Jump to content
Save Old Iron

Locating Parasitic Battery Drain

Recommended Posts

Good question from one of my star students, Horsefeathers. :ychain:

Question?... How do I use a Multimeter to find a slow drain on a battery?

If I drop the neg cable it's fine, if I leave it hooked up 3 days bat is dead!

I know the analogy that electricity flows like H2O but mine is going down the drain!

Wanted to trade... Dunce Cap for Graduation Cap!

cool.gif HORSEFEATHERS!

Let me create a few visual aids and we will have the culprit tracked down in no time.

Be right back.

Share this post


Link to post
Share on other sites

Here you go Bud,

parasitic.jpg

Essentially, you need to lift either the ground wire or the positive cable leading from the battery terminals and insert your meter set to read DC amps in series with the remainder of the tractor wiring.

READ YOUR METER INSTRUCTION MANUAL ON HOW TO SET THE METER FOR DC AMPERAGE AND WHICH METER SOCKETS YOU NEED TO INSERT YOUR MEASURING LEADS INTO TO MEASURE CURRENT.

The sockets for current are different than the sockets to measure voltage and ohms. This is true 99% of time on multimeters.

SET THE METER TO READ THE HIGHEST CURRENT POSSIBLE - USUALLY 10 AMPS ( some meters have a 20 amp scale). THIS IS DONE TO PROTECT THE METER FROM BLOWING AN INTERNAL FUSE IF THE CURRENT THRU THE METER EXCEEDS THE METER RANGE.

If the parasitic current is less than 1 amp, the meter may not register any reading on the 10 map scale. It is then safe to switch the meter to read on a lesser scale for DC amps - say 200 milliamp (.200 amps).

Hook up the meter leads in your tractor like in the diagram above. The parasitic current will actually be flowing thru the meter body.

Let's say for the sake of conversation, the parasitic drain is in the headlamp circuit.

We hook the meter up in the positive battery cable circuit, note the meter reading and it is .3 amps - so we have a 300 milliamp (.3amp) parasitic drain.

Now lets look at all the components current will flow thru in the above diagram.

Starter solenoid , ignition coil, and lighting circuit.

Start by removing the blue wire from the starter solenoid - no change in meter reading - no parasitic current flowing thru the solenoid. Replace the blue wire.

Lift the orange wire from the ignition coil - multimeter reading remains at .3 amps.

So no parasitic current is flowing thru the ignition coil. Replace the orange wire.

Now we come to the headlight / taillight circuit. Lift the Green wire from the headlight

Multimeter indication drops to zero amps - you found the circuit the parasitic current is flowing thru.

Now, if you have taillights parallel wired of headlights, disconnect the headlights. Still have .300 amps on the multimeter readout - well sir, you have unwanted current flow to the taillights. Time to take a visual look at the taillight wiring / taillight housing.

If you let me know what model tractor you have, maybe we can pull a wiring schematic and start to highlight the different current paths in that particular model.

Please say its not a 520H !! :ychain:

Good question - thanks for starting a good thread.

  • Like 2

Share this post


Link to post
Share on other sites

Now that's an excellent tutorial. :ychain:

Bob

Share this post


Link to post
Share on other sites

again chuck you gave a no BS good tutorial that explains some much with so little! thanks

Share this post


Link to post
Share on other sites

Great post Chuck, even I understood it. Now I need to get online and search a manual for the meter a friend gave me a couple years ago. I don't want to blow the thing up trying to use it. :ychain:

Share this post


Link to post
Share on other sites

If it's on an older Horse with a cigarette lighter take a good look at that. I used to have dozens of them get the elements corroded and short together on cars causing a dead battery when I was in the Auto business. I could imagine what an old 40 yr. old lighter element would look like on a tractor that has spent it's life exposed to the weather! icon_cold.gificon_snow.gif

Share this post


Link to post
Share on other sites

I'm going to install a "THANKS S-OI-" button on my computer keyboard since I need to use it so often. S-O-I, how would I do that? :ychain:

THANKS S-O-I !! :D

Is there going to be a test? Your tutorials are so concise, I'd probably pass it! Shazaam!!

Steve

Share this post


Link to post
Share on other sites

If it's on an older Horse with a cigarette lighter take a good look at that. I used to have dozens of them get the elements corroded and short together on cars causing a dead battery when I was in the Auto business. I could imagine what an old 40 yr. old lighter element would look like on a tractor that has spent it's life exposed to the weather!

Speaking of older Horses and parasitic leaks:

Wheel Horse Service Bulletin #102 Covers 1968 tractors with 10 Amp alternators. As manufactured these have the regulator connected to the battery at all times.

This bulletin covers replacing the 4-terminal ignition switch with a 5 terminal switch. The rectifier gets connected to the R terminal. This serves to isolate the charging system when the switch is in the off position.

:D :ychain:

Share this post


Link to post
Share on other sites

:ychain: for asking this question Horsefeathers and :D for the excellent detailed and easy to understand answer Chuck! I know for a fact that this information is going to come in extremely handy for me.

John

Share this post


Link to post
Share on other sites

SOI is 110% on blowing the internal fuses...don't ask me how I know!

