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Heliarc 
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Joined: 23 Jun 2019
Location: Shickshinny PA
Points: 32
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 Topic: Onan twin CCK not charging
Posted: 06 May 2025 at 1:08pm |
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Working with an AC 720. It has an Onan CCK engine. It's only putting out about 5.5VDC. Is this the alternator/generator done for or should I be looking elsewhere?
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den/southern illinoi
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Joined: 11 Sep 2009
Location: Sparta, Illinoi
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Posted: 06 May 2025 at 2:51pm |
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I do not know the answer to your question but was told where you can get new stators for these engines if it comes to that. If so, message me and I will get you the info.
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Own 4 wheel 20, 2-5015, 5020 and associated equipment and 2 electric forklifts.
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Heliarc
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Joined: 23 Jun 2019
Location: Shickshinny PA
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Posted: Yesterday at 6:31am |
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Understood. Looks like if I want to do the stator, ring with coils?? I'd be pulling the engine. Trying to start cheap and easy before I do all that.
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 85797
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Posted: 22 hours 31 minutes ago at 7:29pm |
does yours have a 3 wire regulator on the stator output ?
---------------- GOOGLE-----
The first thing to do is to check the charging fuse and make sure it is not blown.
If the fuse is good, locate the voltage regulator on the engine, near the starter. It is a small aluminum box with 3 terminals on it.
The 2 outside terminals are the AC input.
The center terminal is the DC output.
Use your meter to test for battery voltage at the center terminal. It should read about 12V.
If it does not, either the fuse is blown, or the wire is broken.
If it reads battery voltage, set your meter to ACV, and connect one lead to each of the outer terminals.
Start the engine, and run it to full throttle. You should read between 40 and 60 VAC.
If it does not, the stator is bad.
If you have good AC voltage going in to the regulator, set your meter back to DCV. Retest the center terminal for DCV. With the engine running full throttle, it should read 13.6 - 14.7 VDC.
If you have good AC voltage going in to the regulator, but no DC voltage coming out, the regulator is bad.
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Like them all, but love the "B"s.
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Heliarc
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Joined: 23 Jun 2019
Location: Shickshinny PA
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Posted: 3 hours 38 minutes ago at 2:22pm |
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I'll try and locate the regulator and see how many wires are on it.
Thank you very much for this! I was looking in the manuals I have on the tractor but it only tells you "alternator is bad, have a dealer replace". This is what I needed otherwise I'd be wasting time and money.
Edited by Heliarc - 3 hours 25 minutes ago at 2:35pm
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
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Posted: 2 hours 51 minutes ago at 3:09pm |
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If you have an OLDER MODEL... I might have a couple resistors / diodes taped together on the wires and not an actual "voltage reguator"... ....both the "regulator" and the older "resistor / diodes" have been known to fail ........... stator is a possibility, but its just a coil winding..
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Like them all, but love the "B"s.
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Heliarc
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Posted: 2 hours 39 minutes ago at 3:21pm |
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I don't know the year of the engine or if it's even the original. It's painted black outside and some kind of odd lime green/yellow inside the cooling shrouds.
Model number CCK MS-2733J if that helps. Looks like the regulator is available for the three wire setup. Undoubtedly Chinese or India manufacture. Hopefully a blown fuse or broken wire. I'll run the 40 year old original stuff if I have a choice.
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injpumpEd
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Joined: 13 Sep 2009
Location: Walnut IL
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Posted: 2 hours 38 minutes ago at 3:22pm |
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Been following this also, So I replaced my reg and rect last year due to no charging, and it didn't help, but I see above you mentioned a fuse. I should look into that, it's a pain charging the battery all the time lol! Those plugs for the reg/rect aren't easy to get to either, under the tractor and inside the belly pan. Wouldn't all 720's be the newer setup Steve? These mowers are irreplaceable, I use mine on a hillside on my property that a zero turn is very sketchy on, even with a 95# AC weight bolted on the back lol! Thanks for the info!
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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Heliarc
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Posted: 2 hours 17 minutes ago at 3:43pm |
 injpumpEd wrote:
under the tractor and inside the belly pan. |
Man I was afraid of something like that... I was just out looking all over the thing and couldn't find the regulator. The belly pan on mine isn't all that easy with the loader and backhoe on it.
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