I bought the car in the summer and never really used the heater, but it was a bit cooler today so I had the heater on and it doesnt get very hot even with the climate control set at its highest.
I replaced the t-stat and coolant today to get ready for winter but still no difference in heater temps. Is there something else I should be looking at?

The car has never overheated on me so I dont think its an airlock or blockage. Could there still be some sort of blockage somewhere?

 

Blocked heater core perhaps. Two heater hoses go into firewall to heater core, after warm up one shoud be hot the other cooler if you are getting circulatrion.

 

Do both heater core hoses go from the tee to core or does one come from the water pump?

 

So I figured out the hoses and instead of disconnecting the outlet hose underneath I just disconnected the heater inlet and the bypass hoses from the tee/restricter and looped a piece of 3/4" hose on the open fittings of the tee. Then connected a garden hose to the bypass hose, (old cut garden hoses with splice fittings are useful to keep around) Left the inlet hose open and turned on the water to run through the core opposite of normal flow direction. Took a minute but it started pushing out brown crap then clean water. I shut the water off, let it sit for a couple minutes and then flushed again, got more brown water. Did it a couple more times till no more brown crap then switched hoses and flushed the other way. Everything clear I reconnected the hoses to the tee and ran the car to get everything flowing and make sure there was no air in the system. So far so good and I have heat.
Hopefully it lasts and I dont need to do this again anytime soon, like first cold snap.
Now to get my coolant to the proper mixture........

Thought I would update with a description of how I did it just in case anyone else has this issue and needs a simple way to flush the core.
Sorry for the long post.