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Old 04-08-2011, 02:52 PM   #1
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Alternator Questions

according to SGII, the alternator in my 97 civic lx is...well alternating...from 12 to 14 volts while the car is being driven. load is not a factor--it seems to be intermittent.

i've replaced a few alternators in my day, but none that are this difficult to get to. GM alternators(what i'm used to) are generally right on top of the motor, but this one is mounted such that steering and/or suspensions parts have to be moved for access.

anyway, i'm debating(if this alternator is on its way out) whether to get an OEM Denso(expensive and 1 year warranty) or a store brand(less expensive and lifetime warranty). in the past, i would go cheap considering it wouldn't take much effort to reinstall another.

i will likely require help if this project needs to be done(still need to check the electrical connections and belt), and i do NOT want to do it more than once!

thoughts?

edit: FYI...battery is new
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Old 04-08-2011, 03:59 PM   #2
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Re: Alternator Questions

Take a second look at the alternator. I remember helping my uncle on his old Accord. We thought the alternator was going to be hard, until I suggested taking a wheel off, and doing the alternator through the fenderwell.
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Old 04-08-2011, 11:19 PM   #3
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Re: Alternator Questions

Two things-
Check all grounds first. Worth a shot. Find one bad one in a place where it counts and it could show an intermittent voltage issue.
I don't think honda is this way, but I know my Volvo uses a separate (replaceable) voltage regulator installed in the alternator. It houses brushes that touch the rotor of the alternator and those wear out. Verify that you can't simply replace the voltage regulator before buying a new alternator.

Cheap brand or Denso depends on how long you plan to keep the car. I'm a big fan of the cheapest parts for most applications. An alternator is pretty simple... it only fails in a couple of ways. Bearing failure, voltage regulator/brushes failure, maybe something else. Someone put a cheapo brand alternator in mine before i bought it. It's lasted me 15k with no issues. Sure it's a pain to replace (maybe not with Jay2theresuce's suggestion, which I second) but they typically last many miles. That said, if you plan to keep it for 100k or more consider the expensive one.
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Old 04-09-2011, 06:48 PM   #4
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Re: Alternator Questions

I wanted OEM for my Civic and found a remanufactured Denso on the Denso website for a few bucks more than the reman 'not Denso' brand at the local auto store.
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Old 04-10-2011, 11:04 AM   #5
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Re: Alternator Questions

thank you! good info. the denso site was MUCH cheaper than the local part store prices as well!
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Old 04-12-2011, 09:16 AM   #6
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Re: Alternator Questions

Is this a recent development?
What I gathered from an HHR site, is that alternator will put out 14+ volts only when in charge mode. Presumably when the computer decides the battery needs to be charged.

I know you stated the battery is new, but how long did it sit on a store shelf? Perhaps it didn't have a full charge going into the car.
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Old 04-12-2011, 01:26 PM   #7
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Re: Alternator Questions

the battery sticker says 10/10, so i would presume that's a manufacture date? i would consider your HHR site advisement, since i've had no starting issues. maybe actually seeing what the alternator is doing(via digital SGII) is unnerving me for no reason, if it's "supposed" to do that.
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Old 04-12-2011, 02:04 PM   #8
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Re: Alternator Questions

Quote:
Originally Posted by trollbait View Post
Is this a recent development?
What I gathered from an HHR site, is that alternator will put out 14+ volts only when in charge mode. Presumably when the computer decides the battery needs to be charged.

I know you stated the battery is new, but how long did it sit on a store shelf? Perhaps it didn't have a full charge going into the car.
i dunno what the goofy european and or jap stuff does but i know gm ford Chrysler its 14 when running and 12 when not all the time.

its just a big ol wire from the alternator, thru a fuseable link to the pos post.

if its fluctuating id suspect a bad voltage regulator, it goes to 14 when its working right then when it craps out runs off battery voltage.

id just take it off and haul it to autozone / advance for free testing. then it will be a clear cut and dry case if its bad or not.
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Old 04-13-2011, 11:04 AM   #9
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Re: Alternator Questions

Do you actually have a problem? Or just symptoms? Unless you are killing batteries or being left stranded, things might be fine...

Does SG actually measure voltage or get a voltage output from the computer? In either case, it might not be an issue. I've seen some ECM voltage readings that were annoyingly inaccurate (especially on GM cars).

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Old 04-13-2011, 11:11 AM   #10
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Re: Alternator Questions

13.8 tends to be the norm. After a start up it jumps to 14.4, but not always. The scangauge once reported 12.8 for a couple of days over the winter.

At least in the case of AGM batteries, a flat 14 volt continuous current will shorten the battery's life.

I've read a sitting lead acid battery needs a maintenance charge about every six months to replenish loss from self discharge. If a charger is readily available, I'd try topping off the battery first. At most, you'll have to disconnect the battery. So start with the least effort fixes first.

But I suspect it's nothing. The SG is giving you real time reports from the car's computer. Taking voltage multiple voltage readings, while the car is in motion, is likely something you haven't done before. I'd start worrying when the voltage is regularly going under 12 while the engine is running.

Currently, I just check the volt reading to see if it's below 14 before EOC/FAS. Presumably, this means the battery is fully charged for the restart. And I watch it while the engine is off to not let it drop below 11.6 before restarting.
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