No heat at Idle.

Thankfully, didn't want to find out the hard way on Eisenhower pass in the dead of winter.

 

My money is on partially clogged heater core, especially if he has neglected cabin filter change/ cleaning intervals. It's all relative, and even if he has replaced/ cleaned it often, if he lives in an area with heavy debris out whether from trees or what have you, chances are it has gotten a partial build up of junk on it, especially at that mileage.

 

Oh shoot... thats NOT good. I'm sorry to hear about that OP. I don't know how I missed that post. Best of luck to you and I'm sorry to hear about your troubles.

 

How would a neglected cabin air filter clog a heater core?

 

I would go with a bit of a plugged up core remove both hoses and back flush the heater core.

 

lets face it people just do not read all posts before responding lol