Air con problem

Hi all,my air con stopped working a few days ago.I have found the problem,there is
no voltage at the compressor end.Does anyone know where this wire originates from
so I can check if the wire is broken,or if its something more sinister.
Many thanks in advance.

 

compressory doesn't ever run all the time, right? Could be just low on freon, which would never allow the compressor to get turned on.

 

The wire gives power to the magnetic clutch.It is not clicking in on my car,but when I connected a battery directly to it it did.

 

Besides the switch that turns it on, there are low and high pressure cut out switches in the front trunk attached to the receiver/drier that have to be closed for the system to work. This is all fed by relay 99 (?) that is controlled by the thermostatic switch in the center console. Assuming you have a 308 variant... not having any information on your profile or mentioning the car this is on makes any more help a bit difficult.

Rick

 

Oops I have completely forgotten about all that stuff.My car is a 1979 308GTB.
Thanks for that Rick, it gives me much more to look at in the morning.