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Briggs and Stratton tractor motor not charging battery

This is a discussion on Briggs and Stratton tractor motor not charging battery within the Small Engines forums, part of the Tech Support Forum category. So I've been trying to track down a non charging battery on my parents old lawn tractor. The engine is:


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Old 07-06-2010, 07:07 PM   #1
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So I've been trying to track down a non charging battery on my parents old lawn tractor. The engine is:
Briggs and Stratton
Model: 28N707
Type: 0666-A1
Code: 970203ZE

When running the battery shows no charging, just a steady decline from 12.4v. While in a rush I ordered a Voltage reg. for that model since in my limited experience that was a common fault. WRONG. Unless there has been a serious hack job in the wiring sys. by the previous owner, This model engine does not have a voltage reg ( FYI part # 794360 ).

i'm having a difficult time with it since I have zero manuals, no wiring diagram and what seems to be an accurate parts breakdown, but since it showed it actually had a Voltage Reg, but didn't..I'm not sure how accurate it is.

I have 2 questions:
1: How do I test the stator/alternator? (this is the description the book shows me, I assume that's the only area left to check) Can I test the Diode on I think the red wire?

2: Assuming it's bad, which one do I need? This is what I'm reading from:
http://www.partstree.com/parts/?lc=b...A1&dn=01480009
Mine has the square white connector with red and black wires coming from the stator to the connector. I assume this is the 'Dual Circuit'?

Thanks for any help.

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Old 07-08-2010, 11:15 AM   #2
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with the tractor running put a meter across the battery to see if it putting current back to the battery, the diode can also be tested with a ohm meter. the diode is directional meaning current can only flow in one direction. the alternator windings are under the flywheel, and if you don't have a flywheel puller you could be out of luck.

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Old 07-11-2010, 10:08 AM   #3
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Checked the Stator for voltage (red wire). I can't seem to get a good reading before the diode, but after the diode I only get 8v max. The battery itself is 12.7v, meaning it's not getting a charge.
I'm having another wonderful issue, which is getting in the way of trouble shooting the non charging issue. When I was checking over the machine for any electrical faults, fuses, etc. I noticed the oil was full of gas. This was most likely from the float needle being stuck open a bit. I removed the carb, cleaned it up, blew out all the passages with low pressure compressed air and made sure the float was leak free and the passages weren't blocked. I also removed the old fuel filter and replaced it with a new one. When putting everything back together I noticed the air gap was incorrect for the coil and returned it to the .010" recommendation. I changed the oil and buttoned everything up. Upon starting it up, it has little power and is running very lean. So much so the exhaust pipe gets red hot. I adjusted the idle mix a bit with no discernible affect. I changed the fuel filter back to the original B&S one just in case that was the lean fuel issue, but it was the same.

What else did i do to make it run lean?
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Old 07-11-2010, 10:09 PM   #4
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If you are checking the current before it reaches the diode, your voltmeter must be set to AC volts. You should be reading about 28 v AC. Dependant on whether you have a electronic PTO or manual PTO, you should read 3 amps DC with a manual PTO or 5 amps DC with an electric pto after the diode. Normally the dual circuits are capable of 9 or 10 amps. The voltage after the diode should read 14-16 volts DC and depending on the state of charge of the battery, voltage will vary. for instance, as long as you are seeing an increase in voltage with the engine running full speed vs turned off your probably OK. example; check voltage before staring engine and it reads 11.8 V DC. Start the engine and bring to full speed and check voltage at the battery and it should read around 12.5 with a slow increase as the three amps charges the battery and since it is unregulated, may reach as high as 15 v DC. Your light circuit AC amps should be between 5 and 6 amps however it is hard to get an accurate reading and as long as the headlights are bright at full throttle all is OK. in summary, when checking AC voltage at the plug you should get around 30 v AC at full throttle. after plugging in and checking after the diode, it should be around 14-16 volts and 3-5 amps 12 v DC.

