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AC_B-1Novice

Al Eden or others question on these pics

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AC_B-1Novice
Here is a better shot of the wiring on that alternator. It looks like there is a diode on the wire but it looks like it goes into a fuse holder. Does this make sense or should I be wary of it? Also I have the repair manual but it doesn't show anything about this part. Is there somewhere I could get a picture and description of what this should be like? Thanks larry




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Al
Hi, You are correct. The diode has a little round disk on the cathode end. (the end with the cross bar) The anode (end with the arrow) is connected through the spring to the wire. The wire in the cap contacts the cathode end like it would contact the end of a fuse. It appears the the diode is correctly connected. If you straightened the leads out and put it back in the holder the spring would push the diode body and the little end cap out of the holder and the inside of th e cap would contact it and push it in a little ways. You would want to check the diode first. Do this by disconnecting the battery lead and take an ohmmeter and measure the resistance one way across the diode, then reverse the leads and you should have a very low resistance one way and a very high resistance when connected the other way. If the diode is shorted you will have very low resistance both ways. It the diode is open, you will have very high resistance both ways. Since the alternator puts out AC (alternating current) when the positive going peak exceeds the battery voltage (approx 12 volts, current will flow into the battery. As the voltage of the stator drops below battery voltage, the diode prevents current from flowing to the stator, discharging the battery. This happens until the stator voltage goes to 0 and then minus to 18 or 20 volts, then goes back to 0 and starts back up positive until the output reaches the battery level and goes above it to repeat the cycle. At 3600 rpm the engine is turning 60 turns a second. This would make this cycle repeat 60 times a second minimum, depending on the number of magnets in the flywheel and number of legs on the stator and how it is wound. In most cases, the 60 number would be correct. This is the most inefficient charging system and is called half wave rectification. If you go to my website edensltd.com and go to tech articles I have written several chapters on basic electric theory. I was just getting ready to do some sections on how to apply this information in practical trouble shooting situations. Then I got flooded out of my house June 2008 and am just getting it pretty well back together. Hopefully this winter I can add to it. Al Eden

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rsnik
Al, I just viewed your site. Your tech articles are great. Knowing how things work is the fastest way to increase your success at trouble shooting. Also, I did not realize your business is heavy on parts and parts expertise. That is great news.

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dentwizz
A bridge rectifier system would be a solution to that but it would take a little engineering. The bridge system would make the half that the single diode half-wave system blanks out correct and make it a full wave system. (correct me if I'm wrong but I think that's how it goes)8)

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Al
Hi, These engines have several charging systems. This is the lowest and I believe 3 apm max if I remember right. It has only about 1/2 a stator. You could update the engine with a different stator and a different regulator rectifier (which is full wave by the way)(and Josh you are correct). When you get in the newer units, the output current rating is determined by the size of the magnets. Also note that in the K series Kohler engines the 10 amp systems had 1 magnet missing and the 15 amp systems had all of them. In the Briggs, there are several different stator and regulator systems. Briggs has a real nice wall chart on charging systems. It lets you identify the stator by the color of the wires and type and color of plug on the end along with a picture of the stator.. I wish I could post it, but it is too big. Maybe this info may be available on the Briggs web site. Al Eden

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