Idle Speed With Ac

[BigMo82]

I have been having problems with my idle dropping to 600rpm once the car warms up to normal temperature. When I turn the AC on the revs rise to about 800 for 2 minutes but then drop back to 600 again. I know it's normal for the revs to rise when the ac is switched on but should they drop back after a few minutes? Any help or advice is appreciated.

Mo

[Konrad C]

Hi Mo,

It depends on the ambient temperature and the cabin temperature the system works with.

If it is a hot day and the cabin needs to be kept cool, then the air-con has to work hard to keep the cabin cool. Once it has reached it's target, then the air-con cuts off. The engine compensates for the load imposed by the air-con.

It has not been that hot so I guess your air-con has not worked hard to get to temperature.

I used air-con over the last weekend and it kept the car cool and the engine load was light. Idle stayed nearly normal with the occasional rise when the air-con kicked in for a few minutes.

the other thing you need to be aware of is if the system needs re-gassing. If it cools well then you should be okay.

Mine was last re-gassed about 5 years ago and it works quite well. I do use it during the winter to clear the screen, plus when it rains to clear the windows. This keeps the system sealed.

[BigMo82]

Thanks for the reply Konrad. I didn't think of it like that. I was under the impression that the increased rpm should stay that way until the ac is switched off. Just trying to work out if the problem with my idle is the Battery, alternator, ignition coils, sparks or something else! Lol

Mo

[Roker]

With the AC on, my RPM constantly speeds up and drops as the radator fan starts and stops, as long as it does not stall do not worry