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I have a Troy Bilt LT-2146 with a Briggs Intek 21hp twin (Model 407777). The battery is not charging - it is not receiving a charging voltage, even at full throttle. I checked all fuses and then suspected the voltage regulator was bad, as it is a common problem. I looked at numerous videos about testing the regulator, BUT, I looked and looked all over the engine (including taking the shroud off) and I can't find anything that looks like a voltage regulator! In all the videos, it is usually bolted on the side of most Briggs engines and quite accessible. I did locate a wiring harness and probed it and found a 35VAC output, so looks like the stator/alternator is working. However, I could never find a wire with a DC voltage above the battery's resting voltage (with the engine running full throttle), so I do suspect a bad regulator. There are some wires wires from this harness (next to oil dipstick tube on right rear of engine) that appear to go up under the flywheel. On this particular engine, is it possible the voltage regulator is on top of the engine under the flywheel? Like I said, I've looked over the entire engine and can't find it elsewhere - seems incredible one would have to pull the flywheel to change the voltage regulator!

Where the heck is that regulator???

The voltage regulator will not be located under the shroud. This manual should help you identify the type of charging system you have and how to test it. Look at the color of the wires and connectors. When testing you must have a fully charged battery and need 12V going to the regulator which if your engine has one will be on the the outside of the engine. If your have a diode system testing is different. https://docs.google.com/open?id=0B6NaqjIxWV1ySkZjTTA5TGltZEE

How about posting the complete model number with type and code so we can see exactly which engine that you have.

Rivets said:

The voltage regulator will not be located under the shroud. This manual should help you identify the type of charging system you have and how to test it. Look at the color of the wires and connectors. When testing you must have a fully charged battery and need 12V going to the regulator which if your engine has one will be on the the outside of the engine. If your have a diode system testing is different. https://docs.google.com/open?id=0B6NaqjIxWV1ySkZjTTA5TGltZEE

Click to expand...

The engine is Model 40777 Type 0229 E1 Code 021018YG.

Well, one problem is solved! According to the manual (THANKS for the link!), I have a "Dual Circuit" alternator and it is unregulated, so no voltage regulator and I can quit looking! Haha!

I followed the dual circuit diode testing procedure on the DC output side (indicated by red wire and raised rib on the white connector) and my meter gave a single beep and displayed a 0.5V voltage drop. As I understand it, this is supposed to mean the diode is good. HOWEVER, I checked for DC output voltage (by connecting one lead of meter to DC output connector and one to ground) and it indicated 24V AC at full throttle, not DC!!! (on the AC/lighting circuit output, it showed about 14VAC).

My questions are:

Is the diode and or stator defective despite the diode test results?

If just the diode is bad, the manual mentions a "service diode replacement harness," but I can't find an exact description for the part in the parts manual.

Or, does one have to replace the entire alternator/stator?

So the diode test shows continuity in one direction but infinity if you reverse the leads correct. Also something to check is to make sure you are getting battery voltage on the tractor side to that connector with the diode on the engine side.

back test the red wire on the mower side of the plug to ground.
It should be at least 14V.
Then follow this wire back.
A lot of switches ground that wire when the engine is turned off to turn the alternator into a bad electric motor so it acts as a brake.
These wires oft burn out at the connections.

Having determined that my dual-circuit alternator's diode was bad (no DC charging voltage), I removed the original diode and plug and replaced it with a Briggs #393456 Alternator Connector Wire (which includes the diode and plug) and now have DC output.

From the mating plug of the alternator connector, I never could establish continuity all the way back to the battery with the key either on or off. As the wire is buried in a loom bundle and near-impossible to completely inspect, I ran a new wire all the way back to the battery and connected it on the same solenoid terminal as the + battery cable. The battery now charges when the engine is running!

Questions:

Does the +DC output wire from the alternator's diode need to have a switch between the alternator diode and battery, or can it be left just direct wired to the +12v side of the battery? I didn't know if there would be any leak back of battery charge through this connection to the alternator when the engine is not running?

Should the charging wire be fused and if so, how many amps? (I used a #12 wire from the alternator connector to the battery solenoid). I noted a 20A fuse adjacent to the solenoid - not sure what it protects and I didn't look closely, but I "think" it is on a ground wire?

Not fuses and can be direct wired to the battery without draining the battery The diode stops any backflow of power from the battery.

The dual circuit diode side is only 3 amp with 5 amp for AC lighting