Weird meter reading

PTmowerMech

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Murray 46103X92A
Briggs 42A707-2653 E1 (Opposed twin)

I had to replace the coil on this one. Afterwards, I got spark and it started right up. I can't say if I checked the charging system or not. But finally got it ready to mow, and other than having to choke it off and on, it seem to run ok. I put the meter on the battery, while it was running, and the numbers were changing so fast, I couldn't get an accurate reading. None the less, I wanted to check out how the carb ran and the new spindles & blades performed, so like a dummy, I mowed with it for about 30 minutes.
After letting it sit for about 30 minutes, I tried to start it, and was getting no spark. So I parked it for the night.

This morning, I'm getting fire. But after mowing with it a little more, I put the meter on it, and once again, the numbers are moving so fast, I can't get an accurate reading.
One thing I did notice, that I'm also getting voltage on the negative side of the battery. It's jumping around like it is when I've just got the leads to the battery.

Oh, and yesterday I noticed some fresh oil on top of the starter and down the side of the engine.
 

PTmowerMech

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I found the oil leak. The plate the holds the back cover on, was missing the bolt closest to the starter. I found another bolt for it. I hope that stops the leak. I doubt it will. But maybe.

Still trying to figure out why the meter is jumping like it is. The alternator was tight.
 

EngineMan

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You should be checking the regulator.
 

PTmowerMech

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I don't think this has one. Where would it be?
 

EngineMan

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Then you have a dual circuit with a diode with you have lights on it.
 

PTmowerMech

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Yes it's just the two alr. wires with diode.

Did I mention I'm getting power to the ground side of battery?
 

bertsmobile1

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Alternators generate AC electricity, which is why they are called ALTER-nators and not generators.
A diode is a one way valve for electricity so only the + section of the alternation goes to the battery.
IF the diode goes bad the wire to the battery will go from +13V to - 13 Volts and thus give you strange readings.
Pumping AC into a battery will destroy it in no time flat and of course as you recharge it then discharge it the recharge it then discharge it, it will never end up with a net charge, just get hot.
You can confirm this by poking a pin through the red wire an inch or so away from the diode ( alternator side ) and probing the red wire from the mower side of the plug ( plug disconneected ).
If it is good you will get continuity with the meter one way and no continuity when you swap the meter leads.
Yours will most likely read continuity in both directions.
 

PTmowerMech

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Thanks Bert. I'll check that out.

Here's the meter reading I get from the battery posts and the wires from from the alternator.
https://www.youtube.com/watch?v=24HuUJiUbwE

Also, I put a test light on the two wires from from the Alt., and it lights up on both wires. One side lights up much brighter than the other.

UPDATE: Bert, I did the test like you said, and didn't get continuity from either way, when touching just the pin and the connection. But, with the pin through the red wire, about an inch back from the diode, I did get continuity when I touched the other lead. Even when I switched them.

BTW, I get juice to the negative side of the battery, ONLY when the engine is running.

With that said, it can only be the stater or diode, right?
 
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PTmowerMech

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Any help you guys could give me, would be great. Could this be a bad alternator? A hot wire grounding out?
 

EngineMan

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Take off one lead from the diode and check again for continuity one way only.
 
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