A/C and Heater battling it out...

[atatexan]

Excellent article and responses. Have this issue on my 350SE. The problem slowly got worse in a way my tech thinks is a valve vacuum problem: under heavy acceleration the heat would mysteriously come on overpowering the A/C for a few minutes. Now it is total air temperature war. My guy says M-B was very worried about hypothermia in the event of a system failure. My temporary fix is to tie off the heater valve arm (rt. side firewall location) to stop the war at least for the summer.