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Hi all,

Hopefully this is the right subsection, as I think my question may relate to a few different issues.

Searching through the forum, it seems that most problems people face is when the AC is turned on, the RPM drops really low, on the brink of stalling.
Mine seems to be the complete opposite. When I push in the AC button, my RPM's climb to ~1100. Normal idle is ~800 RPM.

I did not think the RPM's were meant to change so drastically as well.

Ever since I bought the car in August last year, it has been like this, and I thought the RPM rise was relatively standard until reading other posts. The car has needed a regas since purchase, and I am hoping to make sure the system is at least working before getting that done.

Hopefully someone knows what may be going wrong here.

Nope that's normal, its the ECU telling the car to idle up to prevent stalling. If the idle drops low, that means its not working properly.

The engine will idle up when the compressor is cycling, and turns off when the temp sensor in the evaporator core reaches a certain temp, in which then it will go back to normal idle.

If your aircon is out of gas, it should always cycle as it never gets cold enough to trigger the temp sensor and turn off compressor and hence turn off the idle up.

Thank you so much spikes. Gives me a little peace of mind when I get it regassed it will work.

If you get quoted like a billion dollars to do a R134a conversion, look into Hychill Minus 30 conversions, they work quite well as an cheaper alternative and don't need much work as R134a.

But before you get it regassed, make sure the expansion valve (or known as a TX valve) is working properly, it regulates the flow of refrigerant through the evaporator, if it's stuck close or open, the refrigerant won't be expanding in the right place and you won't have a properly working aircon.

But any decent auto electrician should be able to determine if there's any faults. If there's still gas in the system, the high and low sides should read the appropriate pressures when the aircon system is operating.

Hychill HR12 is the direct replacement alternative for the old R12 system.

No change in the ester/mineral oil needed, just get the auto electrician to do a leak down and pressure test, and then refill. From memory, 220 grams is needed (larger molecules compared to R134a, so less gas is needed).

My system behaves the same as you described, so totally normal.

Thanks for all the replies