I have a 2003 CLK 430 convertible and the top will not go down. A mechanic checked it and said it was a faulty limit switch.

It could be. It also could be the hydraulic pump. It could be a fuse. It could be a window fault.

Does anyone know how to find and replace a limit switch? I believe there are 3 separate switches, how do you determine which switch is faulty?

1. There are many more than 3 limit switches.
We have a forum 'Sticky' section that remains at the top of all the daily posts. These are important threads that include C209 Maintenance, DIY, etc. If you check the thread titled 'W209 CLK Maintenance' you will find lots of information on the cabriolet soft top problems. This one deals with the soft top limit switches:
http://www.benzworld.org/forums/c20...g/forums/c209-a209-clk-class/1621984-soft-top-circuit-diagram-limit-switch.html

2. You could get your soft top fault codes read, which should direct you to the right area.

3. Welcome to the C209 forum. We have lots of experience here, and try to help when possible.

 

2003 CLK430 is a W208 - you might get better help and info from that forum.

 

Aah - so it is.

The fault codes should be valid, I think.