D722 not charging. VR output low

[lugbolt]

do a voltage drop test on all wiring. If you did aircraft electrical stuff, you know how to do that. This assumes of course that you've not already done it.

20v is low. Remember a VR is also a rectifier, and a rectifier cuts the ac voltage basically in half, so I like to see 30v+ out of dynamo's (no load full throttle). On my mom's g1800, just got through playing with the electrical system on it and the dynamo puts out around 60VAC at maximum rpm (3600 engine rpm, and remembering that the crank pulley is larger than the dynamo pulley meaning the dynamo turns more rpm than the crankshaft). Also remember, the dynamo output is AC voltage (I think you know that already) and if you test it on DC meter setting it will show "off".

if it were mine (and it's not) I'd put a small Kubota alternator on it and make the wiring changes & be done with it. Those little alternators are like $40 or something on scamazon. You'll also need the spacer, get it from a bx1800 or similar, same for the little alternator. Nothign wrong with the dynamo, they're just weak as far as amperage output and the regulators aren't set up to charge all that well either. I like to see 14v-14.5v and most of the kubota dynamo'regulators will only do 13.5-13.8. It works but it's not ideal. In the case of my mom's little mower, 14A is plenty. It doesn't have much of an electrical draw while running. The lift pump and hourmeter but that's about it.

oh, one last thought. I had a ZD326 show up once wasn't charging very well. Someone had the dynamo apart to put bearings in it (simple task) but didn't get the nut that holds the pulley to the shaft tight enough and it was slipping. That was interesting to find.

 

[GreensvilleJay]

yucky outside. so looking at this more..

REGULATOR-VOLTAGE - KB-RP201-53710 | Troy-Bilt Canada

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bit of a sticker shock !!!! Best price is $30+-.

Wiring looks similar to the unit in ZD-21-28.pdf.(from kubotabooks.com)
If so it consists of 2 parts, a full wave bridge for actual battery charging and a section with 2 PNP transistors ,and 2 resistors to control the 'charge ' light.
So if the guts are as posted, there is NO 'regulation' form the unit, rather the battery conditions dictates the charge rate. 20 VAC becomes 28 VDC ,so more than enough.

 

[mrburt]

yeesh, you can get them off amazon, next day....
checked ,the dynamo's rated for 14 amps, the the rect/reglator is 6 pins, black MUST go to good ground.
I'll have a look see if I can find an actual schematic of what's inside the 'regulator'
20 volts going in is good,

I'm supposed to get freezing rain at 3AM tonight.....probably get the 'leftovers from you , thanks !

OK, grabbed and turned your diagram and 'they' show pin 2 of the regulator going to a 'ring' terminal that is screwed into the 'frame'. If possible run a wire (16ga+-) from there to the battery -ve.

If there isn't a GOOD ground, reg will not operate properly.

I checked with a meter, replaced the wire and grounded the VR case. Nothing seemed to matter.

 

[mrburt]

This morning I checked the dyno output at idle and full rpm, no load and hooked to VR. Load or no load volts were the same this time. 13.2 vac no load to 30 vac w/load. Now this is with the warranty replacement VR. Not sure why last time with a load was 20v at max rpm with load but this is first time for this test with the warranty VR. Intermittent connection possibly.
Still not charging.

 

[mrburt]

And FYI. Since the wiring diagram for the unit is top secret I took the base Kubota diagram and made as many changes to match the equip. But w/o a diagram I can't correct all.

 

[GreensvilleJay]

Assuming the 'VR is same as this one, there are 4 diodes in a bridge( diamond pattern) that convert AC from the dynamo into pulsating DC to charge the battery. there is NO 'regulator'. The 2 diode,resistors and transistors are used to control the 'charge' light .

 

[mrburt]

More tests.
Dynamo reads the same 13/30VAC idle/full with all three VRs .
Battery at 12.9V before starting.
After start 12.4 while running with any VR and with engine shut down but key on with any VRs
With key off batt voltage climbs slightly to 12.7.

 

[GreensvilleJay]

If there's a fuse between the VR and battery , replace it with ammeter(+-10 15 amps), see what it says.

 

[mrburt]

do a voltage drop test on all wiring. If you did aircraft electrical stuff, you know how to do that. This assumes of course that you've not already done it.

20v is low. Remember a VR is also a rectifier, and a rectifier cuts the ac voltage basically in half, so I like to see 30v+ out of dynamo's (no load full throttle). On my mom's g1800, just got through playing with the electrical system on it and the dynamo puts out around 60VAC at maximum rpm (3600 engine rpm, and remembering that the crank pulley is larger than the dynamo pulley meaning the dynamo turns more rpm than the crankshaft). Also remember, the dynamo output is AC voltage (I think you know that already) and if you test it on DC meter setting it will show "off".

if it were mine (and it's not) I'd put a small Kubota alternator on it and make the wiring changes & be done with it. Those little alternators are like $40 or something on scamazon. You'll also need the spacer, get it from a bx1800 or similar, same for the little alternator. Nothign wrong with the dynamo, they're just weak as far as amperage output and the regulators aren't set up to charge all that well either. I like to see 14v-14.5v and most of the kubota dynamo'regulators will only do 13.5-13.8. It works but it's not ideal. In the case of my mom's little mower, 14A is plenty. It doesn't have much of an electrical draw while running. The lift pump and hourmeter but that's about it.

oh, one last thought. I had a ZD326 show up once wasn't charging very well. Someone had the dynamo apart to put bearings in it (simple task) but didn't get the nut that holds the pulley to the shaft tight enough and it was slipping. That was interesting to find.

I know how but not going to on all wiring. Have to rip it entirely apart. I did pull the wire from the vr and with no load it was putting out 11.9 volts. And I did remeasure the dyno - 13.3 idle 30 full rpm. Not sure how I got 20 before but no worries. I hesitate to start throwing parts at it as that can add up and if its not fixed more money down the drain. At present I'm waiting, not very patiently, for a reply from China. They usually send by slow boat.

 

[GreensvilleJay]

curious found this... https://www.temu.com/ca/rs5101-regu...&refer_page_id=10009_1738881667377_uufscqi6rm

'RS5101' is the 'model number' , on amazon here for $60 !

Send me the make/model of the miniexc , I'll surf the web tonight.Seems there's alot of small ones out there with same engine

 

[mrburt]

I'm on my 3rd. No change with any of them.
Thanks anyway.

 

[lugbolt]

i doubt your vr is bad, i doubt 3 of them are bad

it's most likely wiring or ground issues which is why i suggested a voltage drop test. Don't really need to rip the wiring out, just get access to the reg/rec and the source (battery). If there's a big drop, then you can start tracking it down but I like to test each END first

 

[mrburt]

i doubt your vr is bad, i doubt 3 of them are bad

it's most likely wiring or ground issues which is why i suggested a voltage drop test. Don't really need to rip the wiring out, just get access to the reg/rec and the source (battery). If there's a big drop, then you can start tracking it down but I like to test each END first

I agree. Slim chance the VRs are bad. I've checked, cleaned, bonded and tightened the wiring between the VR-Batt-Dyno. I don't have a real schematic so I'd have to physically follow each wire to be sure where it goes. With the VR output unplugged I get 11.9V. Plugged in I get battery voltage. Next step is check current draw on this wire.