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Hi everyone, new to forum. I have a B&S 2011 21hp Professional series in my mower. Battery has been dead for about 2 months, I have to jump start it. I've just started diagnosing the problem. My mower does not have headlights, so I can't do the Briggs battery test by turning headlights on and off. I did however after much searching find the stator connectors. From what I can tell I have a dual circuit connector. See pic below. My mower (Greenfield Australian brand) has one orange wire out of this connector (connected to red) that goes to the ignition switch. I haven't pulled the gas tank so trace the wires back to the battery, but I assume this does lead back to the battery.



Anyway, here's my findings from multimeter testing that have me seriously confused.

1. red probe in end of orange wire to battery and black probe on battery negative terminal. Shows 106 volts. with ignition on or off. When running it jumps to 130 volts. If I just check the battery it shows 12.4V as it should. I though this wire should basically show battery voltage. I have no idea how it shows 100+ volts

2. when probing the stator. Black probe to back wire (AC) and red probe to red wire (DC) MM on AC setting it shows 20 volts. This is lower than I was expecting. Should I be probing both, or just probe the DC out with red and ground the black probe?

My main question however is the 106 volts test above, that seems really weird, and I maybe doing something wrong.

Advice welcome. I know it could be that the 9 year old battery (140 hours run time) has just finally died, but before I long $130 down on a new battery I at least want to make sure the charging system is working as it should.

Thanks in advance

Congratulation on your purchase of mowers
Your numbers are meaningless and obviously wrong
I would guess you are using an auto ranging multimeter and what you are seeing is millivolts or microvolts
Set it to Ω and test the red wire at the plug and about 1" back from the plug.
There should be a diode in the plug that chops up the AC into pulsed DC to charge the battery
So with the Ω setting you should see 0 in one direction and "overload / out of range" when you swap the probes around .
Start the mower with the white plug undone
You should see something higher than battery voltage with the engine at full speed
If it is lower then 12 V DC then time for a new stator

If the diode fails it can be replaced depending upon your soldering skills

Thanks I got my stator test wrong. I have re-tested that.

Engine running

1. red probe in red wired with diode, black probe to battery ground. 4.4 amps tested which is exactly where it should be
2. Red probe to black AC output and black probe to battery ground 14V AC (as it should be)

so stator seems to be working fine.

But when I still probe the orange wire that goes from red wire / diode out of the stator ...the orange wire should go to battery. It still show weird voltage. This time 154 Volts after I shut down the engine.

Only literature I can find that show a silly high voltage reading is when battery has dropped a cell or two that might show crazy high voltage numbers.

I'm guessing battery is toast

The RED wire from the stator goes through the diode and connect=s to the battery to recharge it
The black wire goes through the white plug then into the white wire to the engine plug and there is nothing connected to it so don't worry about it .
I have no ida what it is reading unless as peviously mentioned it is millivolts which would be leakage across the plug from the battery wire
Saturate the engine to mower plug with WD 40 or similar , plug it in & out a dozen or so times then blow it out with compressed air ( if you have it )

If the red wire shows 3A or better going back to the battery you are fine.
What is very important is you fit a sealed pressure valve regulated battery and not a cheap flooded cell battery
Even better is an AGM PVR sealed battery
This diode system pumps put pulses from 0 V to 14V then back to 0 again. followed by nothing ( because it chops out the negative side of the wave ) then the 0-14-0 pulse again
This is very bad for the battery as it becomes the regulator and gets really hot boiling off the electrolyte and shortening the battery life.
Depengine upon which model you have you also get acid splash all over the aluminium pulleys.

Thanks will do...

here should be a wiring diagram in he back of the owners manual.
They used o be available on line but no sure now that Cox have taken over Greenfields
Which model do you have ?
Got a couple of customers still running 8-24's with the old steel pan seats.
Buggers to mow with cause you slide back & forth on the highly polished pan as you change directions

I have a 2011 32 Fastcut. But it seems to have an orphan B&S 21Hp engine which not many have 33M777 0124 B1 model engine. I'm convinced now the battery is stuffed. Going to buy a new one tomorrow

Before you do, what type of PTO has it got ?
manual or electric ?
The electric blade clutch draws 2.5 A so the 3A stator is never going to keep up.
The Fastcut singles started with 11Hp 25 series engines and ended with 24Hp 33 series so it could be an original engine .
Greenfields did not go overboard with specification as they would change them a dozen times in a season
Add to that they silly with engine choices so you could get almost any engine, despite the OM only listing B & S you could also get Honds, or Kawasakis.
Only know this as I have a lot of one owner mowers with "non standard" engines.

Manual PTO. Definitely an original engine. My only issue now is why am I getting 100+ volts testing the wire that goes back to the battery. It makes no sense at all. Going to try a different MM (mine's auto)

FWIW and i ain't much, this is what Greenfields call a wiring diagram for your mower .


As I was trying to tell you, only 1 wire from the stator is connected, the red wire, which changes colour to orange at the engine plug then goes to the key switch and from the key switch back to the solenoid via the red wire then back to the battery via the main power cable
Note there is a capicitor wired in parallel with the battery to power the hour meter when the mower is turned off.
If you are measuring the Orange to ground with the engine off then you are measuring the charge on the capicitor .
I am fairly sure that you should get a 0 V reading on that wire when the key is off as there is a clamping diode on the Orange wire
Does the hour meter work ?

To be honest I have never measured the voltage there, key off because there is no point in doing it
Just battery voltage engine off and battery voltage engine on
I also check for AC at the battery engine running which shows the stator diode has failed closed circuit.
The battery voltage engine running should be higher than engine not running.
On these systems I like to jump start from a flat battery then take an Amp reading on the red wire using a clamp on meter
If that shows 2A or better then the alternator is OK & I am onto the next mower .

bertsmobile1 said:

To be honest I have never measured the voltage there, key off because there is no point in doing it
Just battery voltage engine off and battery voltage engine on
I also check for AC at the battery engine running which shows the stator diode has failed open circuit.

Click to expand...

Sorry if the diode should fail as open circuit there will be no voltage either AC or pulsed DC to be outputted from the stator. Only a shorted diode will output AC only with no pulsing DC.

When diode is working correctly it rectifies the AC into a half DC pulse voltage which the battery which acts as a large capacitor smooths out into near pure DC and very small AC ripple voltage. Actually most meters only reads average voltage and peak voltage; therefore, the average DC voltage out of this half wave rectifier setup is only = AC reading x .707 when the battery is not present. This because the output is going from 0 to peak and back 0 at 30 times a second (3600 rpm) or less depending on the rpm. Once the battery is added and it charges then the meter reading be higher as it will not read less than the battery voltage. Current to the battery will drop to zero whenever the output voltage from the stator drops below the battery voltage.

This like saying a wire has a short in it when wiggled causing the voltage drop outs when in fact it is open circuit occurring during the wiggle test.

Yep hour meter works

Thank you Star
My typo has been corrected