Zero turn runs until it is in full throttle and then blows 20 amp fuse

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Old 08-22-18, 04:29 PM
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Zero turn runs until it is in full throttle and then blows 20 amp fuse

I have a Husqvarna ZT5424 wiht a Kohler courage 24 hp motor. I t has been running great, not used for a few weeks due to drought here in the Midwest. when it was started it ran until full throttle was applied and the 20 amp fuse blows. All wires have been checked for ground when running and there are not rubbed through wires. It only happens when full throttle is engaged and the blade engagement works fine, and does not blow the fuse. I have worked on small and large engines through my entire life and never ran across this one. The engine runs a little rough but it is 6 seasons old and has some blow by that makes the engine shake but evenly, like the felling of a small cam. The mower belongs to my 90 year old Farther in law across the street. I ma stumped. I have all diagnostic tools.
 
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Old 08-22-18, 06:08 PM
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The stator output voltage increases with increased engine RPM. The stator output goes to a regulator. The regulator or the stator may be bad. I don't have a schematic but there must be a way to electrically disconnect the stator from the regulator. Run the engine at RPM that blows the fuse. If fuse blows, stator is good. Reconnect stator to regulator and electrically disconnect regulator from battery. Run the engine at RPM that blows the fuse. If fuse blows, regulator is good. If this doesn't find the problem, I am lost also. I am assuming the 40A fuse does not power the starter.
 
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Old 08-27-18, 08:36 AM
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Found a lot of debris in the alternator. Cleaned it. It finally stopped running all together and fuse did not blow. Chased it back to the ignition switch. The was a lot of debris in it. I get 12 volts to the ignition but when the key is turned all power is lost. Have a new one on the way.
 
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Old 08-27-18, 01:58 PM
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After cleaning debris from alternator did you duplicate RPMs that blew the 20A fuse earlier or did the engine stop running before that RPM was reached? It is possible a piece of wire (metal) could have been in the debris removed, but only causing a short at high RPM is still a mystery.
 
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Old 09-04-18, 08:31 AM
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I ran the RPMs up to full again and for 30-60 seconds it ran and then did the same thing. I replaced the ignition switch and it we can get it to run at 3/4 throttle. I spoke with a mechanic buddy yesterday and he gave me a sealed beam light from an automobile, round old school one. He informed me that the light will take the load and will be super bright and that the fuse should not blow because the light is the load, and it will not burn the wire, or shouldn't. I plan on working on it today.
 
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Old 09-04-18, 12:26 PM
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Did you ever perform the advice given in post #2 about unplugging the regulator? The light trick won't really tell you what the problem is, not sure what the purpose is.
 
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Old 09-10-18, 07:42 AM
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No, for some reason I did not see that. But, I did find that the light worked long enough to see at full throttle the DC volts went from 12.7 to 24.3. I then pulled the regulator and the left A/C post was shorted to the DC post.
Beelezbob, sorry I missed your help in number 2, I could have saved some time for sure. Yes there is a way to isolate regulator and stater via a plug between them on the motor. I will not forget this anytime soon. Thanks.
 
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