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Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)
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dpilot83
Posted 3/24/2009 18:32 (#655157)
Subject: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



This is a long post I know, but if you understand electronics fairly well, I'd sure appreciate it if you bear with me. I am working on a JD 4840 that's having a problem with the battery draining overnight. It still has two 6V batteries connected in series for a 12V system.

In addition to the tractors normal electrical system I have an auxilery power box that I wired up so that I didn't need to have 5 or 6 wires running to the battery with all the monitors we have in the cab now. You can see a simple diagram of how things are set up below:

I don't have my camera with me now so I had to take a picture of the MY-68 Multi-Meter that I have with the webcam on my computer so it isn't a good picture but here is what the controls and connectors for the leads look like:

I always have the negative lead connected to the COM shown in the picture above. I have tried having the positive lead connected to the "A" (far left) and put the ammeter on the A setting which is right above Off on the right side. When I do it this way I've never seen it settle down to anything other than  -.01 to -.02. It doesn't matter if I have the other end of the leads connected in series with the ground cable and tractor frame or if they're just dangling in mid air.

If I put the positive lead in the mA hole (second from left) and set the dial to A it still does the same thing. If I set the dial to mA it reads .29 mA between the ground from the battery and the frame and it reads .02 mA between the ground for the auxillery power box and the frame.

If I put change the dial to uA (I don't know how to make the symbol for micro amps.....10-6 amps) it says 256 uA between the ground from the battery and the frame and .2 uA between the ground for the auxillery power box and the frame.

Between the auxilery power box ground and the frame the reading is always negative. Between the battery ground and the frame the reading is positive if I put the positive lead on the ground stud on the frame and negative if I put the negative lead on the ground stud on the frame. I don't understand that.

I also don't understand why it appears that there is a much larger draw between the battery negative and the frame than the auxilery power box negative and the frame, but if you rub the ground cable for the battery against the stud it does not spark and if you rub the ground cable for the auxilery power box against the ground stud it does spark (small sparks but sparks nonetheless.

I also thought that all of the power draw that I've seen is well below what would drain your battery but maybe I'm wrong. What is the maximum allowable drain for this type of a thing?

Any help you can provide would be much appreciated. Thanks.

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Jon Hagen
Posted 3/24/2009 19:02 (#655195 - in reply to #655157)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



Hagen Brothers farms,Goodrich ND
Pretty hard to help without knowing the quirks of your meter and the exact system wiring,
All I can say is go low tech and use a 12V test light, Any load that will drain those batteries overnight, will light a test light. Disconnect the ground cable from the neg battery post and connect the 12V test light between them.
Now start disconnecting electrical items until the light goes out.
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farmhowe
Posted 3/24/2009 19:11 (#655206 - in reply to #655195)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)


alternators can be a stinker to find but still be able to drain over night. You can use the test light or just un hoop the alternator and leave it set over night and check it in the morning. I have seen this problem several times on our 4640, 4430, and 4230 deeres.
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K in Iowa
Posted 3/24/2009 19:35 (#655234 - in reply to #655157)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)


To measure amperage, the meter must be in series with whatever you are measuring. The meter essentially is measuring the electrons going through it. If you are on the current settings and measuring between two points without disconecting a lead and getting in series with it your readings mean nothing. If you are in series, you may just be seeing noise on the system. You are correct, microamps of drain is really no drain at all.
If you have the meter in series, here's a couple of things to check.
1. Does the meter have a fuse in it? Typically these are in the battery compartment. It's there to protect the current measurement from overload. Very easy to blow these.
2. Alternators and starters sometimes cause a current "leak" that can drain batteries. Disconnect them and let it sit overnight. If one of them is the source of the leakage the batteries will still be up in the morning.
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dpilot83
Posted 3/24/2009 19:39 (#655240 - in reply to #655234)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



I have been connecting it in series which involves removing the nut that holds the grounds to the stud and then removing the grounds and then connecting one lead to the cable and the other lead to the stud.

1. I'll check the fuse. It says it has a 10 amp rating.

2. Is this current leak something that would not be noticed by the test light or ammeter test?

Thanks
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dpilot83
Posted 3/24/2009 19:43 (#655243 - in reply to #655157)
Subject: Multi-Meter Directions



I can imagine that some may be wondering why I don't just read the directions on the meter. This would be an understandable question. The problem is that I lost them. I looked on the internet to see if I could download them anywhere and you cannot but I did find many people who said that the directions that came with the meter were very close to worthless because it was made in China. I looked on the website for tech support and the number is a Hong Kong number so that isn't an option either. I'm wondering if I should just buy a better multi-meter.

