S series AC troubleshooting

New to me used 1997 S1 series.
outside air temp a little above freezing (~10C) and engine warm
AC inoperative
cabin fan on high
light in dash on when AC switch pressed in
light in dash on when recirc switch pressed in, air valves operate correctly
AC compressor clutch does not engage
AC compressor drive shaft can be turned easily by hand
the rad fan is off
checked 10A fuse OK

system line pressure switch is in closed position
IS THIS SWITCH NORMALLY OPEN OR CLOSED?

when system line pressure connector is removed, the AC clutch compressor
does not engage.
when system line pressure connector is jumpered, the AC clutch compressor
does not engage.
when power is applied to AC clutch connector, the clutch applies and
compressor turns normally with no bad noises.

I suspect damage to condenser? rad mounted in front of engine coolant red
has caused loss of refrigerant pressure, but am puzzled by failure of
compressor fan to engage when low pressure connector is jumpered.

Help please.

 

I suspect that this switch will/should be open when pressure is low and
closed when pressure is good, but are some systems reversed?

 

This car seems to be switched closed when pressure is good.

A little time and some more testing and the system now seems to be
functioning correctly. One of the online manuals said that the system would
not function unless the temp was high enough so I let it run at a fast idle
long enough to cause the rad fan to engage and cycle normally. I swapped
the relays to check that both were functioning correctly and then the
compressor clutch engaged when I jumpered the low pressure connector.
Reconnected everything and it seems to be functioning properly. I suspect
that if I had been doing this test in the hot weather that I would not had
any problem.