Aircon on my Berlingo has been playing up since I've had it (it was old and cheap).
Some people in China I met on ebay have sent me Diagbox and an Authentic (?) Citroen diagnostics box and so yesterday I spent a bit of time trying to troubleshoot a few things.
For the aircon the issue is reported as a short-circuit to earth in the BSM on the control of the variable compressor cylinder (sorry - translating it roughly from French). I suspect that either said control is leaking electricity either at the compressor end (compressor needs replacing?) or the BSM has an issue (BSM R05) and the BSM needs replacing.
Any advice? I can pick up a second hand BSM for about 50€ here, so not a huge investment, but if the compressor is the issue then it's still money I could spend on something else.