Alternator?

 
rberq
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Post by rberq » Mon. Apr. 24, 2023 4:10 pm

I decided to post here rather than on a car forum where most people know lots of stuff that isn't true. :roll:

I have a 2016 Honda Accord. 73K miles. No apparent problems except the battery is getting a little old. The mechanic told me the alternator puts out a maximum 51 amps and should be replaced to the tune of $700 to $800. I hooked up my voltage meter to the battery, engine off, and it was 12.5 volts. Then I started the engine, the meter showed 12.6 volts at idle. Then I turned on everything electric that I could find, still at idle, the meter STILL showed 12.6 volts. When the AC compressor kicked on, voltage would briefly drop to 12.5, then engine RPM would increase a bit and the meter would go back up to 12.6. Been driving trouble-free for weeks now since I was recommended to replace the alternator.

My conclusion is that the alternator is putting out as much juice as needed, even at idle, and there is no reason to replace it. 51 amps may be below spec but still is plenty adequate. Am I missing something?


 
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Post by waytomany?s » Mon. Apr. 24, 2023 4:32 pm

You mean other than an $800 bill? It does seem low. My Cruze shows 12.4 on cars gauge with key on. 14.5 when running down the road. See if you can find better price on line and install yourself.

 
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Post by warminmn » Mon. Apr. 24, 2023 4:42 pm

I drive older stuff but I dont worry about any of that crap until it doesnt start. If the battery is real old I might replace that. Headlights on, AC on, wipers on, if that doesnt drain it I doubt its a problem, at least to me.

 
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Post by mozz » Mon. Apr. 24, 2023 5:14 pm

Pull the battery and put it on a charger, when fully charged and cooled down, then measure the voltage. If it's not dropping in the car i guess the alternator is doing it's job. You can also switch the meter to AC and see how much ripple it has, compare it to another car, if excess ripple, i would say a shorted diode.

Batteries every 5 years on my cars. Whether they need it or not. Heat is what kills batteries, not cold. Never had to replace a alternator. Before the 15 year mark, car is usually sold and on to the next vehicle.

 
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Post by Rob R. » Mon. Apr. 24, 2023 6:13 pm

A fully charged battery should measure 12.6 volts, and with the car running you should see at least 13.8 volts.

If the battery is old I would replace it. Bring the alternator to a local shop and have it checked.

 
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Post by Richard S. » Mon. Apr. 24, 2023 6:16 pm

AFAIK that is low, with the car running the ones I have tested usually read 14.X volts. My car has a display for voltage on the dash though menu option. When I took my trip in September I was checking it every couple of days and it was hovering around 14.5 to 14.8, once it was over 15.

The cost to replace it seems very excessive, is it buried? That's a 15 minute job on my car and around $100 for the alternator.

 
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Post by rberq » Mon. Apr. 24, 2023 6:44 pm

Richard S. wrote:
Mon. Apr. 24, 2023 6:16 pm
AFAIK that is low, with the car running the ones I have tested usually read 14.X volts.

The cost to replace it seems very excessive, is it buried? That's 15 minute job on my car and around $100 for the alternator.
The replacement cost estimate was mostly the price of a new alternator from Honda -- $$$ -- the shop said they have had too many failures with rebuilt and aftermarket units and only install the OEM ones now. They are tired of providing free labor for replacing the replacements, I suppose.

The charging voltages I am familiar with are around 14 volts, as you say. So a steady 12.6 is kind of a puzzle, but there is a new-fangled battery monitor attached to the negative terminal. If it detects the battery as fully-charged, why feed it 14 volts? I'm thinking that is just more sophistication in modern electronics, and is OK.


 
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Post by rberq » Mon. Apr. 24, 2023 6:49 pm

warminmn wrote:
Mon. Apr. 24, 2023 4:42 pm
If the battery is real old I might replace that.
That's my thinking, too. The shop said the battery is marginal, and it sometimes does get cold in Maine, so I will probably replace it before next winter.

 
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Post by Rob R. » Mon. Apr. 24, 2023 7:48 pm

rberq wrote:
Mon. Apr. 24, 2023 6:44 pm
The replacement cost estimate was mostly the price of a new alternator from Honda -- $$$ -- the shop said they have had too many failures with rebuilt and aftermarket units and only install the OEM ones now.
I don't blame them - most of the parts store rebuilt units are junk. I have had good luck with an alternator and starter from these guys: https://www.dbelectrical.com/shop/#/pf:ss_fitment ... D$253E2016

A good shop can also do a great job on a rebuild, but there don't seem to be many of them left in business. If you want to stick with OEM, a low mileage unit from a junk yard is an option also.

 
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Post by Richard S. » Mon. Apr. 24, 2023 7:55 pm

Just looked it up, cheapest one on Autozone is $384... ouch!

 
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Post by grumpy » Mon. Apr. 24, 2023 8:45 pm

Rockauto check it out

 
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Post by hank2 » Mon. Apr. 24, 2023 9:10 pm

A 12.6v charge will not charge a battery or come close to keeping up with running draw. High 13's minimum. As others said, charge the battery and see if it holds 12.6v overnight. A crapping out battery can take an alternator down with it.

I'm not familiar with Honda charging regulation. On GM trucks for many years, they use a constantly variable voltage control. If you put a voltmeter on it, it will.constantly jump around from 12.5 to 15.1. Only feeds in what's absolutely needed for a half second. Fuel mileage extremism.

The rebuilts are usually pure crap today, especially from chain stores. If a Bosch is available for your application, that might be ok. They at least change bearing, others only do brushes. They're all made up of piles of parts and may be way lower or higher output then you think you're buying. Maybe source used, if you replace the battery?

 
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Post by freetown fred » Mon. Apr. 24, 2023 9:17 pm

Bang the bottom on the floor a couple times--then put it on the charger--if it's a decent one. If it holds a charge overnight--like stated, you're good.

 
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Post by Retro_Origin » Mon. Apr. 24, 2023 9:26 pm

Am I wrong in saying a fast check is just disconnect the battery while the engine is running? If it dies then you know it was running off battery power. I've also heard and verified the fourteen volts. I put a non oem on my civic three years ago with no issues. Probably over forty thousand miles since. To me it seems like diagnosing batteries are the situations where the test might say good but the battery might not be, always thought alternators were easier to figure. If you're not opposed call a u pull it or junkyard. If you're allowed to walk around you will probably find an oem one. Could save you money. My two cents, honestly probably have the least experience of anyone on here with all that

 
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Post by hank2 » Mon. Apr. 24, 2023 9:40 pm

I have forgotten the reasoning, but the ancient pull off the battery cable running to test is said to be bad news on any semi modern vehicle.

Yeah, batteries can do some crazy things. AGM's especially. Heaven help you if you ever own a true gell (not AGM). I had one years ago and it nearly drove me out of my mind. Until I tossed it. Old school slosh battery can get a bad cell and mess with you. Then blow up one day.


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