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#3228253 - 12/26/13 12:27 PM Alternator? Bad ground? Something else?
DemoFly Offline


Registered: 06/03/12
Posts: 971
Loc: Bremerton, WA
Car: 2003 Mazda 6 2.3L

Symptoms: Power surges low every 20 seconds or so. Headlights dim, blower motor slows down. The rest of the dash lights and such seem fine.

Battery is at tip-top charge after running. Battery is also only a couple months old.

It literally seems as if something is drawing 200+ amps every 20 seconds.
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#3228262 - 12/26/13 12:30 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
Rand Offline


Registered: 08/20/03
Posts: 11906
Loc: NE,Ohio
Is that at idle or any speed?

how many miles?

possibly worn out alternator.

if it does it that regularly.
put a meter on the battery and see what the volts are
when its doing this problem.

If its dropping down to battery voltage you probably have an alternator issue.

alternatively you can pull it and have it tested.


Edited by Rand (12/26/13 12:30 PM)
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#3228263 - 12/26/13 12:30 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
Quest Offline


Registered: 12/19/04
Posts: 7362
Loc: beaver land EH?
get some voltage readings for us first before we can start our discussion on the subject.

Q.
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#3228283 - 12/26/13 12:45 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
Donald Offline


Registered: 03/21/04
Posts: 19213
Loc: Upstate NY
Most alternators are grounded via the alternator housing. So it may not hurt to loosen things and wire brush that area.

So a 10 year old alternator with over 100K probably. Is this the one that came with the vehicle?

Have it tested at a rebuild shop, it may be something cheap like new brushes.

Having your alternator rebuilt at a rebuilt shop is better than getting a rebuilt from AZ/AAP that was done overseas.
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2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)


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#3228297 - 12/26/13 01:00 PM Re: Alternator? Bad ground? Something else? [Re: Donald]
DemoFly Offline


Registered: 06/03/12
Posts: 971
Loc: Bremerton, WA
Originally Posted By: Donald
Most alternators are grounded via the alternator housing. So it may not hurt to loosen things and wire brush that area.

So a 10 year old alternator with over 100K probably. Is this the one that came with the vehicle?

Have it tested at a rebuild shop, it may be something cheap like new brushes.

Having your alternator rebuilt at a rebuilt shop is better than getting a rebuilt from AZ/AAP that was done overseas.

Original alternator.

Voltage @ batt terminal starts at 14.1v and slowly climbs to 15.5v then drops to 12.4v then jumps to 14.1v and slowly climbs back up to 15.5v and then repeats the cycle.
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#3228301 - 12/26/13 01:03 PM Re: Alternator? Bad ground? Something else? [Re: Donald]
AndyinAL Offline


Registered: 03/14/10
Posts: 79
Loc: Somewhere on the flat earth
AC compressor cycling (loss of power) coupled with the engine and condenser fans kicking on at the exact same time (momentary voltage drop due to electrical load of fans)???

Just a thought. Seems as cars and systems age, engagement is not nearly as seamless as when new.

Maybe the system is overcharged / restricted by chance. Could explain the increased load when compressor engages, then shortly shuts off because of hi pressure safety switch. Seems like with modern vehicles and automatic climate controls there are very few settings that keep the compressor turned off. Notice when sitting at a stoplight, regardless of temperature, AC compressors of surrounding cars are cycling on and off for no apparent reason.


Edited by AndyinAL (12/26/13 01:10 PM)

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#3228307 - 12/26/13 01:12 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
SrDriver Offline


Registered: 12/09/06
Posts: 2775
Loc: Southeast Alabama
Remove and take to local rebuild shop. They can test and rebuild it and if done right is better than a replacement.

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#3228314 - 12/26/13 01:21 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
Donald Offline


Registered: 03/21/04
Posts: 19213
Loc: Upstate NY
Originally Posted By: DemoFly
Originally Posted By: Donald
Most alternators are grounded via the alternator housing. So it may not hurt to loosen things and wire brush that area.

So a 10 year old alternator with over 100K probably. Is this the one that came with the vehicle?

Have it tested at a rebuild shop, it may be something cheap like new brushes.

Having your alternator rebuilt at a rebuilt shop is better than getting a rebuilt from AZ/AAP that was done overseas.

Original alternator.

Voltage @ batt terminal starts at 14.1v and slowly climbs to 15.5v then drops to 12.4v then jumps to 14.1v and slowly climbs back up to 15.5v and then repeats the cycle.



Over 15v is too high if you are measuring it at the battery with a quality meter.

Remove and bring to a rebuild shop.
_________________________
2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)


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#3228315 - 12/26/13 01:22 PM Re: Alternator? Bad ground? Something else? [Re: SrDriver]
Donald Offline


Registered: 03/21/04
Posts: 19213
Loc: Upstate NY
Originally Posted By: SrDriver
Remove and take to local rebuild shop. They can test and rebuild it and if done right is better than a replacement.


Unless your original is a Mando (Korean) alternator and if so get a Delco to replace it.
_________________________
2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)


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#3228339 - 12/26/13 02:02 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
TFB1 Offline


Registered: 09/03/10
Posts: 3496
Loc: VA
Originally Posted By: DemoFly

Voltage @ batt terminal starts at 14.1v and slowly climbs to 15.5v then drops to 12.4v then jumps to 14.1v and slowly climbs back up to 15.5v and then repeats the cycle.



Sounds like it's over charging then "catches it'self" and cuts out completely so you just have battery voltage... Assuming the connections are OK you could replace the regulator but most are internal these days(a few are mounted externally on the alt) requiring dissambly of the alt...

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#3228411 - 12/26/13 03:22 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
Quest Offline


Registered: 12/19/04
Posts: 7362
Loc: beaver land EH?
Make sure that your A/C compressor is not cycling, and your engine has reached normal operating temp.

Measure your voltage reading again: should be within 13.5V ~14.5V DC without fluctuations.

If it fluctuates, and assuming that there are no other parasitic loads elsewhere (such as rear window defroster, A/C compressor cycling, etc.), then suspect that your alternator is at fault.If it's a Nippon Denso varieties, get a remain from Denso(ditto for Mitsu).

Q.
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#3228485 - 12/26/13 04:55 PM Re: Alternator? Bad ground? Something else? [Re: DemoFly]
Dufus2 Offline


Registered: 12/12/13
Posts: 259
Loc: Virginia
I had a similar experience with the supply wire to the battery and possibly a fusible link. Check your wiring before condemning the alternator. Also, there may be issues with the F terminal going back to the ignition, cycling the alternator just like the A/C works.
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#3228948 - 12/27/13 07:25 AM Re: Alternator? Bad ground? Something else? [Re: Dufus2]
JetStar Offline


Registered: 10/02/08
Posts: 1499
Loc: Flatlands of Indiana
Is your alternator output controlled by the computer?
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