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Randall C
Randall C, ASE Certified Technician
Category: Car
Satisfied Customers: 12728
Experience:  32 years Foreign / Domestic Cars All aspects of Diag and Repair
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Suzukiq XL7: Working on a 2002 XL7, alternator tested good

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Working on a 2002 XL7, alternator tested good at parts store (made them run it 4 times) and at plug at back of alternator I have battery voltage on both pins of the plug with ignition on, but alternator is not charging... Battery voltage at main post on alternator...
Hello, I am Randall.
When you trun keyb on only, not runnning, does the charge light come on the dash?
Customer: replied 3 years ago.

yes it does but as soon as the car starts the charging light goes out

ok, so what voltage do you get at the battery terminals with engine running? also with engine off
Customer: replied 3 years ago.

Key on engine off is battery voltage (12) Engine running is 7 volts

Odd, as the volts drop so much running. Th battery is 100% strong? no jumping needed? you can turn lights on etc when running and it still runs ok for a bit?
Customer: replied 3 years ago.

it does start on its own. I haven't times how long it will run but the lights come on automaticallyand it does stay running a bit

The only thing I can answer with? I am not a big fan of bench testing alternators. I have found that not to be 100% concluisve
All you need is the light working, power to the big white wire, and power to the one small wire at plug, the Black/white wire
the other wire is not tested as it really only provides ground for the light to be controlled
You say you have everything needed and it is not charging
I doubt some kind of short
the battery does have to be at least 70% charged in order for the alternator to kick in.
Since you have everything that is normally tested and still no charging? the only things I can say is a porr connection at the alternator plug OR what I lean more to? you do in fact have a bad alternator irregardless if they say it has passed several times
I would charge battery for good while. The try one more time but doubt that is it. Just have to mention in case alternator is sensing just a littl too low battery voltage.
If problem persists? your voltages remain and plug connection is good? then I have to say failed alternator
It really can not be anything else
The diagram is below. It is a simple charge diagram rather than a computer controlled system like most newwer vehicles
I realize you have your doubts about alternator as being bad but,, I am not there, I am going by your tests and voltages and really feel the alternator is in fact failed

Customer: replied 3 years ago.

Ok, i will charge the battery and have it tested. Is there a reason that the charge light wouldnt illuminate when it was not charging though? Once the car is running the light goes out completely even though the battery isnt being charged...

It is possible. The regulator controls the light. I have run into many that the light does not come on when not charging. depends on what internal circuit failed
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