# 24 HP Briggs not charging



## powertweak (Oct 31, 2005)

I recently replaced old battery with a new one on my Scag mower. Soon afterwards my wife was cutting and blades stopped turning. I found the PTO switch was bad and replaced it. Next time cutting the engine died and the battery was very low. I charged the battery, then load tested it and it checked out OK. I then checked stator output and had questionable regulator output so I replaced the regulator. Full throttle was only showing about 12.5 VDC at the battery. Kept an eye on the battery and it seem to maintain, but then the PTO switch failed again. This time you could see where the heat melted the molded plastic that must have been supporting the contacts for the blade engagement circuit. I pulled my electric clutch, nothing looks wrong with it, 0.4 ohms through the unit and not reading grounded. Air gap about 0.022. The stator puts out 17 VAC at idle and 35 VAC at full throttle. I bought another voltage regulator, this time a briggs 845907. Still not charging to battery. I think the charging system output directly supports the electric clutch and low voltage condition burned the PTO switch with high current. What am I missing? I have checked all wires and connections and grounds, but I have obviously missed something. Any help is appreciated.
B&S 24 HP ELS V Twin Model: 446677
B&S Type: 0127B1
B&S Code: 051003YG


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## 30yearTech (Sep 14, 2006)

The problem is most likely the electric PTO clutch. That's a fairly heavy duty PTO switch, but they can't handle an excessive load without failure. The clutch is probably pulling too much load when it gets hot. 

Typical air gap should be around .010" on an adjustable clutch. Alternator output should be enough to maintain battery with clutch engaged, but does not directly operate clutch. The clutch will operate so long as the battery voltage supports operation.


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## powertweak (Oct 31, 2005)

I will remember that about the 0.010 gap. I still need to figure out why the charging system is not supplying an output at the battery. With the stator putting out 35 VAC at full throttle, but nothing from the regulator red wire, I must have missed something very obvious. I checked continuity between the regulator housing and frame ground and have it. I have read some posts where the regulator housing was not grounded and wanted to make sure I did not have that issue. Thanks for the tip on the clutch.


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## 30yearTech (Sep 14, 2006)

Are you checking for output with the red wire disconnected? This system requires battery voltage to work.

"When testing regulator-rectifier for amperage output, a 12
volt battery with a minimum charge of 5 volts is required.
There will be no charging output if battery voltage is below
5 volts."


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## powertweak (Oct 31, 2005)

I should back up. I tested the stator by unplugging the 2 black stator wires from the regulator and connected my multimeter to the 2 black stator wires and got 35 VAC at full throttle. With the stator wires connected to the 2 yellow regulator wires and the red regulator wire unplugged, I use the multimeter to check for DC volts from the regulator red wire to ground and have nothing. In addition, I reconnect the regulator red wire to the wiring harness and checked for charging system output at full throttle on the battery terminals using a battery tester that had load test option. I of course do not load test with the engine running or battery connected. Did you mean the red wire to the battery or the red wire from the regulator? And while performing these tests I had charged the almost new battery and confirmed it had about 12.5 volts.


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## 30yearTech (Sep 14, 2006)

powertweak said:


> I should back up. I tested the stator by unplugging the 2 black stator wires from the regulator and connected my multimeter to the 2 black stator wires and got 35 VAC at full throttle. With the stator wires connected to the 2 yellow regulator wires and the red regulator wire unplugged, I use the multimeter to check for DC volts from the regulator red wire to ground and have nothing. In addition, I reconnect the regulator red wire to the wiring harness and checked for charging system output at full throttle on the battery terminals using a battery tester that had load test option. I of course do not load test with the engine running or battery connected. Did you mean the red wire to the battery or the red wire from the regulator? And while performing these tests I had charged the almost new battery and confirmed it had about 12.5 volts.


