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: Rectifier / Regulator Question

07-27-2006, 06:29 AM
Hi have an old wheel horse and it has a Rectifier / Regulator, can someone tell me what it does and how to test it if fails, what the symptoms would be if it does fail?


07-27-2006, 10:49 AM
Not knowing what engine we're talking about it's hard to be specific. In general, alternators produce A.C. power and the rectifier assy changed that to D.C. A Voltage regulator controls the voltage out of the alt so all the things that use electrical power & the battery are seeing the correct voltage. Over voltage can be a killer. Batteries will live a short life and lamps will fail and other equipment may not function correctly of fail.

07-29-2006, 01:57 PM
Here's a link to a series of articles that explain your tractors electrical system in an easy to read form. Go to:

07-29-2006, 06:42 PM
I looked at BUZZ'z link. It reminded me of my cars in the 40's and 50's.

I had a problem with my '79 bolens with a kohler engine. Its sytem was quite different. It used magnets in the flywheel with coils around the flywheel. This generates AC which goes to the rectifier/regulator. As I remember, it used a 'silicon controlled rectifier' (SCR for short) which is turned on to charge the battery or not turned on if the battery gets up to max volteage (around 14.5 volts). This is all electronic.

I haven't had a regulator fail since I replaced that SCR on the bolens. But I did have the charge diode fail on an unregulated briggs engine used on my gilson.

It seem to me the age and type of engine may affect what your charge system is.

All the modern mowers that I have seen have only a low output alternator and a charge diode if they have a manual pto. If they have an electric pto, the engine gets a high output, regulated charge system.

To check the system, I just put a voltmeter on the battery. It should be around 12.5 (maybe 13) volts before starting the engine. After starting, the voltage should climb to 14.5 volts fairly quickly, if you started with a charged battery.

If the regulator doesn't charge, then the running voltage will be low. If it overcharges, the battery will run dry and fail. This is regardless of the design of the regulator and/or charge system.