OEM Positive Engine Terminal Electrical Issue

aisthetes · 08-16-2023, 06:00 PM

I’ve had my M3 coupe for two years now, and keep it on a Ctek battery tender. Out of the blue, over the weekend the OEM positive terminal (with the red cap by the coolant tank) seems to be staying electrically charged when the car is shut off. I can no longer attach the red Ctek alligator clamp to the positive terminal without loud pops and sparks flying. It’s actually pretty scary. The car is off, key removed and alligator clamps are not even plugged into the Ctek. Has anyone experienced this? I’ll take some good theories, too!

Thanks,
Doug

amrazM · 08-17-2023, 05:19 AM

where is the negative connected?

aisthetes · 08-17-2023, 05:33 AM

To the factory negative post in the engine bay. I can’t even get that far. The positive pops and sparks first without the alligator clamp plugged into power.

charliev68 · 08-17-2023, 06:17 AM

Get a Meter and probe that terminal! See what voltage it is putting out.

aisthetes · 08-17-2023, 07:54 AM

So I had an inexpensive electrical tester shipped last night. The positive terminal had low voltage going through. One bar on the meter with a slow beeping sound. An electrical wall outlet has two bars and faster beeps.

I checked it again this morning. By now the car hasn’t been driven for three days. No beeping at all. I bought new Ctek alligator clamps to rule that out. No sparks at all and the tender is plugged in working fine again.

So it seems like suddenly the positive terminal is holding a charge for a period after the car is off. The last two years I could charge it right away never with a spark or issue. Could this be a random power surge? Maybe issues with the battery slowly failing?

08-16-2023, 06:00 PM	#1
aisthetes First Lieutenant 13 Rep 340 Posts Drives: 2013 M3 Competition Join Date: Sep 2008 Location: Colorado iTrader: (0)	OEM Positive Engine Terminal Electrical Issue I’ve had my M3 coupe for two years now, and keep it on a Ctek battery tender. Out of the blue, over the weekend the OEM positive terminal (with the red cap by the coolant tank) seems to be staying electrically charged when the car is shut off. I can no longer attach the red Ctek alligator clamp to the positive terminal without loud pops and sparks flying. It’s actually pretty scary. The car is off, key removed and alligator clamps are not even plugged into the Ctek. Has anyone experienced this? I’ll take some good theories, too! Thanks, Doug
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08-17-2023, 05:19 AM	#2
amrazM mTekMods 2143 Rep 2,902 Posts Drives: like a granny. Join Date: Jan 2010 Location: Manhatan iTrader: (1)	where is the negative connected? __________________ 2011 Frozen Black/Fox Red E90 M3 650+WHP G-Power Supercharged First DCT to Manual Conversion Worldwide KW CS, BBS RI-A, BW Headers, Snow 2.5
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08-17-2023, 05:33 AM	#3
aisthetes First Lieutenant 13 Rep 340 Posts Drives: 2013 M3 Competition Join Date: Sep 2008 Location: Colorado iTrader: (0)	To the factory negative post in the engine bay. I can’t even get that far. The positive pops and sparks first without the alligator clamp plugged into power.
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08-17-2023, 06:17 AM	#4
charliev68 Second Lieutenant 204 Rep 204 Posts Drives: bmw m3 Join Date: Feb 2020 Location: CA iTrader: (1)	Get a Meter and probe that terminal! See what voltage it is putting out.
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08-17-2023, 07:54 AM	#5
aisthetes First Lieutenant 13 Rep 340 Posts Drives: 2013 M3 Competition Join Date: Sep 2008 Location: Colorado iTrader: (0)	So I had an inexpensive electrical tester shipped last night. The positive terminal had low voltage going through. One bar on the meter with a slow beeping sound. An electrical wall outlet has two bars and faster beeps. I checked it again this morning. By now the car hasn’t been driven for three days. No beeping at all. I bought new Ctek alligator clamps to rule that out. No sparks at all and the tender is plugged in working fine again. So it seems like suddenly the positive terminal is holding a charge for a period after the car is off. The last two years I could charge it right away never with a spark or issue. Could this be a random power surge? Maybe issues with the battery slowly failing?
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