Voltage drop at solenoid - how much is too much?

[finfan1313]

I have a John Deere X320, and ever since I got it, I've had to jump start it almost every time I use it. I took the battery in, and the dealer told me it was fine (and that I'm out of warranty), and that I'd have to bring the whole mower in to get it fixed. I'm trying to do it myself, and am hoping to find what's causing the draw on the battery. I did some testing on the solenoid, and here's what I read at the battery and solenoid (4-pole). The black cable was removed from the battery to do these tests:

at battery: 12.32 Volts
Pole 1: from battery to solenoid - 12.32 Volts
Pole 2: purple wire pole at solenoid: 11.66 Volts
Pole 3: Other large nut with red wire: 11.66 Volts

I also checked at the starter, and it's getting 12.32

Generally, If I run the mower for an hour or so after a jump, and then I start it again right after I'm done, I can start it once. However if I wait a week, I get a few clicks, then it gets weaker and weaker until I get nothing, and the battery tests at about 3-4 volts before a jump. Could this be a bad solenoid? I checked the connection at the seat switch, which was dirty so I cleaned it, but the seat switch appears to work fine while I'm mowing. I'm sure it must be something fairly simple, but am trying to avoid spending a couple hundred $$ at the dealer.

Thank you!

 

[SeniorCitizen]

finfan1313 QUOTE: I read at the battery and solenoid (4-pole). The black cable was removed from the battery to do these tests:
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You may get more response if you would explain how any voltage is being read with your meter when the black cable is disconnected from the battery.

 

[finfan1313]

finfan1313 QUOTE: I read at the battery and solenoid (4-pole). The black cable was removed from the battery to do these tests:
**************************************************************************
You may get more response if you would explain how any voltage is being read with your meter when the black cable is disconnected from the battery.

Thank you for the helpful hint Senior. I turned the multimeter to Volts, 20. I put the black probe on the black battery terminal, and the red one at different places on the solenoid, or battery, depending on which part I'm trying to test. I posted above what numbers show up when I do that.

Should I do the readings again with it connected? I was under the impression the black cable should be disconnected.

 

[motoman]

Despite your dealer saying the battery is fine we do not know what that means. Does a dash ammeter show charging (positive) while running? Had you charged it up? Checked the electrolyte specific gravity with a battery hydrometer ($3 in an auto store)? Had load test done (see if battery will hold voltage above 9V while cranking load is present)? If so and battery is good why not run a battery current drain test with your multimeter set on "current?" That will show if truly something is draining the battery. Use the search function to find lots of technique and findings on this test.

 

[Rivets]

I had something very similar to this two weeks ago. Try this trick to see if anything changes. The next time you finish mowing and have a fully charged battery, remove the B+ wire from the voltage regulator. The next time you use the unit, reconnect the wire and see if it will start. If it starts your battery is being drained by a bad diode in the voltage regulator, with is allowing the battery to drain even though nothing is on.

 

[finfan1313]

I had something very similar to this two weeks ago. Try this trick to see if anything changes. The next time you finish mowing and have a fully charged battery, remove the B+ wire from the voltage regulator. The next time you use the unit, reconnect the wire and see if it will start. If it starts your battery is being drained by a bad diode in the voltage regulator, with is allowing the battery to drain even though nothing is on.

Easy enough, I'll try that. Thank you!

 

[finfan1313]

Despite your dealer saying the battery is fine we do not know what that means. Does a dash ammeter show charging (positive) while running? Had you charged it up? Checked the electrolyte specific gravity with a battery hydrometer ($3 in an auto store)? Had load test done (see if battery will hold voltage above 9V while cranking load is present)? If so and battery is good why not run a battery current drain test with your multimeter set on "current?" That will show if truly something is draining the battery. Use the search function to find lots of technique and findings on this test.

I don't have a dash ammeter, but it does appear to charge while running, as it will occasionally start again if I start it again soon after I finish mowing. I did a battery current drain test with the multimeter set on 20ma and got a reading of .89ma.

I did not check electrolyte gravity or do a load test. I charged the battery on Saturday and disconnected the black battery cable, and it's not lost any charge since.

Any other ideas you can provide would be greatly appreciated.

 

[finfan1313]

I had something very similar to this two weeks ago. Try this trick to see if anything changes. The next time you finish mowing and have a fully charged battery, remove the B+ wire from the voltage regulator. The next time you use the unit, reconnect the wire and see if it will start. If it starts your battery is being drained by a bad diode in the voltage regulator, with is allowing the battery to drain even though nothing is on.

Question. Is the B+ wire the red one? Mine has 2 wires together, and connected to the left two tabs, and the third tab, on the right, is the red one. From what I see online though, it seems the B+ is in the middle on most voltage regulators.

It does appear there's a draw on the battery based on my draw test, and it appears this is the most likely culprit.

 

[motoman]

The 89 milliamps seems high to me but pros must chime in here. I always think of older cars expecting about 50 milliamps normal, but that can vary. Since tractors seem to have less stuff (if any?)running when the key is off I would not expect 89 milliamps, but... Anyway if you are being drained in less than the 3 week interval perhaps something more drastic is going on like Rivets says. But 89 will pull down the bat over time. You are not accidentally leaving on a light? Also the other day I was reminded about drain after I accidentally left the ignition key "on" after a full float charge on my dyt4000. It needed charging the next morning , but nothing drastic. I had removed the time meter long ago. So I guess current was only circulating to turn on stuff like little transistors which use very little.. IMO

Edit: Your reading 89 milliamps or 8.9 milliamps? Or as stated less than 1 milliamp? Latter two say "no significant drain" IMO

Edit: Or perhaps my small drain was from the two electric gauges I added, oil pressure with sender and oil temp with sender. Both probably circulate a very small current thru the sensors and gauges, but only when ignition is on.

 

[bertsmobile1]

Finfan,
You sound like a reasonably intelligent person so I will give some some very intelligent advice.
GO to the John Deer web site and buy the technical manual for your mower.
It will pay for itself in beers & sound sleep alone let alone the hair transplant to replace what you are tearing out.
Everything is carefully explained, what is there, how each bit works , how to test each & every part and more important what order to test them in.
If you don't want to fix the mower properly in an hour or so then you can lift the mower up onto the highest jackstands you can find.
Late at night in the dark pull each & every plug off while looking very carefully for a spark.
Some rectifiers need and thus draw a tiny amount of power all the time and some hour meters also have a fixed power draw.
However as I don't know which ones your mower has & I don't have a wiring diagram for your mower I will just be guessing.

The middle wire from almost every rectifier is one of the DC outputs, usually the + the two outside wires if they are the same colour will be the AC input on most rectifiers used on ride ons the case is the ground terminal and also the heat sink.

As previously stated the diodes in the rectifier can go bad and when that happens several things occur depending which diode is blown.
1) you get pulsed DC output which can be reversed and wreck the battery.
2) you can get pulsed DC that will not be enough to recharge the battery
3) when not rotating the alternator tries to be an electric motor and drains the battery.