A-81 BRIGGS QUESTION

[illinilefttackle 399]

Hello again guys- I've managed to get myself back into what I love to do- fix horses. I still am dealing with diminishing eye sight- but everyone has their own cross to bear. Long ago- I acquired an A-81, pretty much complete-except no engine. I had the engine off my fathers MTD in storage-Briggs 12hp. I have got the engine installed, but have an electrical question-I can't see the schematic well enough to figure it out myself. The wiring harness for the 12hp was only partially useable. And I'm having to use the original A-81 ignition switch. I will add a push button electric start . The main question I have is how to connect the Alternator. The MTD did not have a regulator. It seems that the hot wire goes to the alternator which grounds thru the engine block. But if this is true what regulates the charging? Any help you can give would be great. I'm using only parts I have on hand, not buying anything. Thanks-Al

MTD-MODEL-137-653-000-(1987)-PARTS-LIST.pdf

[gwest_ca-(File Mod) 11,393]

Maybe these charts will help identify what you have

Alternator ID chart

http://www.wheelhorseforum.com/files/file/4165-engine-bs-alternator-id-chartpdf/

Alternator wiring

 

Looks like you have 2 wires coming from the engine from the charging stator.

One goes to the lights only and it is unregulated AC current.

The second one should have a small diode in the wire between the engine and the connector. They are usually covered with tape. The diode simply rectifies the AC current so you end up with DC current to charge the battery. Many are not regulated - the stator just won't put out enough current to need regulation. At least that was the plan but have seen cases where the electric pto needed to be on with no drive belt to use up the extra current to prevent the battery from boiling over.

 

Garry

[illinilefttackle 399]

Thanks Garry- I think I've got it= now to fumble my way thru these wires- Al