Heater works fine.... no defrost till moving.

[G.averill]

Hey guys. So this is my first winter with my 2005 GMC Sierra 1500 5.3l.

 

I'm sure I've missed something in the search, but couldn't find anything talking about my "issue".

 

So. During the mornings, I go out to start the rig. I've let it set for who knows how long but after the gauge reads it's at full operating temp, it still doesn't blow hot or even warm air to defrost. But if I let it run for about 5-8 mins and gently get the Rpms going, after a couple cycles of up to about 1500rpms and back (again, gently) it'll start blowing warm. Or even if I don't do that I'll barely get halfway down the block and itll start blowing hot as the devils breath.

 

 

Now, the first thing I thought was tstat, changed that and did a flush.... still no warm on idle. Just much warmer when I get going.

 

Again, sorry if this is a old topic and I missed other threads.

 

If you might know what's going on or have ideas or know it's just how the engine runs... any insight would help.

 

Thanks in advance.

[NBSFan]

Kinda sounds like a control panel or actuator issue . If nobody else chimes in here try looking the issue up on you tube and that might help you pinpoint the issue.

[G.averill]

@NBSfan. I've tried for about a month now, no luck. But I will try check out these on there. Thank you.

[txab]

Make sure the cooling system is completely full.Low level can effect heat performance. Also did you flush the heater core specifically?

[G.averill]

I didn't specifically do the heater core. Just a basic flush.

[txab]

Then it flush it now