Car is a 1995 E420 and I've been having to hunt down a popping/ticking sound from inside my dash for the past few months and have finally found the culprit. The heater control valve on the passenger side. When it's active, it ticks/pulses every 4-5 seconds constantly as long as the heat is on in the car. This noise is transferred to the cabin and is very audible. Anyone have any insight into what the problem could be. I always thought the ticking of the valve was normal operation. My guesses are that the valve is simply louder than it should be (replace) or that its operating too often (either the valve itself or the CCU). Any feedback would be great! Thanks!

__________________
1995 E420
1998 SL500 Sport
2009 E350 Sport
1995 S500 Coupe
1992 500 SEL