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dpilot83
Posted 3/24/2009 20:03 (#655259 - in reply to #655195)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



Thanks for the input. All I had for a test light was a brake light bulb that had wires soldered on the terminals. It was hard to ensure that I had a good connection at both places (not enough hands) but I think I was getting a good connection and the test light never went off with either of the two ground cables. I'll probably rig the light up a little better to make it easier to ensure that I'm getting a good connection but between that and the incredibly low readings on the multi-meter I'm beginning to lean towards either the alternator or starter causing problems like one of the other posters said. Is there a way to test those problems (other than waiting overnight with one of them disconnected and then waiting the next night with the other disconnected)?

Edited by dpilot83 3/24/2009 20:04
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dpilot83
Posted 3/24/2009 20:08 (#655269 - in reply to #655206)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



When you say you can use the test light do you mean that you can hook the test light up in series with the alternator just like I was hooking the multi-meter up in series with the ground for the tractor? Or are you saying that by hooking the test light up in series with the ground of the tractor I can find the alternator problem? Thanks.
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Jon Hagen
Posted 3/24/2009 20:12 (#655275 - in reply to #655243)
Subject: RE: Multi-Meter Directions (EDIT)



Hagen Brothers farms,Goodrich ND
dpilot83 - 3/25/2009 18:43

I did find many people who said that the directions that came with the meter were very close to worthless because it was made in China. I looked on the website for tech support and the number is a Hong Kong number so that isn't an option either. I'm wondering if I should just buy a better multi-meter.



LOL, reminds me of the warning decal on the China built electric motor on my 25 year old band saw.
It said " WARNUNG !!!, volt of wrong volt, this motor will broken" I suspect that translates to, " This sucker is wired for 120V, if you plug er into 220, she's gonna blow up big time" LOL.

Any drain that will kill batteries in 24 hours will show on a test light.

A brake light draws several amps, a bit much. A salvage side marker light out of a 70's Ford product or an auto parts store test ligh has a small bulb that will need only about 1/4- 1/2 amp to light, so will detect a smaller leak..

Edited by Jon Hagen 3/24/2009 20:27
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RickB
Posted 3/24/2009 20:14 (#655278 - in reply to #655243)
Subject: RE: Multi-Meter Directions



New York's Hudson Valley
Another useful tip is that some processors draw pretty good at powerup, then level off to a reasonable amount when "off". Problem is, it is easy to pop a fuse on the multimeter during the power up phase if the meter is set on the milliamp scale. I bridge the connection with a separate wire where the meter will be installed, then install the meter in parallel with the wire, then remove the wire and read the draw. My comfort level is about 25 milliamps total draw on a tractor's batteries. Much over that is going to lead to dead batteries in not too long a time.
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dpilot83
Posted 3/24/2009 20:22 (#655289 - in reply to #655278)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



That is a good idea. I believe that may be why I'm seeing sparks when I rub the ground from the auxiliary power box against the stud on the tractor frame (I've been saying tractor frame all this time but it's really on the block of the engine....not that it matters all that much). Anyways, the Insight is connected to the auxiliary power box and when I had another person in the cab while I was touching the ground cable to the stud they said the Insight screen would flash a little even though it was off. Because of this we've been thinking that the Insight has been causing the problem but that has been in disagreement with the multi-meter because the multi-meter was saying that there was less draw on that circuit than on the main battery ground.

After you would touch it to the stud and then remove it, you could touch it again and it wouldn't spark near as much. It's like there is something in the Insight that's charging up or something and takes several seconds to draw down enough to create a spark the next time you touch it.
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Jon Hagen
Posted 3/24/2009 20:36 (#655318 - in reply to #655289)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



Hagen Brothers farms,Goodrich ND
dpilot83 - 3/25/2009 19:22

That is a good idea. I believe that may be why I'm seeing sparks when I rub the ground from the auxiliary power box against the stud on the tractor frame (I've been saying tractor frame all this time but it's really on the block of the engine....not that it matters all that much). Anyways, the Insight is connected to the auxiliary power box and when I had another person in the cab while I was touching the ground cable to the stud they said the Insight screen would flash a little even though it was off. Because of this we've been thinking that the Insight has been causing the problem but that has been in disagreement with the multi-meter because the multi-meter was saying that there was less draw on that circuit than on the main battery ground.

