During heating in Auto mode it doesn't increase blower speed

[kejno]

Normal operation of AC when Auto mode is enabled and outside temperatures are low has following behavior: 

- when car is started cold then blower is set to minimum speed 

- once engine gets heated the controller increases blower speed to intensify heating of the interior because it can blow air now with higher temperature

- once temp sensor of interior signals it is warm enough controller decreases blower speed and reduces it to level to maintain temperature that is set 

 

All that was working properly, but since some time it started to misbehave and blower speed doesn't get increased when engine warmed-up. I need to either increase the temperature to 26C/78F or increase blower speed manually, and then later on reduce the temp. Pretty much 'Auto' mode is not working as it should, although heater core is delivering warm air. 

 

Anyone experienced that and knows how to fix it? I assume it might be interior temperature sensor fault or something connected to it, or maybe some settings? 

Do you know where temp sensor is located? 

 

Thanks!