bohica2xo was spot on. I removed the blower motor and inserted the capillary tube into the evaporator and the compressor cycles normally.

Thanks for the tip. It is definitely not engaged in the evaporator. I will try to insert at a different angle.

I have a 1984 Mercedes 380SL (U.S. model). It still running R12. With the A/C on for more than about 20 min the evaporator freezes. No condensate drips from the drain tubes until the car has been shut down for about 10 minutes then there is quite a stream on the ground. The compressor does not cycle...