Parastic drain from 10A. ALT.S fuse. What is it?

[germantown]

My maxima GXE 2000 died twice after weekends. Battery drained completely. Car can start after jump start with a portable charger.

When measuring 10A current, I got Now the correct reading is 0.55A drain. After several tries, I got 10A. ALT.S fuse for drain of 0.5A (Before removing it, I got 0.55A. After removing it, I got 0.045A). Clearly this is the problem.

Here are my questions:1. Is this fuse related to Alternator? I just replaced the Alternator 2 months ago. Does that mean something wrong with the Alternator?

I suspect some diodes inside Alternator have shorting issue, which causes the drain. However, the alternator works fine which output voltage is around 14.10V when tested while idling. When tested while key off, the battery reads 12.4V.

2. will a shorting diode inside Alternator drain the battery even when car is off? Will a shorting diode fail the whole alternator?

3. The fuse itself looks OK. Should I replace it?4. How can I dig further to find the exact problem for this drain?

Thanks,

[hwyix]

There is no way your car should ever have 10amp drain. Anything below 50 miliamp drain is good.

A bad alt will cause your car to drain its battery even if it charges it correctly.If your measured drain goes away when you disconnected your alt, youralt is bad.

[Ladreik]

Just FYI another easy way to check the ALT for shorted diodes is to check AC voltage. If you have a significant amount of AC voltage your Diodes are shorted.

[morsecode]

Must be a bad alternator if you don't retain the charge. It needs to be replaced.

[fixer]

disconnect the plug on the back of the alt. if drain goes away, replace alternaotor

[germantown]

There is no way your car should ever have 10amp drain. Anything below 50 miliamp drain is good.

A bad alt will cause your car to drain its battery even if it charges it correctly.If your measured drain goes away when you disconnected your alt, youralt is bad.

Sorry for that I didn't say it clearly. It's the fuse name, 10A ALT.S, not 10a drain. I got 0.550 A drain. I thought it might be ALT or some cable connected to ALT is loose.

How to disconnect the alt? Which cable should I disconnect? Where is it? Is a good way to test the cable from ALT?

Thanks,

[germantown]

Just FYI another easy way to check the ALT for shorted diodes is to check AC voltage. If you have a significant amount of AC voltage your Diodes are shorted.

I measured the voltage for ALT. It's 14.0 or 14.1V when tested idling. What's the exact range if Diodes are shorted?

Thanks,

[germantown]

disconnect the plug on the back of the alt. if drain goes away, replace alternaotor

Where is the plug on the back of the ALT? Can I access it from the top? Do I have to access it beneath the car?

I found a pic from cardomain (http://www.cardomain.com/ride/748507/23). Is the number 5 is the plug you talk about?

[germantown]

Must be a bad alternator if you don't retain the charge. It needs to be replaced.

It might be possible. However, I have my ALT replaced 2 months ago. Voltage charged without any drain if I unplug ALT.S fuse. Is it possible that the ALT harness or ground cable has problems?

[hwyix]

It might be possible. However, I have my ALT replaced 2 months ago. Voltage charged without any drain if I unplug ALT.S fuse. Is it possible that the ALT harness or ground cable has problems?

I don't know everything that is connected to your ALT.S fuse. I would ASSume it is just your alt. Like I said earlier just disconnect your alt at the alt. There should only be two wires there. If the drain goes away it is your alt. If the draindoes not go away there is something else on the ALT.S fuse other than justyour alt. Look at a wiring diagram for your car. Someone might have spliced into the wire for an alarm, etc... who knows what.

[ShaunakaRichard]

Am I the only one finding it hard to believe that the alternator fuse is 10A? ALT.S could very well be something else. If I were you I'd do some looking. 10A is extremely small. The rule of thumb is whatever the expected draw is double that for the size of the fuse. To be 10A it means its designed to normally have 5A or less going through it. An alternator puts out significantly more. No way thats the main fuse to the alternator.