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I can unplug pto and it runs great. my question is,how is the best way to determine if the pto has shorted itself out and feeding back? I have replaced the battery and pto switch.

Just replaced a clutch on a scag last year for the same reason. Take on ohm meter and check the resistance across the two wires. Should read in the range of 2.4-3.4 ohms. Any higher or lower indicates a problem with the clutch. Also while testing go from one of the wires to the housing of the clutch and see if you have continuity. continuity indicates a short.

IlEngine seems to have a very good answer for you. You can test the clutch like he has explained.
One more thought for you...If you disconnect the wiring plug from the clutch and start your mower, then operate the PTO switch and the fuse doesn't blow...you pretty much isolated it down to the PTO clutch as being the problem. Wish you well on your experience. Enjoy your week!

jerry1249 said:

I can unplug pto and it runs great. my question is,how is the best way to determine if the pto has shorted itself out and feeding back? I have replaced the battery and pto switch.

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thanx guys. I've usually manage to solve these things but one really stumped me. will have mowing now in no time. thank you both. Jerry

ILENGINE said:

Just replaced a clutch on a scag last year for the same reason. Take on ohm meter and check the resistance across the two wires. Should read in the range of 2.4-3.4 ohms. Any higher or lower indicates a problem with the clutch. Also while testing go from one of the wires to the housing of the clutch and see if you have continuity. continuity indicates a short.

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I just replaced a Kholer 25 HP from OPE and was advised I should install a clamping diode in front of clutch itself to prevent back feeding spikes into electrical system when PTO is engaged.
$12.00
Kohler Part # 2575540S Clamping Diode Kit 25 755 40-S

Check the charging and the battery as well. There are different specs for the different clutches used so keep that in mind while doing your ohms test. You can also do the amp draw test as well so see how it is drawing and that also depends on which clutch you have as well.

We have had fuse issues more than one time also on our Scags. We solved a long going fuse blowing problem by changing the fuse holders out. The old ones did not really look that bad but apparently they had an issue because when we change the fuse holders we stopped blowing fuses on that machine.

ILENGINE said:

Just replaced a clutch on a scag last year for the same reason. Take on ohm meter and check the resistance across the two wires. Should read in the range of 2.4-3.4 ohms. Any higher or lower indicates a problem with the clutch. Also while testing go from one of the wires to the housing of the clutch and see if you have continuity. continuity indicates a short.

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So...since my PTO unit shows 2.2 ohms and I blow fuses when I engage the PTO, I guess my PTO is shorting out.

I already replaced the switch..fixed it for about an HOUR. Then it started blowing fuses when I engage the PTO.

I may be destined for an expensive PTO replacement it seems???? Give it to me straight fellas.

Yep it's replacement time below specs

Kev71h said:

So...since my PTO unit shows 2.2 ohms and I blow fuses when I engage the PTO, I guess my PTO is shorting out.

I already replaced the switch..fixed it for about an HOUR. Then it started blowing fuses when I engage the PTO.

I may be destined for an expensive PTO replacement it seems???? Give it to me straight fellas.

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5.5 amp draw calculated isn't that far out of spec. But that could go up when the clutch heats up. Did one on a DR field mower a couple weeks ago with an ohm reading of .5 ohms. which caused some serious wiring issues.

ILENGINE said:

5.5 amp draw calculated isn't that far out of spec. But that could go up when the clutch heats up. Did one on a DR field mower a couple weeks ago with an ohm reading of .5 ohms. which caused some serious wiring issues.

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Would it be interesting to note that my Tiger Cub is a 2004 (I think) with only 441 hours on it?

When it comes to electric clutches hours don't seem to matter. One will go over 1000 hours and the next less than 50. It seems the first symptom a lot of time when the clutch is going bad is it takes out the pto switch, but not bad enough to blow the fuse.

Had a grasshopper this year that killed the pto switch but never blew the 10 amp fuse. Clutch tested 1.6 ohms which is around 7.5 amp draw. DR with the shorted clutch had a 20 amp fuse connected between the 20 amp voltage regulator and the battery. The only way that fuse was going to blow was if the regulator shorted to ground. The constant 20 amp output of the regulator due to the shorted clutch actually melted the fuse holder.