Parasticcc drainnnn

Guys is that normal for alternator to draw when the car is turn off?the draw just gone when i remove the alternator batt wire…any idea about what problem is that…the car battery will drain overnighy

A bad diode in the alternator will cause a current draw off the battery.



It is possible, yes. Not a common thing unless jump starting damages diodes
. If so alternator is replaced.

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i can comfirm that the alternator is in good condition cause i already open it and take it to expert and tested it

The alternator is brand new and tested by mechanic

Just because the alternator is charging properly, doesn’t mean you don’t have a faulty diode.
Your symptoms indicate your new or rebuilt alternator has a faulty diode.

from the link @Tester provided

Bad Diode

A malfunctioning diode in the alternator can create a parasitic drain on a car’s battery. Diodes should allow current to pass in only one direction, but a bad diode will keep the charging circuit open even when the engine in not running, allowing the battery to go dead. This often happens overnight.

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yea thank you for that good information…i know a bad diode will causing parastic drain so i already take it to dealer and tested it and also i test it with multimeter and higher number in one side and zero on other side…

One possible choice is that the cable to the alternator is grounding somewhere.
Otherwise, I would still be suspicious of a bad alternator and would take it to Adv Auto for a free test.
I am surprised you diagnosed this is alternator current with the car off. Can you bypass the cable with jumper cable, and then check for a current?

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when i connect the black lead to battery negative post and red lead to terminal and the result make me confuse.someone explain it?is that 0.28 miliamp right.

when i turn the multimeter from 10 to 20m and the result is 0.20MA…

This is 280 mA. About right for when you first make connection and modules are awake. After some time of inactivity, the modules will go to sleep and draw less power. That time varies by manufacturer.

But I think I see a problem. You have selected 10A scale but your red probe is in the mA connector. To work as 10A it needs to be moved to the 10A max jack on the far left…


You want the meter set to the 20 volt DC scale.



that make sense i already let the car sit for one day before i do the test all the door close by taping it and the alarm and clock everything i been remove it

sorry for my bad english what that mean…meter set to 20volt dc for what?

when i move to 10A scale its show nothing…


I got you confused with the Honda charging problem.


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I like to watch the current change and see both draw rates. You have to be careful, the mA input is fused lower. You could blow the fuse and it will no longer register any current on the display. Here’s what I do-

I made a shunt out of a short length of heavy gage wire. Maybe 8 to 10 gage. I disconnect negative battery cable. I connect the shunt wire between cable and battery post. Then connect my ammeter leads to cable and post. By then, the huge in rush current has dissipated and i can remove the shunt. Now my meter is reading the <1A current draw without blowing the meter fuse. Watch the meter every so often over 15 to 30 minutes. The current will drop as modules go to sleep.

Check your meter fuses to be sure they are ok. You could have blown them in your testing. Also be sure to plug the meter lead into appropriate jack for the scale selected.

If you see typical draw when sleeping, the problem may be that they keep waking up for some reason; intermittant door switch for example. It may take time to find it

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Got it bro that new knowledge for me i will try to do it and i will make sure my multimeter didn‘t blow fuse…i will try my best to find the draw lol if i cant still find it i will make a battery kill swich …

Im planning to make a battery kill switch in the beginning but the kill switch look so ugly lol…

I try using old method using the test pen between the battery post and the terminal and the light just bright up and the light gone when i open the alternator socket…