75ZT Community

Please can anybody answer this?

When you switch the ECON button off, the A/C compressor runs and the fan starts. What else should happen?

Thank you

Mine reverts to Auto or whatever non auto A/C setting was last used. Recirc will also light up if temp high enough.

Sorry Mick, I meant what happens physically when you switch A/C on?

I've had a long running problem with A/C which was raised on here a while ago but I couldn't find the thread. I have now confirmed that the compressor runs, the fan runs, the pipes get hot and cold but there is no cold air to the cabin.

The compressor runs, turning the refrigerant from a gas (on the input) to a liquid (on the output). This makes the liquid hot, so it goes through the condenser to be cooled down. Its possible that actually it remains as a gas on the output and only liquefies as it goes through the condenser. In any case, a liquid, not too much above ambient comes out of the condenser in the high pressure line. This goes up to the evaporator, inside the heater unit. There's an evaporator valve with a small opening which allows the liquid to expand into the low pressure side, and it turns to a gas, going cold as the pressure drops. This makes the evaporator cold, and as air is blown through it, the air is cooled. The flaps inside can then send out this cooled air unheated, or heat it back up depending on the temperature setting and actual cabin temperature.

There's the rub Duncan The air entry flaps. I now remember from a previous thread that there was a possibility that they were causing the problem. Is this likely?

Its probably the least likely. Does the air blow hot all the time? If not then its likely they are working. Maybe the pipes are getting hot / cold, but not really hot / cold as they should be. You really need to know the evaporator temperature. Mind you, it doesn't always happen, does it? Maybe the flaps are sticking when its hot? There are separate temperature flaps for left and right, so if both sides aren't working they would have to be both faulty. Perhaps run the self test when its playing up: atc-diagnostics-t5659.html

Passes the self test Duncan, even when the fault is apparent.

Unlikely to be flaps then. Sounds like muck in the evaporator nozzle / valve is the last possibility. When you had the compressor problem a while back, is there a possibility that it let some bits of damaged metal into the system? What was the problem with it?

The compressor was replaced having siezed Duncan