Climatronic exterior temp incorrect

Hi guys, I have recently bought a 2004 mk1 Octavia 1.9tdi pd 130hp it’s fitted with climatronic. I have found the exterior temperature on the heater panel and the instrument are reading anywhere between -12oC and +1 with the air conditioning being inop also. The ac is fully regassed with 750g, have replaced the ambient temp sensor behind the bumper and checked the wiring in the engine bay and under the battery ect all looks ok. I’ve got 5v on left and 0v and 3ohms to earth on the right. I’m assuming the ac isn’t cutting in as the car thinks it’s too cold. Has anyone had this? Climatronic unit? Instruments? Wiring? Help please