hello for 3 months have bought a s500 w220 ez 06.99 jetz I have the problem that after about a half hour driving time it gets cold in the car and the temperature cannot be kept it comes as good as no airflow from the air nozzles even if I manually to max place increases the audible heater blower but it no longer comes airflow from the nozzles and from time to time the little air which comes out also cold who can help me in advance already best thanks