Ok having a heater issue and I think I know what the cause is but want you alls thoughts.

Here's what happens. At idle cold air comes out, driving hot air. Temp gauge at idle hovers around that 210 mark, driving more around 180-190. So basically I get heat when driving but not at idle. Very odd.

My thoughts are sticking t-stat. What's yall thoughts?

 

I have had that issue before and it was low coolant.
Thats were I would start if I was you. good luck

 

Guess the thermostat could be the culprit.

I'm also thinking perhaps the heater control valve isnt getting enough vacuum at idle and closing the flow to core? So the fluid in the core gets cool quick with blower on and no flow?

With this cold snap perhaps the plastic vac line is cracked somewhere?

 

Does it work with the key in accessory?

 

Low coolant level, stuck heater valve, questionable water pump, or maybe it's time for a flush/fill.

 

Well I solved the riddle. Was low coolant and good thing I checked it, was a galon low. What happened somehow is the tube that goes from the radiator to the overflow bottle came off at the bottle end. So it has been slowly leaking coolant. Needles to say I reclamped it and added coolant and heat comes alive.

I guess I had enough in there that even be well below freezing it didn't do any harm. Check the oil and so on so no head gasket issues.. I hadn't even considered checking the coolant level.