Hi guy I'm new to the forum and could use some help. I bought a 02 X back in march this year. I have a family of six and its the only SVU with enough seating and cargo room. About a month or so after I got it the battery would randomly die. I could charge it back up and it would die again a couple of days latter. I figured the battery was no good so I bought a Optima Red Top and threw that in. Truck was doing good so I thought I had it fixed. Then it started back up last week again. I could charge the battery and it would be ok for a few days then be dead the next morning.

I picked up a multi meter from Harbor Freight and checked the battery. Battery was at 10.5 volts. Charged the battery again then checked the alternator with the truck running. 14.2 volts. I've checked the connections one the battery, nice and tight not corroded or anything. My next best guess is something is getting left on and killing the battery. How do I go about testing for that? Any other ideas on what might be causing this random battery death?

 

Parasitic battery draw, searching...

 

Those trucks are loaded with lights and power points, and with 6 kids I wouldnt be suprised if something was being left on. When you get into the truck and it dont start, dont do anything, check all the map lights courtesy lights, all doors are close, vanity mirrors with lights are closed, no one put a penny in a power point, go through the truck first, then get out open hood disconnect negative battery terminal and using a test light, touch on end to the battery negative and the other to the battery cable, the light should be real dim if nothing at all. If the light is bright you have a draw and need to find it, charge battery hook up test light and pull underhood fuses out of the box intill the light goes out, than look in your service manual and see what that fuse powers, then you found out what is drawing. Magic

 

When you do this make sure the doors are closed. If a door is open you will cause a drain but since the battery is disconnected you won't see a dome light. Been there, done that. Very frustrating.

 

First, do you have a gas engine or diesel?

Stewart

 

Mine was dead every 3 days because the "Door Ajar" light on the dash was on... and the dome lights stayed on for 45 minutes every time we got in or out.

WD-40'd the door latches to get the lights to go off... then put in all LED bulbs to reduce the chances of killing the battery if they're left on.

 

I have a 5.4l gas engine

 

Ok.

On a diesel, both batteries get replaced when one goes bad, not just the one, that's why I asked.

Stewart

 

Update: Had the battery tested at Advance Auto they said it was fine. Disconnected the negative cable from the battery and put my multi meter in. The meter is set for 20 amps, initially I got a reading of 9 amps WTH! After watching the meter for a couple of minutes it went down to about 6 amps still way to high. Is this amp draw coming from the computer because it was disconnected from the battery for a couple of hours or could a bad diode in the alternator cause that kind of draw?

 

Ya she's a gas engine, thanks though Stewart.

 

Aftermarket radio can stay on, even if key is off, if they used wrong +12v source.

Aftermarket alarm system/remote start can also keep things alive and drain your battery(s).

 

The computer doesn't draw THAT much! Not even close. You shouldn't see much more than 300ma, if all lights are off, and the computers have gone to "sleep".

The alternator is a likely suspect. You can disconnect the batteries, and alt, then re-test to verify. I assume you have a DMM, and the leads are being placed in series with the battery cable? How hot is the alternator getting 10mins after a cold start, with no load?

 

It has the stock radio no aftermarket stuff same with the alarm just has the factory one.

 

Yes I have a digital, cheap one from harbor freight so I know its not the most accurate thing in the world but its not that bad either. I have the negative lead on the negative battery terminal and positive lead on the negative battery cable end. I'll have to check how hot the alternator gets after work tomorrow, for now I just left the negative terminal disconnected to keep the battery from getting killed.

 

Start pulling fuses and disconnect the alternator while doing the amp draw test . That will help narrow down the circuit . If you pull a fuse or relay and the draw goes away .... The problem is in that circuit .