When I turn on the A/C, the car jerks when idling?

Tiny
DHWANIL123
  • MEMBER
  • 2005 NISSAN PULSAR
  • 1.8L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 181,407 MILES
Also, when the car is idle or not moving A/C gives cold air, but while moving, the A/C gives hot air.

What could be the problem?
Monday, March 6th, 2023 AT 6:25 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Are there any odd noises from the A/C compressor? Also, the idea that the engine jerks may or may not be normal. When the compressor engages, it places a heavy load on the engine. Oftentimes, you will feel it. Could that be what you feel or is the jerk excessive?

Next, if the AC doesn't cool while moving, it may simply be low on freon. Here is a link that explains how to charge/add Freon. I would try this first unless there is a strange noise when the system is on.

https://www.2carpros.com/articles/air-conditioner-how-to-add-freon

Let me know what you find or if I can help in any way. Also, let me know if you are hearing any noises that don't seem normal.

Take care,

joe
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Monday, March 6th, 2023 AT 9:04 PM
Tiny
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Hey, I don't hear any noises, but the jerk is like the RPM is changing and giving a small jerk if the A/C is on.
Also, I went to a mechanic, he said there is no problem in the A/C, since the A/C gas is full.
He said there might be a problem with the vacuum switch valve.
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Tuesday, March 7th, 2023 AT 2:28 AM
Tiny
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Hi,

If I had to guess, what you are experiencing is normal. Keep in mind, once the A/C is on, the compressor cycles on and off. I suspect that is what you are feeling.

If you can, record it so I can see the tachometer and how the vehicle is reacting with the AC on.

Let me know.

Joe
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Tuesday, March 7th, 2023 AT 5:32 PM
Tiny
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This is the problem, that race problem is even when I drive, but less with A/C off, A/C on increases that problem.
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Thursday, March 16th, 2023 AT 10:41 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I watched the tachometer and listened to the engine speed. The two didn't mirror each other. The tachometer is jumping but the engine speed doesn't change. Is that correct?

Please understand that I am listening to it through a small speaker on a computer. I realize I could be wrong, but the engine sounded very steady. I would think the tachometer itself or a connector to it may be the issue.

Let me know.

Joe
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Friday, March 17th, 2023 AT 7:35 PM

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