I had the dealer replace the actuator a few months back since the rear didnt blow hot air. Now the AC doesnt blow cold air, could it be the same actuator problem? I dont want to check with you guys first before bring it back to them for diagnotis :). btw, it is a 2003 tahoe LT.

Thanks you,

Welcome to AF.
If auto AC controls.
First try a recalibration on it.
Key off.
Pull the radio fuse for a minute and then put it back in.
Turn key on and see if it cycles from hot to cold and works right.
If not you will need to check for body codes to find the problem.

thanks, recalibration did the trick. Now what was the root cause of that issue? Do I need to replace something? Also, one of my running light keep burnt out. Is it because of a bad relay? Can I replace the relay myself or do I have to bring it to a mechanic?

Thanks you in advance.

You are welcome. Glad all is well on ac now.
Recalibration is a normal procedure.
When parts are replaced or work done on them sometimes the need the recalibration to refresh there memory.
Also a weak battery or bad wiring or ground or even jump starting can mess up the recalibration .
The recalibration is just like rebooting a PC.!!!
On the light burn out is the bulb burning out or just not getting 12 volts to it or a bad ground?
Is he plug in and wiring to it good?
Is your battery and charging system up to par?

I suspect there is something wrong with the little white housing unit (where you plug the light bulb into), it worked for a few minutes after I twist it a bit. Is it easy to change it? can I get the new part from local part store and replace it myself.