Something is draining my battery

[Mr Blotto]

Any tips on how to diagnose what is draining my battery?

If I leave my bus sit for more than 3 or 4 days, it will not crank. Battery is new, terminal connectors are clean & tight.

I am an electrical novice, so please keep it basic . I have a good multi-meter, but have never used it .

Thanks!

[dtrumbo]

I have a good multi-meter, but have never used it .

Now is the time.

Most folks use only two of the three functions that makes your meter 'multi'. Probably 90% of the time it's used to measure voltage, the other 10% it gets used to measure resistance (ohms). It has a third very useful function, measuring current, but you have to do a couple of things in order to utilize this function.

As for the problem. Something is drawing current from your battery even when the key is off. The memory in your stereo draws a little, but not enough to drain the battery. If you're lucky enough to have the clock in the dash, it too will draw a miniscule amount of current, but again, not enough to drain the battery. Something else is amiss so you need to figure out what is drawing current when it shouldn't be.

Back to your meter, it will most likely have a dial where you can select which function and which range you wish to measure. In order to measure current, in addition to setting the dial to the correct setting, you will most likely need to change which hole the red probe is plugged into. The red probe is almost certainly in the hole marked V/Ohm and you'll need to move it to the one labeled mA. Then the other trick to measure current is the meter must be inline with the current flow. This is different than the way you typically think of using the meter to measure voltage or resistance. What you do is disconnect the positive cable from your bus battery. Attach the black lead from your meter to your positive battery cable and keep them from touching anything metal. Then attach the red lead from your meter to the positive terminal on your battery. Now your meter is inline between the battery and everything else so you can measure current flow.

If your battery is dying in three to four days, I'd expect you'll be reading something like 2 to 3 amps or so. Make note of the reading then methodically remove the fuses in your fuse box until the reading on your meter drops significantly. Then you'll know what general area your current draw is lurking. If the fuses in the fuse box don't reveal a problem, make sure you try the inline fuses for your backup lights and heater blower.

Come back and we'll narrow it down further. Good luck!

[Mr Blotto]

I have a good multi-meter, but have never used it .

Now is the time.

Most folks use only two of the three functions that makes your meter 'multi'. Probably 90% of the time it's used to measure voltage, the other 10% it gets used to measure resistance (ohms). It has a third very useful function, measuring current, but you have to do a couple of things in order to utilize this function.

As for the problem. Something is drawing current from your battery even when the key is off. The memory in your stereo draws a little, but not enough to drain the battery. If you're lucky enough to have the clock in the dash, it too will draw a miniscule amount of current, but again, not enough to drain the battery. Something else is amiss so you need to figure out what is drawing current when it shouldn't be.

Back to your meter, it will most likely have a dial where you can select which function and which range you wish to measure. In order to measure current, in addition to setting the dial to the correct setting, you will most likely need to change which hole the red probe is plugged into. The red probe is almost certainly in the hole marked V/Ohm and you'll need to move it to the one labeled mA. Then the other trick to measure current is the meter must be inline with the current flow. This is different than the way you typically think of using the meter to measure voltage or resistance. What you do is disconnect the positive cable from your bus battery. Attach the black lead from your meter to your positive battery cable and keep them from touching anything metal. Then attach the red lead from your meter to the positive terminal on your battery. Now your meter is inline between the battery and everything else so you can measure current flow.

If your battery is dying in three to four days, I'd expect you'll be reading something like 2 to 3 amps or so. Make note of the reading then methodically remove the fuses in your fuse box until the reading on your meter drops significantly. Then you'll know what general area your current draw is lurking. If the fuses in the fuse box don't reveal a problem, make sure you try the inline fuses for your backup lights and heater blower.

Come back and we'll narrow it down further. Good luck!

Oh Man, this is PERFECT! Much thanks for the reply - i will start testing soon and report back !

Thanks

[RSorak 71Westy]

I need to jump in on this thread as my bus has this same problem....If it sits parked undriven for more than about 5 days> DEAD BATTERY!

[Mr Blotto]

Any idea what setting I need to put the multimeter on to measure "Current"? Is it Ohms? ACV? DCV?

While nursing my hangover yesterday, I managed to hook up the meter as described, and set it to ACV. With all the fuses in the meter read in the low 20s (I think). When I removed fuse #8 (hazard switch and indoor lighting), the meter instantly went down. This didn't happen when any other fuse was removed.

So is this circut the problem, or am I doing it wrong.

If it is this circut I am perplexed. The hazard switch is 3 years old, and neitehr of my indoor lights work (the dome or the westy light over the sink).

[werksberg]

Use 12v DC (Direct Current) not AC (Alternating Current) which is your house system is run on...

