Eratic idle with a/c on.

[Archie0979]

I have this issue when my car is idling with the a/c on that the revs jump about from about 950 rpm - 1050 rpm. I only get this erratic idle when the a/c is on. If I turn it off my revs drop just to above 800 rpm and holds solid as a rock. I have no error codes and apart from the above issue the car runs like a dream. Has anyone experienced the same issue and/or know what is causing this? I know my aircon needs recharged as it no longer blows ice cold air but I didn't think this would be the problem? 

[furtula]

Car auto adjusts the RPM's to accommodate the additional load created by the AC. It does the same when you turn on the lights for example, as it creates additional load.

[yossarian247]

Yes as above its perfectly normal. The AC compressor cuts in and out according to demand for cold air, and each time it cuts in the engine revs increase slightly to compensate. When it cuts out the revs drop again.

[Archie0979]

Thanks for your replies guys. After doing a bit more research I have also came across an article that say's if your a/c has a low charge of gas this will cause the a/c compressor to enter a state of constantly switching itself off and on which will cause revs to jump up and down at idle. This would make sense as my a/c system definitely needs to be charged again.

[yossarian247]

On 2/8/2020 at 12:39 AM, Archie0979 said:

Thanks for your replies guys. After doing a bit more research I have also came across an article that say's if your a/c has a low charge of gas this will cause the a/c compressor to enter a state of constantly switching itself off and on which will cause revs to jump up and down at idle. This would make sense as my a/c system definitely needs to be charged again.

Perhaps, but that is normal on Toyotas. They operate the compressor on a duty cycle of continually cutting in and out, it is how they regulate the output of the AC system. Only in very hot weather should the compressor run continously on these, and even then once the temperature of the interior reaches the desired level the compressor will revert to cutting in and out every few seconds. Both our Auris and Avensis have done this all the years we've owned them and neither is low on refrigerant.