[jrs76]

I just "inherited" a 5-7 yr old Troybilt rider with a 17.5 hp B&S that will not charge the battery. I replaced the battery twice as the old one was bad and the one that was bought last year is now bad also. I would like to get this issue figured out instead of replacing batteries every year. After installing the new battery it started fine but after @4 hrs of use the battery is down again. I have checked all the grounds and fuses....can't find any issues. My question is how to correctly check the stator and diode in hopes of getting a good diagnosis. It has an in-line diode just above a two pin connector. What should the dc volts be after the diode at the connector and am I even on the right track?
Any help would be greatly appreciated.

 

[Mark / Ohio]

Welcome to the forum jrs76!

Charging circuit design (amperage output) varies some from one engine model to the other. Briggs has some useful information posted on their website to help you determine which charging system you have and the readings you should get if it is working proper.

http://www4.briggsandstratton.com/miscpdfs/RNT/alternator_id.pdf

http://www.briggsandstratton.com/support/frequently-asked-questions/engine%20charging%20system%20setup/~/media/B20844E4F6F541D1935652922E87B1A3.ashx

Testing the Electrical System | Frequently Asked Questions | Customer Support | Briggs & Stratton

The quick simple test I first make is to check the voltage of the battery with the engine off. Then check it again with the engine running at or near full rpm. In a working charging circuit the voltage should read a little higher with the engine running. Basic rule of thumb I use with engine off 12.4V +/- 1Vdc for a charged battery. Engine running and full rpm approx. 12.7-14.7Vdc

 

[jrs76]

I checked the volts not running....12.5
Started the motor, full throttle....slowly climbed from 12.5 to 16.3....I shut it off when I saw it was still climbing at 16 as this was above your recommended level....so is it over charging and boiling the battery?....and what is the fix if so?
The motor info is as follows:
B&S 17.5 hp I/C OHV
Model 31C707
Type 0603 E1
Code 0511112D

Troybilt mower...."Pony" on the side. 42" deck
Sorry the mower and my computer are at different locals so I dont have the mower model number right now.

Will see if I can get any info on B&S.com

 

[rhenning]

Over charging and killing the battery. On small garden tractor batteries it wouldn't take very long. Roger

 

[Mark / Ohio]

Yeah, that voltage does sound high. My guess would be a bad regulator. Looks like it uses a Briggs #696459 alternator by the parts list I found here:

Customer Support | Briggs & Stratton

Regulator would be Briggs #790292 according to the alternator cross:

http://www4.briggsandstratton.com/miscpdfs/RNT/alternator_id.pdf

You really need to verify though that is the system you have either visually or maybe we can come up with a wiring diagram using the Troy-Bilt model number as a way to cross check and verify it.

 

[jrs76]

OK, the tractor info is:

Troybilt
model 13AN77TG766

From what I can see, this rider/motor combo does not use a regulator. So is the answer just to change out the diode (harness)?

 

[jrs76]

Here is the Manual for the Mower:
PDF Manual Web Archive

 

[rhenning]

T diode only changes the AC voltage in the alternator to DC voltage you can use. It doesn't controll voltage at all. Roger

 

[jrs76]

OK, I'll look over the mower tomorrow and find the regulator....now that I think about it i didn't see any electrical wiring info in the mower diagrams.

 

[Mark / Ohio]

Unfortunately I have not been able to come up with any more specific diagrams. If nothing else maybe give MTD a call or email and see if they will email just that part of the service manual.