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Last year my A/C was fixed. Then winter came. Then I had to buy a new car battery and so I went to a mechanic[1] who I paid to replace the battery with a new one.

My question is: When you replace a car battery, would anything in the A/C system be touched?

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I ask because the A/C was working very good before winter and before the car battery replacement and now the A/C does not work at all (air temperature feels the same as the outside air temperature). The car battery is the only work under the hood that has happened in between the A/C working and now the A/C is not working.

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[1]

The mechanic was one of those large mega-corp chains of auto-replace/auto-care. They did the repair late in the day after 4pm.

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  • You should probably mention what car you are using!
    – Bort
    Mar 9, 2016 at 2:34
  • @Bort 2008 Mazda 3
    – syn1kk
    Mar 9, 2016 at 2:35
  • I'd be interested to know if my solution below works for you.
    – Bort
    Mar 10, 2016 at 1:23
  • I'll try both yours and the refrigerant test (I bought a refrigerant pressure tester) tomorrow.
    – syn1kk
    Mar 10, 2016 at 2:27
  • Refer to your owner’s manual for how to operate the air conditioning system. If there’s an A/C switch in the cabin somewhere, for example, be sure it’s switched on. I just did a DIY battery replacement two days ago, and found the air circulation was no longer cooling air. When you take a battery out of your car, the electronics lose power; you may notice your clock and trip odometer have been reset, for example, and in my case my truck’s digital A/C switch was also reset without me noticing.
    – ADoofus
    Sep 28, 2019 at 18:26

2 Answers 2

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Nothing to do with the air conditioning would need to be moved or disconnected etc when replacing the battery.

However a refrigerant leak could occur at any time due to a number of reasons, with the most frequent being corrosion of the condenser at the front of the vehicle. Loss of refrigerant would cause total failure of A/C operation.

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I can tell you from experience that after losing power, certain vehicles will perform climate control calibrations when you restore power and start the car.

I had disconnected the battery on a Ford Fusion to replace it, and after installing the new battery and starting the car, the climate controls were completely useless. The temperature did not correlate to the settings whatsoever, and passenger side was different from the driver side, even though "dual zones" was turned off. Turning the heat/AC on/off and restarting the car did no good. My solution below worked, and I have to keep it in mind every time I disconnect the battery.

Solution:

  1. With the car off, unplug the climate control or "HVAC" fuse and wait 30 seconds before plugging it back in. Alternatively, you could disconnect the battery (in case you are unsure which fuse to pull or the fuse method doesn't work).
  2. After restoring power, start the car and do not touch any controls. Let the car calibrate the sensors. The wait period is arbitrary, but three minutes should be plenty.
  3. The climate controls should now be calibrated. Test both the heat and AC, and if available, test individual zone temperatures to be sure.
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