It's not the cabin air filter. It's not going to be the coolant / water ratio.It's a somewhat decent car, and just my winter beater/back-up car. The other 2 cars I have I don't drive in the winter time. I've wanted them to diagnose the lack of heat, and they suggested a new thermostat (despite the fact that I already had it replaced 3 years ago from another dealer/my previous employer). I'm pretty much at my wits-end about why I can't get fully hot heat. I've seen the 2 YouTube videos above, and unfortunately I'm not too much of a mechanic myself. I've changed the regular air filter but I was completely unaware my 2002 Sable GS would be equipped with a cabin air filter.
My next service appointment with my mechanic is this coming Thursday 1/30. I will have him investigate the blend door, cabin air filter, and coolant/water ratio. Anything else I can ask him to investigate?
The diagnosis is quite simple. If you're really incapable of doing it, then you need to find a mechanic who can, because obviously your current one is more interested in ripping you off.
1) Your incoming heater hose should be too hot to touch when the car is fully warmed up. If it isn't, then it would likely be the thermostat that is faulty. Of course it shouldn't be since it's been changed twice, but who knows what the quality of work or parts has been with the people you've been using.
2) The return heater hose should also be too hot to touch. If it isn't (while the incoming is too hot to touch), then that means your coolant is restricted when flowing through the heater core. So either it was never changed or it has gotten plugged up again due to poor work by the people you've been using.
3) If both heater hoses are too hot to touch, then it's your blend door.