Heat problems.
 

'97 2500 454 Suburban. Heater works fine most of the time, as soon as it gets cold it just blows cold air the first time. The next time it may work fine.WTF

Re: Heat problems.
 

2 things come to mind
1,Happened to me on my 02 chevy. It was a fail open thermostat, and intermittently at first, then total. Thermostat stays open and engine never really heats up.

2. The main door controller for the heater is not closing to keep out the cold air from the heater core.

Both have happened to me.

If your engine temp gauge is getting up to its normal heat or hot range, then I would check the heater door controller (I believe its down near floor on passenger side beneath glove box area). If you engine temp is staying cooler than normal, probably thermostat.

Re: Heat problems.
 

Have you flushed it out lately,what a-freeze you running dexcool or has it been changed to green ?