Now for your lean condition. the "normal" fuel air ratio for an engine to run properly is about 15 to 1 on these small engines. A lean mixture will be caused by; an air leak between the venturi and the intake port...make sure gaskets are in good condition at the carb/cylinder head joint and that the bolts are good and snug; a plugged high speed circuit in the carburetor. The cause is either a malfunctioning shut off solenoid at the bottom of the bowl or dirt/sludge in the jet or orifice passage. Remove the bowl and ensure the rubber o-ring at the main jet is in good condition, remove the main jet and ensure it is clean, spray carb cleaner through orifice of the main circuit passage and ensure the fluid flows freely into the venturi area of the carburetor.

Now the ignition circuit, you state that you are getting a spark but are not sure if it is strong enough. The spark should be a bright blue and if so, your most likely fine. Ensure the gap is correct at the magneto (.008-.012) and that the flywheel key is not sheared.

Let us know how you make out.
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Old 07-13-2010, 04:03 PM   #5
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As you can see the key was already sheared enough to fall apart in two pieces when the flywheel came off. I made a new key, flicked it on and it purred like a kitten.

Now that I can properly troubleshoot the charging system at the right rpms, The stator is putting out almost 17v I finally found a wiring diagram so I can either:

A: Hopefully find the short that's not letting that 17v get to the battery.
B: on the advice of a B&S tech, bypass all the wiring between the connector after the diode and the battery by making a new fused wire directly to the battery.
UPDATE:
Making some progress, However After trying in vain to find the wiring issue, I just made a new wire from the red wire from the stator, after the connector directly to the pos. terminal on the battery as indicated. Unfortunately I keep blowing fuses before the stator end of the wire is even attached to the connector> new wire> Battery. Obviously it's 'shorting' through the old wiring, which is kind of why I was reluctant to try this initially. If this is indeed a good solution (wiring on the tractor is a nightmare) what fuse should I be using? I initially tried a 4 amp 250v fuse, then a higher amp fuse whose value I've forgotten at the moment. Both popped when I hooked everything up.

As for troubleshooting the wiring issue, I just checked that with the key on, I had continuity from the stator, through the key switch, ammeter, 30 amp fuse, solenoid and pos. terminal of the battery. I guess I should be testing the voltage as it's running, but that's a little difficult to test these points without disturbing the engine running.
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Old 07-13-2010, 04:50 PM   #6
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Just a side comment... I hope you did not make the new key out of steel.

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Old 07-14-2010, 07:26 PM   #7
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I did, but later learned that B&S have a special shearable key. I'll replace it before I'm done with it. Thanks though!
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Old 07-15-2010, 05:34 PM   #8
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Aluminum key that is. $1.40 well spent
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Old 07-15-2010, 09:05 PM   #9
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what gauge wire are you using should be 10 or 12 The fuse should 20 or 30 amp .... a 4 amp fuse is not strong enough
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Old 07-17-2010, 04:31 AM   #10
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Did you bypass the diode? The diode MUST be in line to convert AC to DC current. So the wire direct to battery will work fine but you must splice in after the diode. You need a 15 amp fuse...maybe 20 if the 15 blows...if the 20 blows you have a short somewhere.
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Old 07-20-2010, 04:28 PM   #11
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Yay frustration.

So been a busy few days but I tried to finish this piece of sh-- tonight. I swapped in the proper B&S aluminum key and started it up, nothing. After trying a few things, I took the flywheel off and found the key sheared again. What the hell? The motor spins freely, nothing is touching the pulley underneath etc. I popped back in the steel key and it runs perfectly.

Aside from that problem, I thought I'd at least square away the charging issue and focus on 1 problem. I figure the wiring from the tractor side of the stator connector has a short (for all my looking and testing..I can't find it) this is the initial charging issue + causing the too low fuse to blow. As a test I re-checked the output after the diode on the stator and found the Voltage ranges from 8v at idle to almost 24v at full throttle. I have a wire from AFTER the diode and white connector directly to the battery w' a 30amp fuse. I cut the red wire that would go through the ammeter, key switch etc..and re-attached the connector (red wire going directly to the battery, white wire going where ever the hell it goes). At high throttle, the battery is STILL only at 12.7v. I even cut the white wire after the connector, same thing. I have continuity through the connector, but nothing above 12.7 at the battery no matter what the connection I try. I don't want to hack apart the stator connector end if I can help it.


And please don't worry that I'm just cutting wires all willy nilly, It may sound rough, but they'll be soldered back properly :)

Hope that made sense. Thanks for any help!!!!

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