After you would touch it to the stud and then remove it, you could touch it again and it wouldn't spark near as much. It's like there is something in the Insight that's charging up or something and takes several seconds to draw down enough to create a spark the next time you touch it.

You need somthing on there that will indicate a constant drain, like a small test light.
Most alternators have an internal electrical noise filter capacitor. This capacitor will draw a bit of power for a second when power is first connected to the big "BAT" stud on the alternator rear. This will cause a tiny blue spark when that wire touches the stud as the capacitor charges up then takes no power after that. This leads people to falsly believe the alternator has a short, when actually nothing is wrong. Any other accessory with a built in filter cap in the power leads will do the same thing.
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Indianajones
Posted 3/24/2009 20:38 (#655321 - in reply to #655157)
Subject: RE: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



I will apoligise that I am not following really well what you are connecting hwere with the meter. I have chased alot of parasitic draws in my career as a GM technician. If i was going to test, I would connect the meter between the battery negative post and the cable from the frame.
If i am reading correctly in the second paragraph beneath the meter picture, this is what you did and the reading was.29mA and .02mA between the box and the frame. This indicates to me that the draw is not from the box but the rest of the system.
I would install the meter between the battery and cable as discussed above and test the dram. Then disconnect the power box positive and see if it goes away. If not, then start pulling fuses and disconnection electrical loads on the rest of the tractor.
GM used to claim spec for parasitic draw was 25mA draw as the max allowed. If you get up into the 250mA area, it can drain a battery overnight. You stated a draw as .29 mA, is this .29 or 290mA? If the meter is auto ranging, they can be decieving.
Hope this helps.
INDY
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dpilot83
Posted 3/24/2009 20:49 (#655341 - in reply to #655321)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



I will go check again to try and figure out if it's pulling any auto-ranging stuff on me. My assumption is that the .29 mA is correct because I have been unable to make a test light show even the tiniest bit of light. My test light is a brake light though so maybe that's too big for the stuff that I'm looking for.

I may not get to work on this anymore tonight. I'll post back tomorrow though. Thanks.
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dpilot83
Posted 3/24/2009 20:52 (#655345 - in reply to #655234)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



I took the multi-meter apart and found that it has two fuses. One 10 amp fuse for the amp lead on the multi-meter and then a much smaller 300 mA fuse for the mA lead on the multi-meter. I did a continuity check on both of them with another analogue meter and they were both good.<br />

Edited by dpilot83 3/24/2009 20:53
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dpilot83
Posted 3/24/2009 20:55 (#655355 - in reply to #655318)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



I will try to get a proper test light. I wonder if my brake light bulb is too large to see the drain that I'm looking for.
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dpilot83
Posted 3/24/2009 21:18 (#655402 - in reply to #655275)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



I caught your edit. I was hoping someone would comment on that. Thanks.
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School Of Hard Knock
Posted 3/24/2009 21:34 (#655444 - in reply to #655157)
Subject: RE: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)


just a tish NE of central ND
I second using the test light. Put the probe test light on the positive battery post and the lead of the test light on the positive cable and if there is a battery drain it will illiuminate the bulb. Unhook stuff untill it the light ceases. It should find you problem.
My last deal I used a light to test finally turned up a fault of a previous reapir from a local cenex station. The double wire end on the alternator was wired up exactly backwards.(new end installed wrong)
good luck
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farmhowe
Posted 3/24/2009 21:47 (#655470 - in reply to #655259)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)


feel the alternator if you have not run the machine for a while, if the alternator is warm then it is bad and that is where your feed is
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dpilot83
Posted 3/27/2009 09:52 (#658483 - in reply to #655157)
Subject: Re: Electrical Gurus - Mastech MY-68 multi-meter (battery drain diagnosis)



To everyone that helped out on this, thanks. We've discovered some weird things that are going on and there will probably be a post in the precision ag board in a few days. For now though we've discovered that one of the 6V batteries has a cell that is bad only intermittently. We had the battery that we suspected totally disconnected from the electrical system of the tractor and put a load tester on it and it was fine. We decided we were going to replace it anyways and we moved the batter to a different position away from the tractor and tested it again out of curiosity literally 30 seconds later and it was running 4 volts without a load and essentially nothing under load.

That being said, we're pretty sure that's not all of the electrical problems with this tractor and as I mentioned, I'll probably be posting more questions in the precision forum later. Thanks again.
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