22 Corolla LE CVT AC on/ idle up and down

[Divers89]

Hey guys, just purchased a 22 Corolla SE CVT. I noticed on the way home while my wife decided to go through the Popeyes drive through that with the AC on while stopped the RPMS like to go up every 5-10 seconds then back down. I hear the fan kick on and that’s when it goes up. I checked with the hood open as well. Fan rotates faster and causes the RPMs to go up. Is that normal? Is it just the programming? Car only has 29k miles.

car won’t do it with AC off.

anyone experience this or can confirm normal? I’m assuming it’s normal? 

Took a video of this with the AC on and this is what it does

 

[yossarian247]

We don't get that engine/gearbox combination in the Corolla in the UK, only hybrids now, but I've owned other Toyotas that did exactly what your car is doing and it's perfectly normal. 

[Divers89]

Okay cool! Yeah kinda just freaked me out a bit because the idle will go up and then back down and then back up while the AC is on pretty frequently. Crazy lol.

[TonyHSD]

It’s normal 

[Divers89]

Thank you guys! Wife was freaking out lol

[AndrueC]

I would assume that the RPMs increase when the compressor switches on.

A/C systems do not run continuously. They operate like a fridge (which is essentially what they are of course) and the compressor switches on/off as needed. If the cabin temperature is what the occupants have asked for the compressor isn't needed and only the fan will be running (possibly at a lower rate).

When the compressor kicks in the fan might also increase in speed to push the resulting cold air into the cabin more quickly.

Whatever the source of power for the A/C is will have to work harder. On a hybrid system the A/C is powered from the traction Battery which can often meet this demand without further help.

But in a conventional car the ICE is going to have to work a bit harder either to increase the rate of charge of the 12v Battery or perhaps because the compressor is running directly off the ICE via a belt.

[Cyker]

Yeah the AC compressor can add a 2-3kW load to the engine and petrol engines need to spin faster to provide that extra power. With AC compressors that cycle on and off, the engine will speed up and slow down too.

It's one nice thing about hybrids and diesels as they are less noticeably affected - Hybrids and EVs power the AC compressor with a high-voltage electric motor, and diesels have so much excess torque the rpm barely changes  

[yossarian247]

13 hours ago, Cyker said:

Yeah the AC compressor can add a 2-3kW load to the engine and petrol engines need to spin faster to provide that extra power. With AC compressors that cycle on and off, the engine will speed up and slow down too.

It's one nice thing about hybrids and diesels as they are less noticeably affected - Hybrids and EVs power the AC compressor with a high-voltage electric motor, and diesels have so much excess torque the rpm barely changes  

I've find it very noticeable and quite annoying when I've driven Aygos in the past. With the engine idling and the AC on, the small petrol engine continuously needs to rev up each time the AC compressor cuts in. 

[AndrueC]

4 hours ago, yossarian247 said:

I've find it very noticeable and quite annoying when I've driven Aygos in the past. With the engine idling and the AC on, the small petrol engine continuously needs to rev up each time the AC compressor cuts in. 

I suppose that's why A/C was uncommon on smaller engines back in the day.