The R15 may still be located under the brake booster (covered with leaves) and the F22 is probably located on the booster side of the firewall (1 1/2" by 1/2" black plastic fuse block bolted to the back side of the aluminum firewall partition). The fuse box looks like this.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1985-Mercedes--Benz-500sec-Body--Electrical&yearid=1985%40%401985&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6291%3AMBC%7C1540%3AED%7C10000058%40%40500SEC&catid=241959%40%40Body+Electrical&subcatid=241968@@Fusebox&mode=PA

Mark