So while waiting on the new alternator to arrive, I'm now trying to figure out what's draining the battery. The car dies won't go more than 2-3 days parked without being unable to start it without a jump.

I've been playing around with my multimeter and I'm getting about 300mA of current draw with the car off and doors closed. I tried waiting a bit to see if the car goes to 'sleep' but it only ever drops down to around 230mA. That seems fairly high. There's no under hood light but does having the hood open activate some kind of hood sensor switch that is increasing power draw?

I've also tried poking around with various fuses and there's no obvious culprit off the bat. I tried the BCM fuse too which I found some previous threads that said it was a common source because of bad door switches.

Before I go popping all the fuses out one at a time I want to make sure I'm getting a good reading at the battery, do I need to close the hood to do that? Or is there a switch somewhere in there I can manually close to make it think the hood is closed?

 

Try unplugging the hood switch.

 

The alarm monitors if the hood is open, so I expect that is where your battery drain is.

So remove a wire to the switch, or close the hood.

 

Do I have an alarm? There's an aftermarket one on the car but we disconnected it because it went crazy. Did they all come with OEM ones? There's no keyfob or anything with the car. I also don't see anything under the hood that looks like a hood switch...

 

The hood "switch" is right by the driver's side headlight mounted on a steel bracket and pointing up. If you push down on it, it should spring back up.

 

While the hood being open does draw more power, I think that the car should be able to start after 2 - 3 days with a good, fully charged battery. A 300 milliamp draw is about 200ma higher than normal, so maybe the aftermarket alarm is still monitoring. The fact that the draw drops says that the Nissan alarm is working correctly.

Things you should do: get the battery tested, it may be on its last legs. And get the battery fully charged. A jump start on a dead battery and then running the engine for a half hour is not fully charging it, so any draw on the battery will discharge it fairly fast.

 

Ok so jsut got back into town. I swear there is no hood switch. I've found pictures online that I think are of the hood switch, a circular springy thing on the drivers side front, I don't have one of those. Unless I've gone blind...

Also the battery itself seems to lose some voltage. I charged it up before I left (with the negative left disconnected), it was around 12.6V. The next morning it was at 12.47V. Just got back into town and it's still right around there. That seems partially discharged? So probably the battery is not so hot too. But also seems like something is draining it as well...

 

The voltage readings you gave for the battery are OK, but still not a true indication of battery condition. Just about all auto parts stores will do a free test on batteries, so take it to a store and get it tested.

As for the alarm hood switch, it may be that your car does not have a Nissan alarm. The alarm is listed as optional equipment, but I have never seen a car without an alarm. Does the car have a Theft Warning Relay in the box by the power steering oil reservoir?

Also, what year is the car?

 

I've heard the auto parts store battery testers aren't really all that accurate though. I was going off of this chart at the bottom of this page: https://modernsurvivalblog.com/alter...-charge-chart/

From that it says my battery is about 80% charged. Which led me to believe that maybe one cell is dead or something, since it shouldn't drop to 80% charged overnight without anything connected to it... But I still must have a drain because if I hook it up it drops much further over a few days. Time to start pulling fuses.

And I don't think I do have a factory alarm. There's no fob for it or anything. here's a picture of the area I'm pretty sure a hood switch should be and there's nothing. https://i.imgur.com/zhj0ZRN.jpg

 

Also for the record let me say, getting that bottom bolt off of the alternator - AAAAAAAHHHHHHH

 

What kind of battery and how old is it?

 

It's some autozone valuecraft battery, about 18 months old.

Might have been a fluke last time though, maybe it didn't charge up as much as I thought. Last night I put a different charger on it and charged it up until it started floating it. Measured 12.74v last night and this morning it's sitting at a proper 12.64v. So it might be ok....

Also I got a nicer multimeter but the parasitic drain measurement is still confusing me. Somehow when I put it on the A setting I get a reading of 0.3 which is 300mA. But when I put it in the mA setting I get a reading of 3. Which makes no sense. Oh well gonna get the alternator the rest of the way in and start popping fuses.

 

Hey good news! After swapping the alternator the battery drain is down to like 0.03A. Ok maybe that's not all, I also disconnected the old school broken alpine alarm siren and the power wire from the battery. One of those two seems to have fixed the parasitic draw. I'd lean towards the alarm system except I had popped the fuse out of it's power wire as part of trying to figure out the drain and that made no difference.

But hey, horrible noise is gone, battery seems to be holding a charge ok and no more drain, so I think we're good to go. Yay!

 

no it shouldnt at least. the hood for maximas as far as i know are hydrolics in which no case should drain your battery

 

You certainly don't understand the alarm system and parasitic draws. While you are correct that the hood is hydraulic, it in itself is not using power. It is like when you open the car door. The dome light come on because the door caused a switch to operate and the switch turns the dome light on. The hood operates a switch by the battery that triggers the alarm system.

 

Alternator diodes can fail.

A diode is basically an electrical one-way valve.

An alternator can drain a battery if a failed diode allows battery voltage to flow through a failed diode to the ground. It would show as parasitic draw.

Yes, a failed diode can drain a battery overnight.

Been there, experienced that with othe cars I've owned. Especially 1960s and 70s Chrysler products.

 

For some reason I keep the hood switch unplugged.

 

have you done a parasitic draw test?