I meant the red wire from the voltage regulator needs to be plugged in. With a fully charged battery, you may not notice much output as the regulator tapers the charge output so as to not overcharge the battery. Leave the battery tester connected and watch it for several minutes, if the alternator is working it should slowly increase output to read around 13 + volts. If the clutch is working normally, you could also engage the clutch and the test meter should show recovery of the battery shortly after the clutch was engaged (assuming the clutch is not pulling excessive load).


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## paulr44 (Oct 14, 2008)

Ensure you have battery voltage at the regulator with the key in the run position. If the regulator can't see the battery, it can't charge it.


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## light mechanic (Jul 18, 2008)

I have several Scags that what the do when the clutch is going out, did it on two of mine melt down of the PTO switch after it burnt the fuse


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## powertweak (Oct 31, 2005)

The grass stopped growing so I have not finished the repairs yet. I took my clutch off and took it to the parts place I use and compared it to a new one; compared how hard it is to turn. Even the new one does not "free wheel", but definitely smoother than mine so I bought the new one. I suspect the additional load of my old clutch burned the PTO switches, but strange it did not blow the 20 amp fuse neither time. I am thinking of putting in a 15 amp to maybe save the switch next time. My Scag only has about 300 hours on it. That clutch is pricey. I am still not sure if my charging system is working. When I previously described the outputs, I broke it down; output form stator, and no output from regulator, but I am not sure if the charging system puts out when the battery is fully charged.


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## paulr44 (Oct 14, 2008)

I have told many students, and have to keep this in mind myself. All the power in the world means nothing without a path to ground. Melted fuse holders or PTO switches usually means a corroded connection somewhere. We see this with corroded fuses, even when they're weather sealed. My own motorcycle cooked the battery off when the VR had a corroded mounting - it ends up overcharging because the corrosion resistance fools the VR into thinking not enough current is being supplied.

A clutch that's on it's way out can provide an excessive load, and also do damage in a similar fashion. We see this too sometimes.


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## 30yearTech (Sep 14, 2006)

powertweak said:


> The grass stopped growing so I have not finished the repairs yet. I took my clutch off and took it to the parts place I use and compared it to a new one; compared how hard it is to turn. Even the new one does not "free wheel", but definitely smoother than mine so I bought the new one.


These PTO clutches incorporate a brake to stop the blades from turning when disengaged. They will not turn freely, you will feel resistance and they will be hard to turn by hand.



powertweak said:


> I suspect the additional load of my old clutch burned the PTO switches, but strange it did not blow the 20 amp fuse neither time. I am thinking of putting in a 15 amp to maybe save the switch next time. My Scag only has about 300 hours on it. That clutch is pricey. I am still not sure if my charging system is working. When I previously described the outputs, I broke it down; output form stator, and no output from regulator, but I am not sure if the charging system puts out when the battery is fully charged.


The clutch draws a heavy current when first engaged, but once engaged requires minimal current to remain engaged. The PTO switch can handle the heavier load for short periods of time (start up), but a constant heavy draw will result in failure after a short time. A smaller rated fuse may not work or may fail prematurely due to the surge when the blades are first engaged.

To increase clutch life, it is recommended to engage at approx. 1/2 throttle and once engaged, increase to full operating rpm's. This reduces wear on the clutch plate. Wear results in greater air gap clearance over time and this requires more operating current to engage the clutch. Higher current draw can cause clutch coil to overheat and fail. If you reduce to 1/2 throttle prior to disengaging, this will reduce wear to the clutch brake.


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## powertweak (Oct 31, 2005)

I installed the new clutch and cut some grass and leaves. I flipped up the seat after cutting for about a half hour and connected my battery tester to the battery and no charging system output. This is pretty much where I started. The battery is about 3-4 months old. I connected the same battery tester to my truck while running and it showed the charging system putting out. On the mower, the battery tester reads about 12.5 volts at full throttle and after I switch the mower off. Where should I start to give feedback to try and find the problem? Thanks


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## paulr44 (Oct 14, 2008)

Hmm, unusual. The 16 amp stator spec. 30 min. volts at 3600 rpm, so you're good there.
You never responded/commented on my comment about having battery voltage at the regulator with the key in the run position...this is a basic test that must be done in a non-charging situation.

