Vibration at Idle Only When the Air-Con Is On: Causes
A shake that arrives with the A/C button has a short suspect list. A Cranbourne West specialist explains.
What it usually means
The A/C compressor loads the engine; the ECU raises the idle to compensate. Vibration only with A/C on means either the idle-up isn’t happening (dirty throttle body, idle-control or software), the engine mounts are too tired to hide the extra load, or the compressor itself is rough and telegraphing through the car.
Mounts that are borderline all the time often reveal themselves the moment the compressor cuts in.
What you should do
It worsens on hot days in traffic — exactly when you want the A/C most. Diagnosis separates a cheap idle relearn from mounts or a compressor.
We watch the commanded idle with A/C on, load-test the mounts, and listen to the compressor cycle to pick the cause.
How we find & fix it
Because the same symptom can have several causes, we use dealer-level diagnostics and a methodical check to pinpoint the real cause — rather than throwing parts at it.
You get a clear explanation and a fixed written quote before any work. Book online in 60 seconds or call 03 8782 0711.
Vibration at Idle Only When the Air-Con Is On: Causes — FAQ
The compressor’s load exposes weak idle compensation, tired engine mounts, or a rough compressor.
If the idle-up isn’t happening — yes, a clean and relearn often settles it. We check that first.
The extra load rocks the engine harder — borderline mounts show up the moment the compressor engages.
A rough, noisy compressor telegraphs vibration — we listen to it cycle as part of the diagnosis.
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Car doing something odd?
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