A/C compressor not engaging

[DavidS]

The a/c on my 2014 GT 200bhp stopped working. The light on the button will still light/go out on a press, but the compressor doesn't seem to engage. I've checked the system is fully pressurised. It looks as though the electric clutch is not being picked. I haven't been able to get access to check if there is a voltage across the wiring at the compressor when pressing the button. I don't want to invest in a whole new compressor unless it is actually broken. Only other information is that I think the a/c stopped working when the engine overheated (plastic hose failure) but I can't be certain. Everything else runs fine and no other electrical problems. Any ideas?

 

[Pedro]

My faulty thermostat stopped mine (engine temp stopped just short of 90) which made me suspicious so had the gas checked & noting wrong decided to change the thermostat tank as its not uncommon for this unit to cause havoc with the cooling-heating A/C system by sending faulty data to the ECU & fault was actually cured so don't overlook the fact that the engine temp is not linked to A/C not working?

 

[DavidS]

Thanks Pedro, is there is a sensor on the thermostat housing then?
Just re-checked my engine coming up to temperature, sat idling. The analog dashboard temperature gauge goes up to 90 within 15 mins. The ECT (Engine Coolant Temp?) live data through the OBD2 port lags behind the analog display, but eventually shows 90 degrees (after about 20 minutes). I'm pretty certain the ECT value must be passed by the ECU to the OBD2 port? To me, that implies that the temperature sensor is operating correctly. Could there be more than one sensor?
Even when up to temperature, turning on the AC only shows an amber light on the button, but nothing else happens and there is no dip in engine revs. It doesn't feel as if the compressor clutch is being picked? I'm wondering if the amber light on the button is confirmation that a voltage is being applied across the compressor clutch?

 

[DavidS]

I did a little more digging. The live data for the digital ECT value lags behind the analog temp display, but eventually goes up as high as 106C. The analog display never shows higher than 90C on the dashboard. Bottom line, I think the ECU should be getting accurate temperature data.

 

[DavidS]

So I got this resolved in the end. Thought I'd detail it just in case this helps someone else to diagnose a problem. The RCZ uses the old style refrigerant gas, and whilst my system was properly pressurised, the air con never cut in. It turned out that the bearings in the compressor were seized, so it took a new compressor to make it work. Also, when the mechanic sucked out the old refrigerant he found that there was no lubricant in it. Apparently when filling the refrigerant you must add in lubricant as it is this that keeps the bearings working. I suspect the previous owner had a leak and had it refilled, but the garage didn't put any lubricant in, leading to the bearings seizing up over time.

 

[lfe]

The RCZ's air conditioning compressor doesn't have a clutch, it always spins, like in many other modern cars.

It uses a variable displacement compressor, and a solenoid valve regulates the amount of compressed gas.