Their regulator output test is rather involved. They suggest using a shunt and test the reg. output using the ammeter function of your VOM. The repair manual is part# 273521.

With decent stator output, a new battery and regulator, I think there's a lack of continuity somewhere in the system.


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## powertweak (Oct 31, 2005)

Paulr44 - you previously said _Ensure you have battery voltage at the regulator with the key in the run position. If the regulator can't see the battery, it can't charge it._ So I check for DC volts between ground and the red regulator wire? Do I unplug the red regulator wire? I will check after I hear back from you. Thanks for helping.

Paul - in the meantime I went out to the shop and confirmed battery voltage from battery ground to the red regulator wire when the key is switched on and of course lose the voltage when the key is switched off. I did not unplug anything, just slipped the probe in from the back side of the connector.


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## paulr44 (Oct 14, 2008)

Please test between regulator body (ground) and red wire. When you test from the battery negative terminal (ground) you're bypassing all in-between the battery and regulator body, which is it's ground. If the reg. isn't grounded properly, it can't work right.

I tried to compare regulators, like-replacement 394890 r/b 797375 r/b 691185 to the one your currently have installed, they don't provide more than general range specs on either and both have the same description.

B&S test procedure:

Testing Regulator-Rectifier − 16 Amp System
To avoid blowing fuse in meter when testing DC output of 16
amp system the DC Shunt, Tool #19468 is required.
The DC Shunt must be installed on the negative (-)
terminal of the battery, Fig. 23. All connections must be
clean and tight for correct amperage readings.
Connect stator wire harness to regulator-rectifier.
1. Install shunt on negative battery terminal.
2. Insert RED test lead into receptacle in meter and
insert into RED terminal on shunt, Fig. 23.
3. Insert BLACK test lead into receptacle in meter
and insert into BLACK terminal on shunt.
4. Rotate selector to position.
BLACK TEST
LEAD
RED TERMINAL
Fig. 23 − Testing Regulator-Rectifier 16 Amp
System With DC Shunt
BLACK
TERMINAL
RED TEST
LEAD
DC SHUNT #19359
5. With the engine running at 3600 RPM, the output
should be:
* 3 − 16 Amps − 16 Amp System
* Depending upon battery voltage. For example, if the
battery voltage was below 11 volts, the output reading
would be 16 amps. If battery voltage is at its maximum, the
amperage will be less.
6. If no or low output is found, be sure that regulator-rectifier
is grounded properly and all connections are clean
and secure. If there is still no or low output, replace the
regulator-rectifier.

If you need it, you can get your wiring schematic from Scag for free (download) here, they're in the owner's manuals.


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## powertweak (Oct 31, 2005)

I understand now I left the regulator out of my previous test. I tested for DC volts between the red wire (still connected) to the regulator body, regulator mounting screws, and have battery voltage when the key is switched on. The regulator is #3 counting the original as #1 and is a B&S from a local parts store based on the B&S engine numbers. I don't have the regulator number itself. #2 was a very cheap unit I ordered online and when I still had no charging decided to buy the real thing. I am somewhat familiar with the shunt tool, but do not have one. I do have the Scag wiring diagram in the manual and have used it to look for problems. I checked each connector by unplugging, looking at the connectors and wires, tugged on each wire, ohmed each wire at the connector. Neither of the 2 fuses never blew. Not sure if I mentioned it before, but in addition to load testing the new battery myself, I took it back to O'Reillys and asked them to load test it...it tested good. I am willing to continue checks if you have more suggestions. 2 items I wonder about because I do not understand what they do is a relay under the switch cover and the sealed unit that manages the safety switches. I did have to replace the starter bendix not long before this problem seemed to begin; again with genuine B&S parts. This was required because trying to start it one day when the old battery was weak, the bendix sort of double clutched or perhaps I re-engaged the start switch too soon. At any rate, the bendix gear was a little chewed, so I got the kit and replaced it. The snap on ring is no fun. Don't have that special snap on tool, but used a 10mm socket if I recall. The starter has been OK since then, but thought I should mention it. That was about the time I replaced the old battery because it was failing and would not hold a charge.


