01 s4 heat problem

[Devious25]

My 01 Audi S4 heat barely works. The car rarely gets to normal operating temp. I can drive for a while and operating temp would be about quarter way. Sometimes it will go to normal but as soon as I turn the great on the cars temp will go down causing the heat to blow cold. I need some ideas on what to do here hoping I don't have to replace thermostat

 

[ex911driver]

Sounds like thermostat to me , if it is n`t getting to 90 and getting lower when moving.

 

[AndyC]

unfortunately its the stat.....you will need to change it...