Hi Pat,
The wiper linkage is fitted to a motor located behind the glove box. The motor can be removed by unbolting the linkage and then unbolting the motor from the engine compartment. The linkage is connected to the motor arm by a single(10m?)bolt. It may be accessable without removing the glovebox but I'm not sure.
As the motor arm spins the wiper linkage pivots in a couple of places under the dash. If the motor isn't frozen I don't think your problem lies in the area. In addition to the under dash wiper pivot pins the linkage spins CW and CCW via the wiper shafts which extend through bushings in the body below the windshield. More than likely this is the area where the binding has occurred. I suggest you remove the wiper arms and spray penetrating oil in the wiper shaft/bushing area to see if you can free up the binding. The entire wiper linkage assembly can be removed if you take the gauges and other under dash components out. It's a pain to do. After the penetrating oil has had some time to work you should be able to move the wiper linkage from below the dash by hand or via the wiper arm on the shaft outside the body.
Jeff C.
1970 280SL 4-speed
