If the heater hoses are warm to hot, the valve has failed open (no power) or the pushbutton unit is bad. If there is voltage on the monovalve when you want AC, but the hoses are hot, it's the valve. If no voltage, it's the pushbutton unit.

Either failure is pretty common. Monovalve on the W123/W126 can be fixed with a replacement valve, very easy (4 screws in a plastic housing, pull the valve out, put a new on in, put the xcrews bach in).

Pushbutton unit isn't hard either, just more expensive.

If hte suction hose is cold, the AC is working properly. Aux fan is a fuse for the current, probably over a relay. there is a pressure or temp switch on the receiver/dryer to switch the fan on, also a resistor in the fan circuit to run it a low speed, check the connections, they tend to corrode and cause a no fan condition.

If you run high side pressures that high, eventually the compressor will detonate or you will blow a hose, venting all the freon.

You must get the aux fan running, it will overpressure without it.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!