Noise coming from Climate Control Unit
 

Yesterday while I was drivng with A/C on, I heard some strange noise coming intermittently on and off from the climate control push button unit.
Any body has any idea what was it?

Thank you

Steve
1985 300D

Hi Steve, if you heard hissing noises you may be a bit low on refrigerant. When this is the case the flow can be heard when the expansion valve opens and closes.

Thanks for the reply.
It is not exactly hissing noise. It is sort of like something is shorting out noise. The A/C works fine, I do get very cold air coming out from the vents.

Sounds like one of the switchover valves. They control the vacuum for the ACC system. It also uses electricity to work, that is what you usually hear clicking. They are located behind the push button assembly just to the right. You can put your finger on the one that is clicking.