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Charging system


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My charging system is having a problem;

Battery volts were low (10.5 or so measured on the DIC) and I took car to the parts store for quick diagnostic where they indicated the battery was good (less than a year old) but there was no alternator charging voltage;

I did some re-tests to check on the conditions after re-charging overnight:

Off-load battery was at 13.2V (measured ~ 0.5V less on the DIC);

after starting the car, the indicated voltage on the DIC dropped below 12V; it seems to handle load well enough (lights & A/C on); if I increase the engine RPM there is a delayed reaction on the voltage displayed on the DIC - it will increase gradually at a rate of 0.1V per second into the 13.7 range, then as I back off the throttle it will drop again. There are no error codes for insufficent charging etc or L-block issue.

So - obviously the alternator is making voltage but still points to a problem - maybe one of the diodes blown? Regulator issue?

Is it possible to replace just the voltage regulator? The alternator was replaced a few years ago and has maybe 50K miles tops? Should I just bite the bullet & replace the whole thing?

How does the battery/alternator tester they use differntiate between battery voltage & alternator charging voltage when they are hooked together - does it look for an AC component on the charging volts???

This thing as everyone knows is a PITA to get out or I would attempt to take it out & apart to get some further insight. The + cables at the battery don't look great so I will probably replace those along with any other repair that's necessary, but for now have cleaned them up reasonably well.

Opinions/confirmation on the diagnosis and repair?

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Is it possible to replace just the voltage regulator?

Yes, I am pretty sure you can take it apart and replace the regulator and rectifier bridge (diodes).

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Could be a short at the "L" terminal. I had the terminal short problem and it progressively became worse until the alternator completely gave out. If you notice that on starting the DIC displays BATTERY NO CHARGE then be aware that you may be experiencing the same problem; one minute everything will seem fine and, the next, you may see BATTERY NO CHARGE. Please keep us informed.

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There are no error messages indicating a charging problem; that's what confused me about the fact that the tester showed "no charging voltage", yet there is no associated error on the DIC; also it appears there is some kind of charging voltage although it is behaving strangely... I guess it could still be a regulator or connector issue.

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