Snowmobile voltage output

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Decided to just start a new thread on the slow progress of my vintage 1974 OMC sleds. I recently switched in some insulated/resisted plugs, which allowed me to test the voltage output at the battery while running. Previously the interference was shutting down my multimeter. Anyway, while idling, 17 to 18 volts DC going to the battery. At around 4000rpm, 30+ volts. So my sled has a working rectifier, which is great but I cannot find a voltage regulator and it appears these sleds never had them. Is this kind of voltage hard on the battery? I am going to buy a new battery for the thing prior to snowfall but do not want to smoke one if I can help it.

Info: 437 cc twin, electric start, CDI ignition and 12 volt system.

Thanks!
 
I know nothing about snowmobiles , but I know a little about electricity in the automotive world .

I am wondering if the alternator / generator has an internal voltage regulator and it is defective ?

Also , if you have a friend with an analog ( swing needle ) meter , test the voltage again .
 
There should be a regulator in the electrical circuitry if there is a battery. Follow the stator harness and trace it back to the battery.
 
I would think a standard "shunt style" voltage regulator found on millions of riding lawnmowers, motorcycles, etc, etc could be wired in just fine
 
If you're running it without a battery, that may be causing the high voltage.

Motorcycles usually have a permanent magnet alternator with the stator wired to an external rectifier/regulator unit. You won't find anything inside the housing but the stator. The regulators usually have 3 wires input from the stator, and 1 wire + case ground output.
Originally Posted by Linctex
I would think a standard "shunt style" voltage regulator found on millions of riding lawnmowers, motorcycles, etc, etc could be wired in just fine

Absolutely.
 
Those readings are still wrong. With a bad regulator, the battery will clamp the voltage at around 16 volts. After a time of that, the battery will be damaged.
 
Well the battery in place currently is in poor shape, like probably toast. I will put in a better battery and retest. Linctex, thanks for the idea, I started looking at those simple regulators. Looks like a ground wire, input and an output wire. Possibly an easy add on.
 
Just an update, not sure it I had added it to my original thread. No voltage regulator on these sleds. What they used was higher wattage head/taillight bulbs to soak up excess current.

What I found was that the ignition switch had a couple positions, run/lights, run and start. On run/start, there is no power going to the lights. This is where I was testing and found the high voltage. When the switch is on the run/lights setting, the voltage is drastically different. Approx. 6 volts at idle and 15 when p1ss revved.
 
Most of the old sleds I've had over the years the lights were powered by ac voltage not DC. With the electric start models I think some of the rectifiers also had Regulators built into them. I never had a vintage electric start machine so I don't know that for sure but there has to be a way to regulate the DC going into charging the battery. There may only be a resistance wire powering the rectifier for charging the battery like the hot wire going to old GM ignition coils that did not use a ballast resistor like other brands
 
I am not sure what the AC voltage powers but the rectifier does work. I could not find a regulator but did verify a stark difference in DC voltage at the battery with the lights on and off. I guess I will run it with the lights on all times.
 
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