[dtrumbo]

If you can, take a picture of your meter setup. Werks is right, you're trying to measure DC current, but your description (AC or DC) of the meter setting still includes V which is voltage and not current. Does the meter have any other choice that has an A or mA? Ideally, the setting would be labeled DC mA or something similar. A picture would also help verify you have the meter hooked up properly and the leads plugged into the meter in the correct holes.

[Mr Blotto]

If you can, take a picture of your meter setup. Werks is right, you're trying to measure DC current, but your description (AC or DC) of the meter setting still includes V which is voltage and not current. Does the meter have any other choice that has an A or mA? Ideally, the setting would be labeled DC mA or something similar. A picture would also help verify you have the meter hooked up properly and the leads plugged into the meter in the correct holes.

This is what I have:



I have the red probe hooked into the far right hole, and the black into the middle hole. On the car, I have the black probe hooked onto the disconnected positive cable, and the red probe hooked to the positive battery terminal.

[RSorak 71Westy]

That meter has no ammeter....You can use a 12V light bulb and socket as a replacement. Hook it up the same way as the meter, and the bulb will glow if you have a current leak, the brighter it burns the bigger the leak.

[dtrumbo]

That meter has no ammeter....You can use a 12V light bulb and socket as a replacement. Hook it up the same way as the meter, and the bulb will glow if you have a current leak, the brighter it burns the bigger the leak.

Rick's correct that your meter has no current measuring capability and the lamp is a great substitution. I never even thought of that. Great suggestion!

[twinfalls]

My trick to make sure about no drain on the battery when the bus is unused for a long time.

My battery ground strap is loosly bolted on the battery post.
Thanks to the slight cone shape of the post, it takes a 1/8 turn twist to unplug/replug the strap.
When on, the strap safely stays there ( adjust the bolt for a best fit and clean contact surfaces ).

Works as a theif retarder too, after locking the engine door.

About Multimeter measuring amps. Beware of too large currents. Most stand no more than 5 Amp.
Measuring battery current; A short or starter current will explode the meter.

[dtrumbo]

Measuring battery current; A short or starter current will explode the meter.

I suppose I should have included the disclaimer "Don't try to start the bus with the ammeter inline", but I assumed this was given.

My bus sits for up to a month between starting and I've never had a problem with the battery draining. Disconnecting the battery all the time is just masking a problem that should be fixed. Not to mention the small annoyance of your radio presets being erased and your clock being wrong. In addition, the battery cable being loose enough to remove by hand is not tight enough to make a good connection. Not trying to pick a fight with you, Twinfalls, but that's just how I see it. Everyone has their own way of doing things.

[twinfalls]

My bus sits for up to a month between starting and I've never had a problem with the battery draining. Disconnecting the battery all the time is just masking a problem that should be fixed. Not to mention the small annoyance of your radio presets being erased and your clock being wrong. In addition, the battery cable being loose enough to remove by hand is not tight enough to make a good connection. Not trying to pick a fight with you, Twinfalls, but that's just how I see it. Everyone has their own way of doing things.

My bus used at summer time starts easier when the battery had been disconected.
There is battery self discharge and I guess I have some tiny drain that should not be, because I have no clock and no radio.

For a good connection clean contact is far more important than tightness.
On a clean contact, little pressure is enough
Most battery straps, I see on cars are distorted from too strong tightening.

[Mr Blotto]

OK - I got a correct meter and hooked it up as suggested. It showed a 0.064 amp draw. I then removed each fuse as before, and #8 made the meter go to zero. I looked in the manual and #8 is for the emergency hazards and the interior lights.

I put the fuse back in (and the meter showed 0.064 amp draw again. Then I pulled out (turned on) the hazards. When I did, I heard a quick buzz for a second or two, then the flashers started to blink and the meter went back to zero!

I suspect there is something weird with the hazard flasher switch becuase only the right side markers flash with the hazard switch, but both sides work with the turn signal....

What TICKS me off is that the hazard switch IS ONLY 3-4 YEARS OLD!!!! It was the first thing I replaced when I got the bus.

Am I correct in thinking that the hazard switch is the culpret???

[dtrumbo]

Am I correct in thinking that the hazard switch is the culpret???

Maybe. Take a look under your dash at the fuse box. There are two screws that hold it in place. Take them out and gently "fold" the fuse box down so you can see the back. Look at how many wires are connected to fuse 8 and see if anyone has added any extra wiring to your bus. If it's all as it was originally, then I'd look at your flasher switch. It's odd that you've gone through a couple of them now. That might point to another issue. Is the one you put in when you bought the bus an aftermarket part or good used from another bus? I'm sure Ken at www.thebusco.com has a good used original one.

BTW, the fact that your meter read zero when the flashers were on is probably due to the fact that the autoranging function of the meter couldn't keep up with the pulsing current of the flasher relay. The fact that only the right side flashes is not good and points at your switch being hinky.