Share this post


Link to post
Share on other sites

Bravo! Straight-forward, to the point, and no BS! :ychain:

Share this post


Link to post
Share on other sites

Hey i havent Read all of this forum but i would like to Add my way of Locating a Draw is with my Snap on Test like It will not work unless there is more then 6 volts presant It would be a Quick way to locate the source in my opinion The differnce is Cars are supposed to have some what of a Mili amp draw I guess wheel horses shouldent have any Hope i dident loose anyone I like the Scematic up there I would go with that and start with test lite and known good ground and then breack out the volt meter Just my two cents

Share this post


Link to post
Share on other sites

Old_Iron, Thanks for the easy to understand info!

I don't think we can find a schematic as this is on the "603 Gasser"

It was built with components and wireing from another custom,

So I have no idea what model the oridginal donor is!

No lighting curcit, so with your information it should be easy to track down!

Thank You!

:ychain: HORSEFEATHERS!

Share this post


Link to post
Share on other sites

Another source of slow battery drain that can drive you bonkers is a build up of damp crud on the outside of the battery case. This film can conduct just enough current to drain a battery fairly quickly.

Since your drain can be stopped by unhooking the ground cable it is probably NOT your problem, just thought I'd throw it out there for general info.

Share this post


Link to post
Share on other sites

No lighting curcit, so with your information it should be easy to track down!

Thank You!

:ychain: HORSEFEATHERS!

Please, Please, Please, Please, Please, Please,

check the battery first. Do a load test before going too crazy with any other troubleshooting.

If your dealing with a heavily sulfated battery, the little charge it does accept will self discharge over a few days - all by itself without help from any parasitic drain.

A good battery will easily hold up to a considerable parasitic drain, even over a few days.

Share this post


Link to post
Share on other sites

Another source of slow battery drain that can drive you bonkers is a build up of damp crud on the outside of the battery case. This film can conduct just enough current to drain a battery fairly quickly

I want to second this. At least once a year you should you should mix up about a quart of water and several tablespoons of backing soda. Brush it on the top and side of the battery and in the battery tray. Make certain not to get any of this down the vent holes in the caps. Keep brushing until it is clean and not foaming. Rinse with lots of clean water.

If you are really lazy, just blast it with the garden hose. Of course this could get water in places you really don't want water!

Share this post


Link to post
Share on other sites

Battery load tester! Yes Yes Yes! You have mentioned that before!

I'll pick up one of those at HF! I hear they are good for all the more they cost!

Hydrometer shows 2 cells low even after 2 amp overnight charge!

That may be the problem right there! (Sulfated who'da thunk it?)

Guys, if you don't ask you can't learn! I'am learning something now!!!

Thanks Chuck!

:ychain: HORSEFEATHERS!

Share this post


Link to post
Share on other sites

That may be the problem right there! (Sulfated who'da thunk it?)

Bud, good find on the 2 low cells.

You can still make the current measurement off the battery even with a defective cell or two in the battery.

You may in fact have a parasitic drain. A quick measurement will confirm this one way or the other.

Share this post


Link to post
Share on other sites

Chuck, I have a good battery I can install for the test.

Or should I use the old battery?

The 603 is in COLD storage but I'am courious to check this out!

I'll try it this thursday as I'am off work for holiday!

Bud!

Share this post


Link to post
Share on other sites

I would like to thank SOI for this thread/tutorial as I have just used it and my DVOM to locate a drain on a non Wheel Horse tractor.

And I would like to tell you all as the culprit I thought unusual. The battery is virtually new. If I ran the tractor every couple of days it would always start. Let it sit for a week and the battery would be completely dead not a click. I tried the old test light to the ground cable circuit and it did not light. I thought well the batt must be bad, bum cell or something. After reading this thread I decided as soon as I can I'll try the DVOM. Using the meter in the 10A position, red lead to pos batt post, black lead to pos batt cable and I had a reading of 00.06 which I believe is

6 hundredths of a volt.

So down the line I go looking. The main feed wire for this tractor goes from the pos batt cable on the solenoid directly to the ammeter with a circuit breaker in between, out of the ammeter to ign switch. I disconnect the feed into the ammeter and reading is 00.00 of course, for there is no load now, hooked the wire back on the ammeter and the 00.06 was back. I disconnect the other wire on the ammeter and do my test again and I have 00.05. Wait a minute, taking this wire off there should be no load. Looked at the nylon insulators thru the mounting bracket and all were there. I removed the ammeter and with the DVOM now set to check ohms/ resistence I touched one lead to the ammeter case and the other to a term and had continuity, then the other term and same. There should be not continuity between these terms and the case.

Next I went back to the tractor and with a machine screw and nut joined the two wires for the ammeter together. Put the DVOM back in the 10A postion and did my test at the battery and cable again, my reading was 00.00.

So the culprit/sap/drain was the ammeter. Thanks for reading, Richard

Share this post


Link to post
Share on other sites

Great troubleshooting Richard :banghead:

glad this post helped you out.

It might be really interesting to crack open the case on the ammeter and see if there is a significant amount of corrosion or moisture inside the ammeter case.

or

Maybe place a hair dyer on the ammeter for 15 minutes to heat up the inside of the gauge and dry out any trapped moisture. Then check the resistance again from case to the terminals ?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Recently Browsing   0 members

    No registered users viewing this page.

×