muddyford911

iTrader: (1)

Techrep, in this case we are only interested in DC amps. Amperage is the amount of current, and that's what we need to measure to diagnose why the battery is dying. Voltage is the force of the current.

Think of it as water in a pipe. Amperage is the amount of water flowing through the pipe. Voltage is the force, or how much pressure is in the pipe. In order to find out why our water tank is leaking, we need to find out how much water is escaping, and where it's coming from. Water pressure doesn't tell us much.

homer

That's right. To measure amperage the meter is being used to join the connection. In the case of my fluke meter, I have a 400ma low amperage test or 10amp test. The only caution is turn the some lights off and everything otherwise you might blow the fuse in the meter.

This is a draw test though not voltage test. So the meter joins the circuit.

The other option is a clamp on ammeter but I typically find for that low of current it won't read that (too low). This test being a parasitic draw needs the lower accuracy.

I've performed this test many times and it works fantastic. I do this with other electronic circuit tests as well as I have microcontrollers and such too but that's much different lol. Most times I've found it's aftermarket accessories that are drawing. I.e. Someone wired a relay permanently energized but switch on a circuit, or remote starts and alarms (some draw almost 200ma).

The bcm is also supposed to go into lower power state after 20 mins or so (you'll hear in some cases people say to open a door to "wake the bus") but if you're seeing 150ma you probably have an issue somewhere else. I don't want to overcomplicate this though.

Budweiser55731

Just got home from our honeymoon. Went to try the truck when I got home with pulling the fuse for the radio wouldn't turn over. So does that rule out the radio?

I'll try the other fuses once a little warmer. So with the multimeter I'll have to check every fuse or which ones would you try 1st?

muddyford911

iTrader: (1)

You need to pull each fuse out one by one, with the meter connected the way I described in my first post. Pull a fuse out, then go check the meter to see if the amperage has dropped. If not, put the fuse back in and go to the next.

The most important thing is having the meter hooked up correctly. I know I'm terrible with directions, so if it helps, bet on YouTube and look up how to find a parasitic draw.

homer

When you're pulling the fuses out, turn the dimmer switch all of the way down (force the dome light off). This way you're not waiting for the dome light to go out between tests. You don't want any other draw misleading your test results of course.


If you load the system enough during this test (i.e. you turn the ignition on), you'll blow the fuse in the meter which will disconnect the circuit and end your test. Keep everything off that you can during this test. Hook the meter up as muddyford stated, check draw (note it), then start pulling fuses one by one. My fluke meter use a 440mA and 11A fuses for current draw tests (depending on my mode selection). 11A doesn't take much to blow if you turn the ignition to on when the entire truck is running through that fuse. So just ensure nothing gets turned on during this test.


Again though, do you have anything aftermarket? remote start, alarm?

Budweiser55731

Just the remote alarm. It's what came with the truck when my uncle bought it.

I just remembered last night I put gas in this summer and the gage didn't go to full till around a half hour of driving. It's worked since. Could this be the trouble?

homer

No but there's another topic about the fuel gauge. Mine did funny things for a period of time but once I unplugged the connector under the drivers door along the frame and added dielectric grease I never had an issue again.

Don't be surprised it the alarm is draining your battery after two weeks. If you're in a low risk area, leave the alarm disarmed and manually lock the doors. See if that helps. It'll draw less power when the alarm is in the disarm state as it's not monitoring doors and such.

My 2-way compustar alarm/start draws enough power to kill my battery after two weeks. I have additional sensors though such as a tilt sensor and glass break that draw extra power. Additionally I have the iPhone start which draws even more. So I have to either plug mine into a trickle charger, use a solar panel charger, or start the vehicle once in a while to ensure it doesn't drain too much.

Warden888

Great post so far. I've dealt with this gremlin for 5 months. I use my truck only about once a week. EVERY time the battery is gone.

I have a personal friend who visited over new years that owns a battery distribution business. I mentioned to him my issues and he said "let's take a look".

First, the battery was frozen (minus temps lately). We pulled it and left if in a doorway of my home for a day. Then, connected the charger. For 3 days (8 hrs a day) we healed that battery back to life. Tested perfect and is in good form. The battery is only 3 months old (as I assumed the previous battery was just dead).

Installed the battery into the truck. He set the multimeter to DC and tested for current (as described in this thread). There was a draw of about 12v consistently. He recommended pulling each fuse to find the circuit(consistent with the suggestions here - glad to know you experts know what you're doing).

The next day (after he left) I proceeded to pull each fuse and relay to try and find the circuit. ALL showed the same 12V draw. So, I'm stumped.

Until I read the suggestion to turn off the dome lights... duh! Can't wait to go home and try this tonight (again). Will let you know.

My suspicion is the radio. It's been acting up. Another note is that this all began (not immediately, but shortly after) I did the 5.4L 3V Timing repair. Maybe coincident, but worth noting.

Thanks. I'll continue to post and review this thread.

homer

I actually was going to mention the battery freezing. When it discharged the fluids turn to water making the battery more likely to freeze.

The draw should be in amps? Are you using the DC Amps selection? I'm assuming you're flipped on volts and seeing 12v. If you were drawing 12 amps continuously, you're battery would be dead in hours (likely wouldn't be able to start in less)

Warden888

Thank you. I know it was fluctuating around 12.3 to 13. So, I'm guessing Volts. I will attempt to look at amps, but confess that while I'm fairly educated my knowledge and use of a multimeter is challenged.

I have security package. Also, the remote door locks (with the keypad on the outside of driver's door). I assume all of those things are drawing some battery while idle. My battery would die overnight (but that could have been due to the battery never really being fully charged to begin with).

I reinstalled my fully charged battery this past Saturday. Drove it half the day (morning). Been parked since and we've had very cold days of late (minus temps). Haven't tried starting it. I will give it a shot tonight and see if the fully charge battery is maintained or drained already.

Again, great advice. Thank you.