The local shop owner is a great guy! If there is something the car owner can fix on the car himself, he suggest do it yourself, or he can repair it for a fee. But if it's not too labor intensive he explains the process.

My 89 420 SEL started having AC problems. sometimes when I started it the AC works fine, the next start no AC, for about a week. I figured low freon, but the shop owner says the AC freon is OK, and said he thinks the fan clutch is bad and that I can change it myself. When I check on the price it's $550 from MB and around $250 for aftermarket. He said the fan ran on after the motor was cut off. And without the fan clutch spinning the AC was cutting off.

Then I checked this board and found some posts saying the "Thermostat might be bad" resulting in the fan clutch switch might not be working properly, and the electric fan running too much.

The thermostat is a cheaper start in the fix than the fan clutch.