Preemptive replacement of mono valve on '87 300SDL

[airfoill]

Hello to the group. My car is a '87 300SDL. I had another link earlier last month regarding a problem I was having with my Climate Control Unit which I was able to fix.

300SDL Climate Control Clicking When Cold Outside Temperature

I wanted to ask this on a specific thread regarding the mono valve. I am the second owner of the car and don't know if the mono valve has been ever been replaced. The car only has 120,000 miles on it.

I know the mono valve is working properly and have tested it. However, I have learned on this forum that if the mono valve shorts out, it can also short out the CCU. I was inclined to replace the mono valve just to make sure its as new as possible and head off any future potential shorting issues regarding the mono valve. The only issue I'm having is where does one get the new mono valve cartridge? The ones that have been sold on this site are supposedly not the greatest quality and aren't like the original units. Where do you get the best quality mono valves?

Thanks

Herb