Since you do not have heat, look at the servo first. That is mounted on the right side at the firewall with 4 heater hoses running into the bottom of it and a block of colored vacuum lines in the top. These are notorious to go bad and from reading on this forum they all go bad. My understanding is even Mercedes says it is a bad idea in these cars. You have one of two choices. Replace the servo with a rebuilt aluminum bodied one or go with an aftermarket solid state digital set up. Either way, prices are nearly the same but the solid state setup is more work to install, however, longevity is the key. A rebuilt servos life expectancy is unknown. Some last a short time, some last longer. Do some reading on this forum and you will find opinions on both. For me, I will be replacing it with the aftermarket setup that eliminates the servo. Here is the link for the one I will be purchasing. It comes with everything needed to do the replacement even though not everything is pictured. I talked with them the other day and the gentlemen I talked with was really nice and had plenty of information to offer. Good Luck!
Mercedes Benz Parts & Accessories - Mercedes 116 - CLICK HERE