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Is my charging system normal?


Topic starter

hi scotty and everyone! After watching your videos daily for sometime now, I recently purchased topdon battery tester, and both my battery and starter passed the test. however, my charging systems seems to fail. I then used my multimeter to confirm the problem, at idle (no load) the multimeter only reads out 12.47v -12.56v however, when i turn on the lights, ac, and radio it will constantly read 13.9v-14.5v. I dont mind changing the alternator myself but i need to be sure that there is a problem. I badly need your advice. oh btw, my car is a 2012 honda civic 1.8 auto with 85,000km. Thanks for your help, all the best form Edmonton AB CA. 

This topic was modified 3 weeks ago by
5 Answers

I would replace it. At idle with no accessories running you should see 14V or so. Showing less than 13V at idle tells me you have an issue.

This used to be always true, but now the charging voltage is continuously second-guessed by the system computer's software. If the voltage is good when you first start it, and steps up as well when the headlights are on, a lower voltage at other times is likely intentional.


Well as long as the wires are tight and the belt is tight and there's no corrosion in any of the terminals replace the alternator

Topic starter

nope, belts is new 2 months ago, terminals are cleaned and I've checked the wires previously. thank you scotty! will do that before winter, keep up the great work man! thanks


I don't see an actual problem.  This behavior is due to computer software juicing the mpg. There is nothing wrong with an alternator that puts out 14+ volts regulated with the lights on, but less with them off. (see my post of yesterday:   The tester just has no way to accommodate or acknowledge the computer system control over charging voltage.


The tester is correct. Your alternator is bad.

12.47v -12.56v is too low. That means your battery is discharging.