Problems with my Air con

[lee1boy]

Greetings chaps ,can you help me with a problem I have with my air con
Gas is ok,
relay works.
when i put a feed on the compressor  it works fine . when i intially turn on the the system it works for about 20 seconds then cuts out.
I think this implies that the thermostat is not working.
Has any body elese had these problems and what did they find.
Regards Lee
:wave