Considering '89 300E -- What To Beware Of?

[Abner Mality]

I am trying to aid my widowed cousin in the purchase of a used 1989 300E. This particular vehicle has only 152K miles, and appears to have always been garaged. There isn't even one shopping cart ding on the exterior, and the interior is very clean: dash wood is excellent. seating surfaces show very little wear, etc. The only issue I could find, during a short test drive, is that the A/C fluctuates from full on to barely blowing any air. The system is exchanging heat as the air from the vents is nice and cold, but the fan will not run full blast all the time. Also, it seems that the problem might be vacuum related because the fan blows good on acceleration, but drops to low speed when one lets off the accelerator. That actually sound bass ackward to me, vacuum wise, but I tried several time, and for the most part the more acceleration, the harder the fan blowed. Any suggestions?

While I'm at it: What are some of the common problems with this model Benz?

Oh, and the asking price is $3150. I'm considering an offer of around $2400 if the A/C issue can be corrected by the dealer.