Huh. Sounds like you may have some other heating issues, because mine pumps out hot air after about 10 minutes of idle even when it's -10. It gets a little hotter when I'm driving because the RPM's go up. You should not need to go 20-30 minutes to just barely feel heat, especially if it's not even below freezing.
My first guess would be bad thermostat, but you already checked that. You may need a new heater core itself. Check the air-flow with different settings on your heater/AC controls, too. There may be a simple fix like a clogged air filter in there that needs replacing. Bottom line is that something ain't right, though. I get a lot of heat both front and rear on even the coldest days.
My first guess would be bad thermostat, but you already checked that. You may need a new heater core itself. Check the air-flow with different settings on your heater/AC controls, too. There may be a simple fix like a clogged air filter in there that needs replacing. Bottom line is that something ain't right, though. I get a lot of heat both front and rear on even the coldest days.