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I recently noticed that my car had the issue starting without giving it a boost. It has original battery and has 155k on it.

Over the course of 2 weeks I realized below two things which helps car start without much issue (sometimes I've to try 2-3 times but no need to give boost):

  1. Pressing accelerator 25% and starting car works for some reason.
  2. I need to turn off Radio and AC before turning off the car for the car to start properly next time. This helps battery from dying for some reason when I want to start the car next time or maybe battery has enough power to start the engine only and it doesn't have to work to start AC and Radio?

I went to 2 different mechanics and both of them said different things.

  • One said it's a starter issue and maybe battery needs to be replaced as well.
  • Other mechanic said the battery is little weak but it is still fine, no starter issues and seems like some kind of electrical issue.

Did anyone face the similar issue or any insight if it is battery, starter or alternator based on the issues described here?

  • When the car gives you starting trouble is it eventually starting ? - is it cranking like normal or is it cranking slowly? What year make and model car? – mike65535 Jul 9 '18 at 19:35
  • If I followed those 2 steps (accelerator 25% & turned off radio, AC during after previous use) it does eventually start. First 1-2 cranking could be slow if it doesn't start then it starts with normal cranking. – Connect The Dots Jul 9 '18 at 19:46
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    Any battery with that many miles on it is likely past its normal lifetime. I've had two mechanics differ on the state of the same battery - one saying it was "OK" and the other saying "no way". – mike65535 Jul 9 '18 at 19:49
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    I'd go with replacing the battery, anyway ... as long as it's over 5 years old. It is conceivable the car is under 5yrs and has that many miles on it, though I don't think I could fit those many miles on one in that amount of time! :o) If you know something is weak (or bad) start with replacing it and go from there. – Pᴀᴜʟsᴛᴇʀ2 Jul 9 '18 at 20:35
  • Btw, I forgot to mention car make and model. It is 2010 Hyundai SantaFe. It has 155k km = 96k miles on that same original battery. – Connect The Dots Jul 10 '18 at 13:28
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Any lead storage battery is suspect after five years. Testing the voltage is not a very effective way of determining the reliability of a battery, since it is the amperes that really crank the engine. I've owned cars in the past that seem to have mysterious, minor electrical shorts somewhere in the electronics, but replacing the battery completely resolved the issues.

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Test your battery. A standard 6 cell battery should be around 12.6 volts. There may also be a short somewhere causing your battery to drain prematurely.

If you replace the battery without finding the issue, you'll might destroy the new battery as well.

  • I tested this at home and battery was around 12.8 volts. At mechanic it was 11.1 (mechanic who said battery is weak but still he thinks there is some electrical issue). Also, at other mechanic it was close to 12.6 but he said after some load test battery lost some power. – Connect The Dots Jul 10 '18 at 13:42
  • @ConnectTheDots, based on the 12.8v and 12.6v readings, the battery should be ok. However, the 11.1v reading suggests that it is bad. And given that the battery is 7+ years old, it is near the end of its life. Get a new battery, but keep the old one. If the new battery does not fix the problem, re-install the old battery, as Henry suggests. Once you fix the problem, the store you bought the new bat from will pay you for the old bat. This popular auto part store in the USA explains how this works. It is probably similar where you live. – Sam Jul 10 '18 at 22:49
  • Ok, so I tried swapping the battery with another car which has an exact same battery. After swapping the battery other car worked fine but not my car so I was able to rule out that it is not a battery issue. I guess I will have to try replacing the starter. – Connect The Dots Jul 15 '18 at 17:44
  • Good follow-up. Have you considered a short in the a/c? I actually had a car decades ago that had an electric a/c clutch and its plastic electrical connector cracked, draining my battery overnight. You can easily disconnect those plastic electrical harnesses under the hood and check for cracks. – Carguy Jul 15 '18 at 20:23
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To conclude this I had to replace the starter to fix the issue. Here is what I learned and how I ruled out the problem:

  1. Faulty car was not starting so I swapped the battery with my another car which had exact same battery. After swap another car started fine with the same battery (Faulty car did not start before battery swap & even after) so I was able to conclude that battery is fine as well alternator (battery charging system) is working fine.
  2. I went to mechanic who said it was a starter problem, he replaced the starter and car is working fine.
  3. Interestingly after the car starter was fixed in couple of days I forgot to turn off the lights on that car and car wouldn't start. When I try to start the car. Starter goes 'ta... tata... ta... tata...'. (Now I know how starter sounds... haha :). I was able to tell right away that battery needs boost and I had to jump start the car).

Since then car is working fine!

  • glad you got it fixed. For future reference, when your car is in "crank" position, it doesn't matter if any accessories such as radio are turned on. The crank position does not send power to them while the car is cranking. – John Lord Aug 3 '18 at 15:31

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