If I am to expect +12v to the a/c compressor can anyone advise what pre-requisites need to be met. As a starter I am only aware of the following:- A/C light ON on control panel 30A fuse intact High pressure regulator switch closed (where is this ? ) (on the drier ?) Low pressure regulator switch closed (where is this ?) Is that it ? Does the outside air temperature sensor have any effect ? (located on blower ?) Is the +12v switched via a relay - if so which one. Does anyone have the wiring diagrams ? Apologies for all the questions but I am trying to systematically diagnose why it doesn't work. By knowing the above I may be able to bypass areas of the system to eliminate certain elements. Thanks in advance John
The single most common cause of not working is low gas. When gas pressure drops below a certain presure, the hi/low pressure switch cuts out. Cars vary here, but most 348 have a combined hi-lo switch. It's under the front carpet panel and has 4 wires coming off it mainly a blue/black theme, on the side of the receiver dryer. Bridging the low pressure part of the switch will re activate the system, and it'll probably work to some extent. Pressure can drop off for any number of reasons, natural wastage being the most common. However, if you really care for your car, and get regular dealer/specialist services done, the gas will be checked and topped up every 2-3 years unless faulty. With 348/355, whenever the engine is removed for belts service, the A/C gets re-gassed anyway. By far the best approach to A/C is to leave it to someone with the equipment to service it. It is potentially dangerous. There are very high pressures, toxic gases (especially if burnt through a gas heater) and danger of frostbite if messing with connections of hoses.
Phil, Thanks. The system was re-gassed and pressure tested in Feb this year during an 18K engine out service but the A/C still did not come on. I have seen the connector you refer to - do you know which pins I should check to see if the high/low pressure regulators are 'switched in' I do not plan on removing any hoses Thanks John