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## 30yearTech (Sep 14, 2006)

The relay and control box are all for the safety interlocks and will not have any effect on the battery charging, neither will the starter or bendix.

I would go back and recheck the alternator output, as I would think it unusual to have several bad voltage regulators in a row.


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## powertweak (Oct 31, 2005)

I know it has been a while since I replied, but had some time today so I rechecked the alternator output. To be clear, I unplugged the 2 black stator wires from the voltage regulator. With my meter set on AC volts, at idle I have 16 VAC and at full throttle I have 35 VAC. I confirmed the output, then plugged the regulator back in to the stator wires. Checked across battery for DC volts. I have about 12.5 volts with engine off, idle and full throttle. Knowing the regulator ground at mount is OK and this is a new B&S 845907 voltage regulator I do not know what to check next.


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## 30yearTech (Sep 14, 2006)

powertweak said:


> I know it has been a while since I replied, but had some time today so I rechecked the alternator output. To be clear, I unplugged the 2 black stator wires from the voltage regulator. With my meter set on AC volts, at idle I have 16 VAC and at full throttle I have 35 VAC. I confirmed the output, then plugged the regulator back in to the stator wires. Checked across battery for DC volts. I have about 12.5 volts with engine off, idle and full throttle. Knowing the regulator ground at mount is OK and this is a new B&S 845907 voltage regulator I do not know what to check next.


You could try running a temporary jumper wire from the voltage regulator output, directly to the positive (+) terminal on the battery and recheck your output when off, idle and full throttle. If it shows charging with the jumper then there is a problem in the line from the regulator back to the battery, could be a fuse or ignition switch connection.

I had a similar issue on an eXmark unit and found a bad connection on the fused line going back to the charging system. I was getting a connection when testing for continuity, but it was not charging the system. This unit had a Kawasaki setup, that is very similar to what Briggs uses.


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## powertweak (Oct 31, 2005)

I will try that one night this week. That will be the red wire from the VR. I sincerely appreciate the help from this forum stepping me through the troubleshooting process.


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## 30yearTech (Sep 14, 2006)

powertweak said:


> That will be the red wire from the VR.


*Correct*


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## powertweak (Oct 31, 2005)

Tonight I ran a jumper from the VR output red wire to the positive side of the battery and it was charging around 14.5 volts at full throttle. I followed the red wire through 3 harness connectors / adapters. The red wire becomes a yellow wire; goes through a 20 amp fuse and to the "A" single terminal on the ignition switch. I checked for continuity from the red at first connector beyond VR to the fuse, each side and good, then to yellow wire where it connects to the single terminal on ignition switch. I have continuity, but the A terminal is frame ground. I don't understand how the VR output wire should run to frame ground. I have the Scag manual, but the electrical schematic does not show everything. The manual for my old Craftsman shows the switch contact positions, but I have not been able to find that for the Scag switch (Scag #48798). Is the A terminal suppose to be frame ground? I wonder if the clutch overload melting 2 clutch switches damaged the ignition switch?


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## powertweak (Oct 31, 2005)

Thought about my findings today and when I got home disconnected the yellow wire from the ignition switch terminal and the wire is not grounded. My switch is not labeled, so I am looking at a Briggs 692318 diagram (supposed to be same as Scag 48798 6 pole) and find I read yellow wire to ground when connected to switch because the terminal 6 it connected to is common to terminal 1 and 6 in off position and 1 is switch case ground. I continued to check for the expected continuity between terminals in the run and start positions and the switch checks good. Since the disconnected yellow wire does not check to ground, I have not found the problem. I know a fault can check good for continuity, but fail under a load. I looked closely at the fuse and fuse holder. I didn't want to destroy the fuse holder by taking it apart. I also did not want to remove the factory wrap from the wiring harness but leaning in that direction. I am missing something.


