5 minutes I turned on the fan, and the temperature controls worked normally.

If any one has an Idea how to get the factory RADIO/CD player to eject the CD it has eaten, I would be grateful.

2004 Silverado. Love the truck but a few months ago the fan control started to work at only 4 or above. There was a clicking from what I assume is the actuator. Now when the truck idles with the heat in, it blows cold air. If I drive for a bit the heat starts. The engine does not over heat. Any ideas, folks?

heater problems
 

I have a 2012 impala and the heat went out a few weeks ago for a day then it came back on the following day...now the heater went out again and its not coming back on....it doesnt work at any speed so im not sure if its in the controls or the blower...

I have the same problem with the drivers side going from a/c to heat while the passenger side stays on a/c, it will switch back to a/c after some time or I shut off the truck for 1 min. And start it up and it is back to a/c. ( what do you thick is the problem)

Blower motor only working on high speed or reduced number of speeds is nearly always the blower motor resistor.

Basically, the 2 5.5mm screws attached to the blower motor in model years 1999 to 2005 that I can verify due to owning said model years.

Just to be thorough, I would ensure the blower motor and resistor wiring is plugged in firmly and 100%. My cirrent 1999 truck has got 0 parts issues, but the blower motor be on a helluva rave.

Random speeds, random times. In my case its all jankin' ass cheap as frig Cheby brand wiring. Nothing some epoxy and zip ties wont cure.

Ramble over:

Check the blower motor resistor. If you vehicle is newer than 1999 the blower motor relay could have died also. Blower relay tends to equal no blower motor at all but functioning mode and blend doors.