Battery voltage drops

2012 DAIHATSU MOVE
110,000 MILES • 0.7L • 3 CYL • 2WD • AUTOMATIC
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FAHAD ANWAR
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Hi.
I connect and obd2 and cardoc android software for check battery voltage. When I drive my car without A/C my car run good but A/C on my car gets under power and headlights get little dim/fluctuate. I record my battery voltage with A/C on kindly check and suggest me what I do. And second EGR at idle shows 3.92 is it okay or not if it's not so it can be done by professional computer? I attached the screenshots.
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Aug 4, 2020 at 1:25 PM
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KASEKENNY
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I assume that when you notice the lights flicker is when the A/C is kicking on and off. This is going to be the same time you see the voltage drop.

I suspect the compressor or compressor clutch may be starting to lock up and when it kicks on it literally slows the engine or bogs it down and this will slow the drive belt which will slow the alternator for a split second. This will cause all other electrical loads to be effected which is why the lights are flickering. Further evidence is this doesn't happen with the A/C off.

Unfortunately we don't have a manual on your vehicle but here is a guide on how to replace a compressor.

If it were me, I would do this and then retest it. Based on this information, I am not sure what else could be the cause.

https://www.2carpros.com/articles/replace-air-conditioner-compressor

Let me know what you find and we can go from there. Thanks
Aug 4, 2020 at 2:25 PM
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FAHAD ANWAR
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Hi Kasekenny,

Compressor Denso sv07c.. I flashed the A/C system and checked the compressor. A/C guy finds it in a good condition no problem In compressor.
Aug 4, 2020 at 4:47 PM
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KASEKENNY
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Okay. The compressor may be operating properly but you are experiencing an issue when this is kicking on and no issue when it is not on. So while it may be operating it seems to cause this issue. How long have you owned this vehicle? Has it just started doing this or if you just bought it this may be normal for it.

Maybe get a video of what it is doing so we can see the issue. Thanks
Aug 4, 2020 at 7:23 PM
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FAHAD ANWAR
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I own this since 2017. it's not alternator fault or ground connection or battery (battery 2 years old) maintenance free battery
I am thinking to give a ground connection to battery with engine .
Aug 4, 2020 at 7:28 PM
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KASEKENNY
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You can do that. It won't hurt. Again, I am not suggesting it is the compressor is faulty or the alternator. What I am saying is that when the compressor kicks on, it actually slows the engine which causes the alternator to slow due to the belt not spinning as fast which will cause a voltage drop. Clearly we have a load issue due to this only happening when the A/C is on. This is what would make the most sense.
Aug 4, 2020 at 7:47 PM