Air Conditioner Cutout

From Citroen SM Wiki

In the SM fitted with Air Conditioning, the compressor is connected to the auxilliary shaft via V-belt. The absence of a high or low limit switch for the AC system has made the AC compressor a contributor to primary chain failures.

It is strongly recommended that a trinary switch be fitted. See also Air Conditioning. The switch is a hi/lo limit switch in one device. It will open on overpressure, it will open when the system is low on refrigerant.

Note: This will trap most problem modes however if there is a strictly mechanical failure and the system does not lose containment the switch offers no protection from the resultant load on the aux shaft.

Also, since the Air Conditioning compressor is engaged whenever the cabin fan is running (including in the heat position) it is advisable to install an Air Conditioning Defeat Switch so the compressor can be disengaged when not needed to save wear on the compressor and the chains. Simply wire a spare dome light switch across the connector to the thermostat (as shown below) and install in the spare position next to the rear defogger switch ('73 on). For <'72 you may need to relocate the ugly antenna control switch or install a fully automatic antenna wired to the radio.

Connection for Air Conditioner Cutout Switch - photo: John Titus