Re: climate control randomly changing
I presume you have the manual airconditioning system? The defrost position is the failback position when vacuum is lost. The manual system is using vacuum on all exept the temperature control actuator. I would check the vacuum lines from the engine inlet up to the firewall to check for chaving or other damage. The problem also could be in the switch, so if looking under the hood didn't reveil anything, i would remove the mode control vacuum switch and see the lines behind there. I can imagine that when the vacuum is weak due to a chaved line, that the vacuum actuator has less force to keep the mode door in the requird position.