12 volt drain on my ZD28F

[JimDD]

I have a nuisance but undiagnosed 12V drain on my battery. I have replaced the regulator, key switch, both main 12V cables and checked and cleaned all of the connection points. Battery does charge up to 100% with a battery charger and has been verified as good by Oreilly Auto where I bought it.

Problem comes when I stop cutting, the mower won't start up again and the battery is down to 78% charge and has to be recharged to start the mower up again. The starter is brand new also.

I have taken the dynamo off and had it tested by an alternator shop and it shows it is functioning. Is there anyone who has had similar problems such as mine? Any help would be appreciated.

 

[Daren Todd]

It actually could be a couple of things. The biggest issue is your gonna have to narrow down where the drain is coming from.

First thing is to double check the battery. The digital testers they use at the auto parts store are hit and miss depending on the issue with the battery. I use an analog load tester on battery's as well as checking voltage for a drop over time with out anything hooked to it. With the unit not running, disconnect the ground cable, take a reading with a digital meter. let it sit for about a 1/2 hour and check again. If there is a small drain on the battery, it will drop around .1 volts over 30 seconds to a minute depending on how bad the battery is. If the unit has been running, then let it set a half hour before testing for the voltage to equalize. If the battery does have a slow drain with the ground cable disconnected, then the test at the auto parts store missed the fact the battery has a small internal short.

If the battery tests good, then I start moving down the line to see where the drain is coming from. First I disconnect the main power wire to the starter. Check voltage, and if you still have a drain, then it's between the battery and starter.

If no drain, I hook that wire back up, then disconnect the alternator and check again. Working my way through any relays switches and and electrical components such as a dyno, regulator, and starter, or alternator.

Relays can corrode and stick partially inside, and can cause a slow drain. As well as water or corrosion in a quick connect along the wiring harness.

Good luck and keep us posted. Sometimes those drains are easy to find, sometimes they can be a bear

 

[Tooljunkie]

Battery tests good dynamo tests good starter newish. So there should be no problem. Voltmeter on dash is your next step.
Battery % tells me nothing. Voltage.either you have it or you are losing it somewhere.
Key on nothing running, 12 volts need to be present.
Cranking,voltage need to be no less than 10 volts.
Running,voltage needs to be minimum 1 volt above whatever voltage you began with.example, key on 12.4 volts,then running voltage should be 13.4.

If i read correctly,battery is running down while mowing. Then likely there is a break in your charging circuit.

 

[1970cs]

I will agree that it does not sound like a drain by your explanation! When you hook up a multimeter set to volts, what is it showing for voltage at high rpm's?

Pat

 

[lugbolt]

Kinda long but bear with me. First thing's first. 78% charge means nothing. You're looking for 12.8v or higher at the battery with no load on it (disconnected). You can load test it too, using the starter. Hook the cables back up, put your digital volt meter on the battery and have someone crank the engine. You don't want to see anything under about 10 volts. And those voltages are measured on a fully charged battery! Less than 10v loaded, your battery is weak. Autozone's battery test is junk! All parts stores are. The only TRUE battery test is with a digital volt meter and the machine that the battery is powering! There are some expensive battery testers available-I have one-and even those sometimes will give a "false" test result.

ASSuming the battery is "good"....do a charging system test. Put digital volt meter probes on the battery + and - posts and start the engine, running wide open throttle. You should see around 13.5 to 14.2v. If not, you're going to have to investigate your charging system and wirings.

Then ASSuming the charging system is working properly, remove ONE battery cable, doesn't matter which. Take your DVOM (digital volt-ohm meter) and put one probe on the battery post, and the other on the cable you just took off. Key off obviously. Read the DVOM voltage. You don't want to see much if any voltage. 1 or 2 volts is fine. If you're seeing 11v to 13v (again key off), you have a voltage "draw". To find your "draw" source, you can remove each fuse one at a time until your draw goes away (DVOM back to 1 or 2 volts). Once you've isolated which circuit is drawing, take a look at the WSM and follow the circuit, to see which components are on that fuse's circuit. Disconnect each component with the fuse back in and watch your DVOM; when you disconnect something and draw goes away, you found your problem.

 

[JimDD]

Well, whatever winter Louisiana had has come and gone. LOL

But, I removed the battery again before its warranty ran out and had Oreilly "test" it. Still shows to be a good battery.

That said, I did the repeat tests on the voltage and found intermittent drops of voltage. I was about to order another dynamo. When I removed the dynamo from its location, I noticed a bit of dust that shook out of the housing inside. Since I was going to order another one, I decided to open this one up and see what gives. It is a two wire dynamo.