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## 30yearTech (Sep 14, 2006)

What is the model and serial number of your Scag mower? 

You may simply try unplugging and reconnecting all plugs and fuses, sometimes there is just a bad connection and this process may correct it.


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## powertweak (Oct 31, 2005)

Model STC-48-V-24BS Serial B5003813
I understand what you mean about unplugging and plugging back in. I have done that to all connectors while inspecting them with a good light looking for a problem. After doing your jumper test and seeing the system charge, I really looked hard at the PTO switch connector and ignition switch and the fuses. I have obviously missed something or it would work. On the electrical diagram in the Scag owners manual, I do not see the stator or VR. My mower appears to have an additional adapter harness in addition to what the schematic shows. Some of the harness is visible in one of the pictures I attached to an earlier post. A couple of my harness connectors are brittle, which is why you see them taped up in the picture, but when ohming through them did not see anything to lead me to think any shorting occurred.


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## 30yearTech (Sep 14, 2006)

Scag units are known for their bad plug connectors on the wiring harnesses. The charging system will flow through a fuse, and the ignition switch, but shouldn't run through the PTO switch, and usually will connect to the battery at the starter solenoid (hot) battery cable.


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## 30yearTech (Sep 14, 2006)

*Test Each Connetor*

Here is what I would try.

Hook up your meter and check for charging voltage at the battery. Then jump each connector one at a time while checking to see if the battery shows that it's charging. 

You can use a probe to access each connector from behind the terminal at each plug, and jump them there. 

If you show that the battery is charging when you jump a connection, then that's the connection that's causing your problem. You can even try this at the fuse and ignition switch.

This is about the only suggestion I can come up with, since we now know that the alternator and VR are working.

Good Luck...


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## powertweak (Oct 31, 2005)

30 yr tech - that is a great idea for a method to troubleshooting each connection under load. I hope to do this over the weekend. If I find a damaged connector / pin, do you have a preferred source for 4 pin, 6 pin, etc connector assemblies that are heavy enough and high quality? Thanks for the directions. Hope you have a good weekend.


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## 30yearTech (Sep 14, 2006)

powertweak said:


> 30 yr tech - that is a great idea for a method to troubleshooting each connection under load. I hope to do this over the weekend. If I find a damaged connector / pin, do you have a preferred source for 4 pin, 6 pin, etc connector assemblies that are heavy enough and high quality? Thanks for the directions. Hope you have a good weekend.


When I run across a bad connection on a Scag, I usually just pull out the offending plug and install a single external connector to replace the bad one, and plug it in separately from the plug assembly. I carry individual spade terminals, but have not found a good source of 4 - 8 terminal connectors.

Best of Luck....:thumbsup:


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## powertweak (Oct 31, 2005)

So I did not want to leave without adding I give up. I am not able to always get the same readings; for example, now a wire from the VR output to the positive battery terminal does not give much of a charge. Looks like something is trying to bleed part of it. Not buying another voltage regulator. Found a shop about 30 miles away that appears to be good, so hopefully can borrow a trailer soon and take it in. I was tempted to buy a new wiring harness, switch, VR, everything, but that cost is crazy. I really do appreciate everyone trying to help me; just don't know enough to finish this one.


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## 30yearTech (Sep 14, 2006)

powertweak said:


> So I did not want to leave without adding I give up. I am not able to always get the same readings; for example, now a wire from the VR output to the positive battery terminal does not give much of a charge. Looks like something is trying to bleed part of it. Not buying another voltage regulator. Found a shop about 30 miles away that appears to be good, so hopefully can borrow a trailer soon and take it in. I was tempted to buy a new wiring harness, switch, VR, everything, but that cost is crazy. I really do appreciate everyone trying to help me; just don't know enough to finish this one.


Typically if the battery is fully charged, your not going to show a high charge rate, as the regulator tapers down the charge to the battery. You will usually get a high reading right after you start the engine, but if the battery has a good charge, the reading will drop quickly.


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