ok, i'm not super fimiliar with diode check mode, but from what i gathered off of google, i tested a good Double A battery and got 1.2 and i tested the JD battery another nothing, just 1. this is with it out of the tractor as well. does this sound right?
trouble with 4410 starting
- Thread starter NGA
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JD755
Platinum Member
So you are saying that with the meter in normal mode to read voltages, the battery only reads one volt when it is out of the tractor. That's a significant failure caused by something. Did you check under the cell caps for acid level? Alternator/regulator problems could have boiled it dry. Or it might not have been properly filled to start with. Do you have a battery charger to see if it will take a charge? If it can be charged again, you may be able to start the tractor long enough to measure charging voltage. However, many modern battery chargers will not activate if the battery voltage is only one volt to begin with.
There could be a fault in the alternator that is draining the battery full time even when the key is off. Was there a significant spark at the terminal when you first connected the new battery? That could indicate a large current draw from a short.
There could be a fault in the alternator that is draining the battery full time even when the key is off. Was there a significant spark at the terminal when you first connected the new battery? That could indicate a large current draw from a short.
when i read DC v with the multimeter out of the tractor i get 12.54v. when i goto the diode check mode on the multimeter i get 1. it is quite possible i am doing somethinig wrong as i have never done that before. here is the link i used to check the diode
Meter check of a diode : DIODES AND RECTIFIERS
Meter check of a diode : DIODES AND RECTIFIERS
JD755
Platinum Member
Diode check mode is not used to test the battery. In that mode the meter is providing voltage to the leads to check directional continuity of a circuit. This would be for connecting to the battery cables without the battery connected, looking for a short on the tractor.
JD755
Platinum Member
I would just start with the meter in standard ohms settings. Connected across the cables it should not show a low resistance on any range. Then reverse the leads and check all ohm ranges again. Record your readings. The lower meter ranges will typically provide higher current level (still very low) to the leads. One of those lower ranges may even have a diode symbol indicating that. That just has to do with providing enough current to activate diodes in the circuit but I don't think that's a concern here. Sounds like we are looking for a short that will show up on any range. That diode check could be used later for troubleshooting the alternator/regulator diodes.
arrabil
Veteran Member
On my Fluke, you use diode check mode for determining connectivity. When you touch the probes to two points without connectivity, the display reads a steady "0L". If they have connectivity it changes to "0.0003" or similar and it'll jump around.
NGA, figure out what your two different displays for connectivity and no connectivity are, then with everything hooked up, see if you show connectivity between positive and ground in a few places (including the battery). If you do, there is definitely a short.
JD755
Platinum Member
You are using it as a basic continuity tester and that's not really what diode mode is for. It is the same as all those other ohm ranges, but provides sufficient current to cause a junction diode to allow the current to flow through it. Other ranges may not provide that, and provide a false check of a semiconductor component. For example when connected to a good diode it should show conductivity in one direction and not in the other. Insufficient current testing could falsely show no conduction in either direction.
By using the various ohms ranges you can determine if the tractor has a continuous load connected, and how much. 100,00 ohms is not a problem, but 100 ohms would be. Just looking for continuity may not show that 100 ohm load.
Any meter should never be connected across a voltage such as the battery when in ohms mode. It is a low impedance load then and can be damaged from the excess current through it.
Edit. Some meters, as shown in the link from NGA, may also have a dedicated " Diode Check" switch position on the meter. This would not be one of the resistance ranges, but a separate position with no number markings. That position cannot show resistance, but is used to show the voltage drop across a diode. For troubleshooting, it definitely is only good for working directly on semiconductor components.
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