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Old alternator checked at 15 volts, but would not charge ...


Sent to Car Experts June 23, 2006 3:13 p.m.

Old alternator checked at 15 volts, but would not charge on car, bought new alternator and batttery and STILL will not charge on car.

Optional Information:
1990 Nissan Maxima V6 3.0L

Already Tried:
New Alternator and new battery
Customer (name blocked for privacy)
Status: Closed   Value: $15   
Answer
June 23, 2006 3:30 p.m. (17 minutes and 25 seconds later)
ACCEPTED Check Mark

Hello!

If the original alternator was putting out 15 volts, you did not need to replace it; that is normal charging voltage. There is a remote possibility that the new one may be faulty; you might want to have it tested or re-install the known good old one if you cannot get things to work. We have found through years of experience that alternators from discount stores such as Autozone or Advanced often do not work right out of the box; they buy their parts from the absolurtecheapest sources they can find, and the quality is very poor. You won't find very many professionals buying parts from discount stores for this reason.

Assuming the alternator is OK, the problem may be in the vehicle's wiring. I have posted for you below the electrical diagram of your vehicle's charging system from the service manual, to help you locate the problem.

You should have battery voltage at the alternator output wire, and voltage should be present on the other hot wire at the alternator when the key is turned to the "run" position. If either of these wires has no power when checked with a test light or DVOM, there is a problem in the vehicle somewhere.

You will note that these circuits are protected with fusible links; one near the battery and one in the fuse box. If one of these wires has no power, check the appropriate link to see if it is blown.

I hope this is helpful; if so, please click my accept button! thanks!

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PictureSteve7654  -- Auto Service Technician -- 100% Positive Feedback on 1541 Car Accepts
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