2008 Acura MDX w/ 145k miles.

Had a 2 year old battery, so I replaced it under warranty and it started fine after that for about 2 weeks.

Wife tells me today that it's dead again. She says no dome lights left on, etc.

Could it be an alternator? Looking for ideas. Thanks!

alternator would be my guess or else some sort of parasitic current draw? did you recently install some new electronic device?

schmendeler said:

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alternator would be my guess or else some sort of parasitic current draw? did you recently install some new electronic device?

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Negative

Alternator is a good guess, maybe a bad connection. I don't think I had a car with good battery cables until I was in my mid 20's, I got to be pretty proficient at getting them to work again, poorly.

Check the connections. Maybe a half ass connection lasted 2 weeks before it worked itself loose. If not, alternator is probably next on the list. Most new cars will rev real high when the alternator is dying, trying to compensate for the lack of charge. Maybe she noticed this. Probably worth an ask.

get it started & put your multimeter on the alternator to see the voltage output.

Any brand/store y'all recommend for alternators?

Lifted from the net:
Denso is the OE manufacturer for Honda / Acura alternators and other parts, such as the AC compressor. Denso makes high quality parts. If you get the Acura replacement parts they come in an Acura box, but they are still Denso parts. This reman alternator gas been working well for me for a few months now. Quality replacement part for way less than you would pay at the Acura dealership.

Rock auto $110 before 5% discount (this price assumes you are sending them the core

Denso is a good pick.

Also Ultima from Oreilly has been a good brand for
Me.

Might as well do the belt at the same time too.

Had a similar situation on my truck I just replaced. Slow to crank. Replaced battery. Dead in the AM. Place I bought battery replaced with new battery. Carried on, but over time that first crank was worse and worse. Had to be something drawing power off that battery. A light or source somewhere.

With other issues as well, I figured it was time to spit the bit and get a new vehicle. Good luck. It's frustrating for sure.

If you jump start the car, does it stay running or die shortly after disconnecting the jumper cables? If it stays running for a while it's likely not the alternator. You can also just take it to a parts store and they'll test it for you.

It's also possible you have a bad component that is drawing current while the car is off. This is a bit more difficult to test for, but it's still something you can do on your own. Check for current draw through the negative battery terminal while the car is off. It should be just a few mA, less than 10. If it's in the hundreds you have something drawing power.

In addition to checking/swapping the alternator, also check your cables to make sure there's no loose connections or corrosion on the terminal clamps.

These are great little tools if your battery has a tendency to corrode during use (my Jeep is horrible about this)

A loose battery connection will cause starting problems.

Probably the alternator, but another issue might be that the ECM has stopped working correctly and isn't triggering the alternator to recharge the battery.

Had that happen to me once. Alternator tested bad, so bought a new one and installed it. Truck ran fine for a couple of hours, then died and wouldn't start. Went back and tested the new alternator and it tested bad as well. Swapped it out for another one. Same thing. At that point I took it to a mechanic. The mechanic found that the ECM was bad.

Thanks ya'll. I'll head down to the parts store shortly and have them test the alternator.

jakester03 said:

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2008 Acura MDX w/ 145k miles.

Had a 2 year old battery, so I replaced it under warranty and it started fine after that for about 2 weeks.

Wife tells me today that it's dead again. She says no dome lights left on, etc.

Could it be an alternator? Looking for ideas. Thanks!

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Years ago we had a 2008 Honda Odyssey where the battery would go dead. Battery was good/newish so didn't make sense. Jumped it once or twice and charged over night but came back. When in the garage for a while, doing something quietly, I realized I could hear a click sounds every once in a while - vehicle was off, hadn't been driven in hours, but a click kept being heard. Turned out it was an A/C relay gone bad and it was draining the battery. Since Honda's and Acura's may share many parts - could be impacting you as well.

Confirmed alternator. Thanks y'all!

WELP. Went out of town for the weekend and the damn thing is dead again! ARGH

jakester03 said:

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WELP. Went out of town for the weekend and the damn thing is dead again! ARGH

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Try unplugging the Hands Free Link unit https://www.mdxers.org/threads/battery-keeps-dying-2008-mdx-with-brand-new-battery.55801/

Someone in this thread recommends checking the A/C Relay, which is something i had mentioned in a post above. You should be able to hear some occasional clicking from the engine bay even with the vehicle off, but I recall having to wait a long time to hear it so it's a bit annoying to sit there waiting for a potential click sound.

Complete Idiot said:

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jakester03 said:

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WELP. Went out of town for the weekend and the damn thing is dead again! ARGH

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Try unplugging the Hands Free Link unit https://www.mdxers.org/threads/battery-keeps-dying-2008-mdx-with-brand-new-battery.55801/

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Done. Fingers crossed that works! Thank you!

https://acurazine.com/forums/3g-tl-problems-fixes-114/2008-parasitic-drain-already-disconnected-hfl-still-dying-within-day-886701/

Forgot to add the link in my last reply

JamesPShelley said:

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Have you considered just taking it to an auto parts store... Autozone... OReilly... whatever... and have them test it for you? For free...

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This. I replaced a battery and had it go bad a few weeks after. Had it tested and they replaced it under warranty.