Long story short (and I still may have to replace it) is that I found enough caked dust inside that I hardly could recognize the parts within. I cleaned all the dust out and shined the surfaces including the steel rotating surfaces to a bright finish. Put the thing back together. It felt different with the magnets seeming to be in more resistance when turned by hand.

So, warm weather is here and I am about to find out if I did any good. I will update this post if it is better, or update with the replacement dynamo.

 

[85Hokie]

Well, whatever winter Louisiana had has come and gone. LOL

But, I removed the battery again before its warranty ran out and had Oreilly "test" it. Still shows to be a good battery.

That said, I did the repeat tests on the voltage and found intermittent drops of voltage. I was about to order another dynamo. When I removed the dynamo from its location, I noticed a bit of dust that shook out of the housing inside. Since I was going to order another one, I decided to open this one up and see what gives. It is a two wire dynamo.

Long story short (and I still may have to replace it) is that I found enough caked dust inside that I hardly could recognize the parts within. I cleaned all the dust out and shined the surfaces including the steel rotating surfaces to a bright finish. Put the thing back together. It felt different with the magnets seeming to be in more resistance when turned by hand.

So, warm weather is here and I am about to find out if I did any good. I will update this post if it is better, or update with the replacement dynamo.

DONT quit on your old dyno just yet! When you place in back on, after that good ol cleaning - check those two leads for AC voltage.

I took my dyno - placed the mounting flange in a vise - rigged up my drill to turn the pulley at a good rate - and checked to see IF I had any AC voltage- If I recall - it was something in the 20-30 volts.

Try that before ordering a new one....

 

[lugbolt]

Dynamo's are dirt simple. They rarely fail, and usually when they do, it's just seized bearings. New bearings and they're back to working again. Cheap and easy. They just aren't as efficient as an alternator, and they don't charge as many amps.

I've had a few of these (ZD25's and ZD28's) in recently for same issue. One had a bad combination box. Another had a bad regulator. Another had a broken wire between the regulator and the dynamo-and that one was tough to find. Another had some corrosion in the harness connectors. So based on what I'm seeing out of these, you may have your work cut out for you trying to find it if you haven't already.

 

[Tooljunkie]

Something else to ponder, if mower uses electric clutch it may be drawing more than dynamo is putting out. Get a voltmeter on your dash, it will indicate more than anything else. Battery voltage, starting voltage running voltage and voltage drop when accessories turned on. All relevent and simplify diagnosis.

 

[sagor]

Somewhere along the way, the dynamo has to feed a rectifier assembly. If one of the diodes in that assembly has shorted out (though they usually fail open circuit), that short would drain the battery back through the dynamo.
Check any resistance from the battery cables back to the dynamo, to make sure there is no current leakage back to it. Or, if you check the dynamo outputs when parked (turned off), there should be no voltages showing (to ground) if the rectifier is good.

 

[lugbolt]

Found another issue today with a ZD25. The 2 wires that come from the dynamo run over to the reg/rectifier assembly, through a harness with other wires-one of which turns the regulator on and another which is the charge wire, (white IIRC) that runs from the reg/rect to the starter. That wire has a 3 way connection inside the taped harness kinda down under the radiator, right side, where it makes the turn from going across underneath the radiator up to the reg/rect. One of the wires was partially broken off in that 3 way connection, corrosion. Had to partially remove the harness, cut it open, and repair that connection by soldering and shrink tubing, then re-taping it. I prefer not to use regular tape as oils and heat will cause the glue to loosen. I use silicone "tape". Much better quality and not affected by oils and heat up to about 500 degrees. No adhesive either, so it's pretty easy to wrap it. It only sticks to itself. Tesa makes some, order it online. I get it locally-different brand though-but more or less the exact same stuff.

 

[JimDD]

Still not finding drain of battery. Bought a new battery just to take that out of the picture. Still happening with a new battery.

I began some wire testing on the circuitry to see if I could find a wire that may be leaking to ground.

The regulator is brand new. I tested the continuity from the dynamo which is also new, on both wires to the plug at the regulator and all that checks good.

I also checked for continuity on the wires in the charging system fuse line. That also checks good.

I am unsure of where to go next with diagnostics, but I fear that there may be a hard to diagnose issue with the mower's combination box. Does anyone have some guidance on how to begin to check this component out and what kind of meter readings should I look for? I see no way described in my Shop Manual of how to check the combo box. I also see no explanation of how to test the stop solenoid.

Any help would be very much appreciated.

