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Second Alternator took a dump. Looking for electrical guru troubleshooting advice.

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Second Alternator took a dump. Looking for electrical guru troubleshooting advice.

 
Old 10-06-2017, 03:42 PM
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Second Alternator took a dump. Looking for electrical guru troubleshooting advice.

Hey guys,

My OEM alternator went out about 2 months ago. Voltage randomly dropped one time to about 12V and gave me the warning but came back up after a few seconds, then it didn't happen again for a few days. The it happened again a couple more times randomly, then I saw a spike to about 16V, it dropped to battery voltage and didn't pick back up again. I tried the regulator first, but it ended up being the alternator.

I've had my new one in for about 3 weeks and two days ago I got the stupid voltage drop randomly again to battery voltage. It picked right back up to normal, and ran out basically the same course as the first alternator dropping a few times then coming back, then a spike to 16.5V and toast.

When the alt was working I measured 12.5V front battery, 11.9V rear battery, and both of them picked up to >14V with the car on. I'm guessing there is maybe a faulty component some where over loading the alternator maybe, I was just wondering if any one has seen something similar to this or if has any ideas of the culprit? I don't have the total current draw on the alternator while running but I'll grab it next time I have a working alternator in. Just looking for any trouble shooting ideas.

Thanks guys.
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Old 10-06-2017, 04:28 PM
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PM me your email address and I'll email you some tech info on the dual-battery system if you don't have it already. For now, I'd hook up the diagnostic system and query the Battery Control Module for faults. I lean towards a bad alternator but the exact same failure symptoms sure make one suspicious...

Edit: just re-read your post. 11.9 volts on the rear battery is way too low. Pull the ground cable; if it still reads 11.9, I'd suspect a bad battery. This is why I recommend the Solar BA-5 or 7 battery test device; it allows me to track the health of the battery and replace it when the cranking amps get too low.

Last edited by bbirdwell; 10-06-2017 at 04:30 PM.
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Old 10-06-2017, 04:34 PM
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Originally Posted by bbirdwell View Post
PM me your email address and I'll email you some tech info on the dual-battery system if you don't have it already. For now, I'd hook up the diagnostic system and query the Battery Control Module for faults. I lean towards a bad alternator but the exact same failure symptoms sure make one suspicious...

Edit: just re-read your post. 11.9 volts on the rear battery is way too low. Pull the ground cable; if it still reads 11.9, I'd suspect a bad battery. This is why I recommend the Solar BA-5 or 7 battery test device; it allows me to track the health of the battery and replace it when the cranking amps get too low.
Awesome thanks for the info, I found several threads where people were suggesting that upper 11s were okay on these batteries. I'll get that turd swapped out along with the alternator then.
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Old 10-06-2017, 06:56 PM
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How old is your main battery? 11.9 is well below the 12.3V minimum that a battery should show at rest. Get a load test on that battery; I'll bet you'll find it is the reason your alternators are being killed.
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