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Discussion Starter #1
Hello all!
Odd situation here. 05 with 118k. Had the alternator replaced a few months ago, and since then whenever I get the RPM's above 5000 the battery light flickers until the trans shifts and the RPM's drop. I'm thinking any time the battery light is involved, it is alternator based but I'm not sure.
I haven't seen the battery light on or flicker any other time, but now I am paying more attention as I drive.
Anyone have any insight into what might be going on here?
Thanks in advance!
 

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Typically high revs and a battery light (even flickering) that disappears once the revs drop is an overcharging condition - could be borderline overcharging given the flickering.

You can easily determine if thats whats occurring if you have an OBD test tool plugged in while driving. If thats not the case, I'd check the 4 pin connector on the alternator and for bad/corroded grounds - on thermostat housing, near battery and above radiator to start.
 

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Do the checks that Mark suggests.

FWIW, Generic "Rebuilt alternators" often get cheap regulators installed in them. In my experience as a mechanic, about half of these budget rebuild fail within 6 months.

If you have a digital multimeter, use a power socket adaptor and watch for voltage fluctuations. Or you can buy a plug in voltmeter. (LIKE THIS: https://www.amazon.com/INNOVA-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=sr_1_4?s=automotive&ie=UTF8&qid=1505273945&sr=1-4&keywords=plug+in+voltmeter)

A stock Acura gen. 1 alternator will put out a rock solid voltage between 14.0 and 14.4 volts.
 

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Bluepill is dead on. His post got me thinking that I'd like to have an easy battery monitor, just because. I found these, which would be cheap enough to drop one in each of my car's (and motorhome's) glovebox, just to plug in if there was ever a question about the condition of the battery / alternator...

https://www.amazon.com/dp/B00AQAQIGO/ref=sxbs_sxwds-stvp_3?pf_rd_m=ATVPDKIKX0DER&pf_rd_p=3171424582&pd_rd_wg=UKgxg&pf_rd_r=V5V8BFX62CQ5KZWMBD31&pf_rd_s=desktop-sx-bottom-slot&pf_rd_t=301&pd_rd_i=B00AQAQIGO&pd_rd_w=gDoJw&pf_rd_i=cigarette+lighter+voltmeter&pd_rd_r=GN5W077M9CZ17755V531&ie=UTF8&qid=1505327683&sr=3
 

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bluepill -

whats the average life expectancy of an OEM Acura MDX alternator? My MDX has 145K miles and I plan to take it on a 1500 round trip road trip...hate for that to fail with the family in the car.

thx
 

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bluepill -

whats the average life expectancy of an OEM Acura MDX alternator? My MDX has 145K miles and I plan to take it on a 1500 round trip road trip...hate for that to fail with the family in the car.

thx
The factory supplied alternators for Gen 1 MDX are "Denso" brand. They usually last for 140K to 175K miles unless abused by reverse polarity connection. What usually fails are the brushes inside the unit. We used to just replace the brush set and test the regulator and they would go well past another 100K.

The bad news is that generic rebuilders just take apart failed units and replace only those parts that have actually failed, as opposed to Acura Genuine Remanufactured units that get full testing, all new bearings, brush sets, and regulators. If it was my car, I would bite the bullet and get an Acura unit. You can get them for about $260 from internet dealers. Do this only after testing all wiring and connections first, as mentioned above.
 

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As an anecdotal data point, my alternator died at 215,000 miles (no symptoms prior to failing to charge).

Unfortunately, it happened in the middle of a long road trip, pretty much in the middle of nowhere (in west Texas on I-10). But the fix was simple enough - as long as you have a 14mm socket and beefy enough extension to crank the serpentine belt tensioner to reinstall the belt. The main bolt could be a little sticky (also a 14mm). The area is cramped - but you can get the alternator out and the new one back in without taking anything else off. I pulled the old one out in the rest area waiting for the tow truck, and put the new one in in 15 minutes at the hotel across the street from the Autozone (where the tow truck dropped us off). Really not to traumatic at all - if you're worried about the alternator and plan on keeping the car for a while, just travel with a good rebuilt alternator. Worst case, you can sell it if you end up selling your MDX before you need it.
 

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Discussion Starter #8
Update - I took Bluepill's advice and bought the digital multimeter. I attached it and it is showing half a battery left, and the reading fluctuates between 12.5 and 13.9 most of the time that I glance at it (which isn't too often because it's dangerous to watch it while I'm driving!). When I "floor it" and get the RPM's up so that the light flickers, I see that it is showing between 13.5 to 14.2 pretty consistently.
I'm thinking that is good? I'm just wondering why that light flickers at all though.
 

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Re alternator life and having a spare, here's an option but probably not for everyone. The unit on my 06 X died around 120K miles with electrical howling like a bad rectifier. I found a used Denso with 60K on car-part.com for $60 at a local yard. I have an 08 TL with 167K and same alternator so with the experience on the X, I found another unit on car-part with 80K for the same price also at a local yard. I installed that one to make sure it works and the original is now a spare.
 

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Update - I took Bluepill's advice and bought the digital multimeter. I attached it and it is showing half a battery left, and the reading fluctuates between 12.5 and 13.9 most of the time that I glance at it (which isn't too often because it's dangerous to watch it while I'm driving!). When I "floor it" and get the RPM's up so that the light flickers, I see that it is showing between 13.5 to 14.2 pretty consistently.
I'm thinking that is good? I'm just wondering why that light flickers at all though.
Sounds more like to me that the alternator is bad.

It should be 14.0 while the car is running and shooting to 14.5 when reving I believe.
 

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Discussion Starter #12
Update 2 - REALLY paid attention today on a one hour drive on the turnpike...and it was pretty steady at 14000 and it pretty much stayed there even when the light flickered.
Had the shop that put the alternator in check and they said it was showing what it should too.
Lovely...I just wish I knew why that thing flickers. I know the old joke, "hey doc, it hurts when i do this" and the doc says "then don't do that" but that's not cutting it for me!! :)
 

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There's not a whole lot to the circuit - it's pretty much got to be the voltage regulator inside the alternator, or wiring / fuses. Here's a diagram and the troubleshooting instructions...


 
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