To recap this thread, I charge the battery before each mowing and the mower keeps running fine for the period I cut. But, the instant I stop the mower for refuel or something else, the mower will not restart and the battery is always found at about 75% of charge. I charge back up to 95-100% and mower starts up fine.

 

[85Hokie]

Still not finding drain of battery. Bought a new battery just to take that out of the picture. Still happening with a new battery.

I began some wire testing on the circuitry to see if I could find a wire that may be leaking to ground.

The regulator is brand new. I tested the continuity from the dynamo which is also new, on both wires to the plug at the regulator and all that checks good.

I also checked for continuity on the wires in the charging system fuse line. That also checks good.

I am unsure of where to go next with diagnostics, but I fear that there may be a hard to diagnose issue with the mower's combination box. Does anyone have some guidance on how to begin to check this component out and what kind of meter readings should I look for? I see no way described in my Shop Manual of how to check the combo box. I also see no explanation of how to test the stop solenoid.

Any help would be very much appreciated.

To recap this thread, I charge the battery before each mowing and the mower keeps running fine for the period I cut. But, the instant I stop the mower for refuel or something else, the mower will not restart and the battery is always found at about 75% of charge. I charge back up to 95-100% and mower starts up fine.

OK - here is another way to skin this cat,
unhook your neg cable on battery, take your VOM and set it to AMPS - NOT VOLTS!!!! , (gonna have to use the other hole on the meter typically) take one lead and place it on the unhooked battery lead, take the other and place it on the battery terminal that has no lead.........

- if there is indeed a battery drain, it will show either a pos or neg number .....this is all done with the engine off.

Tell me what the amp draw is - I gonna guess something high, like a couple of amps......

now if you can - unplug fuses, pull out fuse and "see" if amp draw changes.....replace fuse, keep doing this until you find something that makes it go to zero.

If none of the fuses are telling the story, then you might need to unhook the leads to the rectifier/regulator and go from there,

something is killing the battery - did you ever tell us what the charging circuit is placing on the battery at near WOT? Again, the dyno is not gonna place a lot of juice at idle or even at 25% throttle, but once you run up the rpm range, you should be getting 14+ volts DC at the battery.

Report back any and all findings.

 

[lugbolt]

To recap this thread, I charge the battery before each mowing and the mower keeps running fine for the period I cut. But, the instant I stop the mower for refuel or something else, the mower will not restart and the battery is always found at about 75% of charge. I charge back up to 95-100% and mower starts up fine.

If this is what's happening, you likely don't have a drain. You likely have a charging system issue. Drain and no-charge are two different animals!

What is your battery voltage with the engine running full throttle? Use your digital volt meter.

To recap. The mower uses a little juice to make the electrical components work. So while the engine's running, you're using juice. But is the dynamo replenishing the juice at a rate that would keep the battery charged? It doesn't sound like it. What is your charging voltage? 12.82v? 29.3V? Need to know this before spending any more time on it.

 

[100 td]

An extension to what's been said, you have checked the fuse in the charging circuit?
Check for 30V+ AC at the regulator on the dynamo leads.

 

[Tooljunkie]

Machine starts with full charge only.
Machine will run all day and not restarting without recharging battery.
So,tractor wont start hot?
Battery not getting recharged by electrical system?
Dynamo putting out less power than running mower/tractor demand?

Speculating and throwing parts at it isnt the correct approach.
Measure-
Battery voltage before starting and after starting. Running voltage Must be no less than 1 volt ABOVE battery voltage than before starting.

 

[JimDD]

Found another issue today with a ZD25. The 2 wires that come from the dynamo run over to the reg/rectifier assembly, through a harness with other wires-one of which turns the regulator on and another which is the charge wire, (white IIRC) that runs from the reg/rect to the starter. That wire has a 3 way connection inside the taped harness kinda down under the radiator, right side, where it makes the turn from going across underneath the radiator up to the reg/rect. One of the wires was partially broken off in that 3 way connection, corrosion. Had to partially remove the harness, cut it open, and repair that connection by soldering and shrink tubing, then re-taping it. I prefer not to use regular tape as oils and heat will cause the glue to loosen. I use silicone "tape". Much better quality and not affected by oils and heat up to about 500 degrees. No adhesive either, so it's pretty easy to wrap it. It only sticks to itself. Tesa makes some, order it online. I get it locally-different brand though-but more or less the exact same stuff.

I peeled back the wiring cover for this area. I did see a white wire there, but my Regulator has no white wire, confirmed by the WSM. I also see no white wire at the starter. Where am I confusing this point you made to find a possible three way connector that is corroded? Thanks for your help, Lugbolt!