Civic diesel MK8. - New battery and voltage

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Wed 30 Jul 2025 14:51
Civic diesel MK8. - New battery and voltage - Surreydriver

Old battery had died,11.6 V and unable to charge ( 5 years plus old). New battery installed. At terminals out of the box it read 12.9V and in car with leads attached ( but not switched on ) 12.85V. Should I be doing a parasitic drain check ? I omitted to check terminal volts with the engine running, but alternator light went out as usual. Battery is correct 74AH 680AMP. Pointers appreciated. Thank you.

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Wed 30 Jul 2025 15:02
Civic diesel MK8. - New battery and voltage - elekie&a/c doctor
I would do a charging Voltage test at the battery with engine running before considering and other issues.
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Wed 30 Jul 2025 15:05
Civic diesel MK8. - New battery and voltage - Surreydriver

Thank you Doctor. Will do.

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Wed 30 Jul 2025 15:19
Civic diesel MK8. - New battery and voltage - Surreydriver

Appr 14.2 to 14.4 V from idle to 2k rpm. Switched off, 13.4 slowly reducing to 13.1 V over a couple of minutes.

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Wed 30 Jul 2025 15:19
Civic diesel MK8. - New battery and voltage - daveyjp

Plug in voltmeter £6 from Amazon. Stick it in the cigarette lighter and you will be able to monitor any fluctuations, charging level etc.

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Wed 30 Jul 2025 16:01
Civic diesel MK8. - New battery and voltage - elekie&a/c doctor
Those voltages all look fine to me
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Wed 30 Jul 2025 17:55
Civic diesel MK8. - New battery and voltage - Surreydriver

Thx for input. Cheers.

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Fri 1 Aug 2025 12:08
Civic diesel MK8. - New battery and voltage - Steveieb

I had the same experience with my E W211 .

New battery , voltages fine checked by auto electrician but the battery warning light kept coming on shortly after starting.

Took it to the MB specialist who diagnosed faulty alternator, which was replaced and fine since. Maybe the regulator was playing up ?

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Fri 1 Aug 2025 12:20
Civic diesel MK8. - New battery and voltage - Surreydriver

Possibly, I hope not, and testing output seems OK (as above). In my case the battery voltage was very low (as above) and it simply would not accept a recharge - and the charger got really hot and the indicator lights did not indicate all was well.

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Tue 5 Aug 2025 10:21
Civic diesel MK8. - New battery and voltage - Surreydriver

FWIW it was fuse # 16 and the HFT module. Removed ( and hot to touch ). Apparently EX trim models are notorious for it causing parasitic drain. ( Courtesy of Civinfo.com).

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Tue 5 Aug 2025 10:30
Civic diesel MK8. - New battery and voltage - elekie&a/c doctor
Battery drain caused by the Bluetooth module is a very common issue across all Honda models , including the Accord .,
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Thu 7 Aug 2025 01:58
Civic diesel MK8. - New battery and voltage - edlithgow

I had the same experience with my E W211 .

New battery , voltages fine checked by auto electrician but the battery warning light kept coming on shortly after starting.

Took it to the MB specialist who diagnosed faulty alternator, which was replaced and fine since. Maybe the regulator was playing up ?

That doesn't sound like the "same experience", since the OP did not, up to that point, describe evidence of any problem, apart from his original battery failure, which could reasonably have been attributed to simple old age..

Its unclear whether the later mention of the HFT module relates to that failure or was still an ongoing issue after battery replacement, but presumably if it was its been resolved, perhaps by throwing the b***** thing away.

Edited by edlithgow on 07/08/2025 at 02:12

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