cub cadet rzt50 pto switch problems

rdaystromApril 20, 2010

My nephew has a Cub Cadet RZT50. The deck would not turn on so I traced the problem to the pull out PTO switch. I replaced it and it lasted only 2 hours. We thought it was defective and replaced it again. The 2nd switch lasted 20 minutes and this time smoke came out of the switch. What could cause this?

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One would wonder how the clutch itself checks out IE resistance, gap etc. I don't know if Cub uses a diode in the pto harness like some or not. Worth at least a look.

    Bookmark   April 20, 2010 at 11:11PM
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I was wondering if there was a diode or something else that may have gone bad. The clutch engaged very good and instantly with no slip before the switch went out. I plan to measure the resistance across the clutch coil soon. Don't really know what the reading should be though.

    Bookmark   April 21, 2010 at 3:38AM
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Please keep us posted on your finding and results. Alot of us have elect. clutches and this will be valueable information for us.

    Bookmark   April 21, 2010 at 5:36AM
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This is my first experience with this weird electric clutch/pto-switch problem. I would think it would blow a fuse before burning out the switch contacts. When I get a resistance reading on the clutch coil I will go to the parts store and measure a new clutch if they have one and compare readings. I wonder if there is some kind of electrical component (diode or resistor) in the harness I am not aware of that affects the clutch?

    Bookmark   April 21, 2010 at 2:28PM
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You will probably need the ZTR's wiring diagram to know for sure. You could trace the wires from the elect. clutch to the switch and any where else they lead. Might have to take the side covers off. I sure there are a bunch of stuff it wired through.

I would also measure the output of the regulator/alt.. I can't remember what amps a elect. clutch model produces but it's more than a manual (15 amps vs. 10 ???). Something IMO is causing too much Amps to the button. I am guessing it got to be the elect clutch pulling too much or the regulator/alt producing too much? outside change something in the system is causing a dead short also increasing the amps?

    Bookmark   April 21, 2010 at 2:52PM
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For a wiring schematic,go to Cub Cadets web sight and with model and serial number,you can print one out. It took me a while to figure how to do it,but its worth the effort,as you can blow it up to really trace the wires. I think they also have tecks,that can help you also. Since this is my first electric pto,am paying attention to all postings.

    Bookmark   April 22, 2010 at 6:54PM
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There is a Warner clutch manual floating around here which may be helpful. I know they have a resistence spec, and other helpful troubleshooting steps in it. I don't have anything specific to MTD myself on these. I wonder also if it would be a good practice to trace and secure the ground wire for the clutch and body.

    Bookmark   April 23, 2010 at 9:53AM
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I would love to hear the feedback from what you found out.
I have the same mower (2004) and the PTO stopped working today. I cut for two hours yesterday and today nothing. I tried to test the wires, but I have no knowledge about stuff like this.
Other than the PTO not working, the mower runs great.
Thanks in advance.

    Bookmark   April 23, 2010 at 4:56PM
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Took a while but I finally figured it out. The resistance across the terminals on the clutch showed 1.5 ohms. The new clutch at the parts store measured 3.5 ohms. Even so I constructed a wiring harness separate from anything else and complete with a fuse holder. The clutch would blow 10 amp fuses but not 15 amp. Well that's what I thought anyway. After some use the bigger fuses started blowing right away. Time for a clutch.

    Bookmark   May 3, 2010 at 11:38AM
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I would love to have the know-how to do that rdaystrom, but I do not.....
I replaced my PTO switch with a new one. Got about 3 hours into mowing (over the course of two weeks) and it blades shut down on me again. I checked the plug that the switch plugs into with a staple. As I turned the key, you could hear the elec clutch click. I do not know what do to...
Thanks for any help or links..


    Bookmark   May 5, 2010 at 7:54PM
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The clutch coil is slowly shorting and even though you and I were able to get it going. The switch, fuses, and wiring will keep burning out as long as the coil is shorted. A new electric clutch ($250) is the answer. The clutch comes with a new coil that pulls less current (it's not shorted) and will not blow fuses. The odd part in this whole affair was that the PTO switch would blow or burn out before the fuse would blow. I think a PTO switch should be able to handle more current.

    Bookmark   May 6, 2010 at 7:10AM
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***"I think a PTO switch should be able to handle more current."***
Justifiable thinking (and wishing). I too believe that any switch in an electrical system, and the wiring, connector terminals, etcetera...........should have an ampacity at least 3 X greater than the fuse ampacity and be able to tolerate a continuous electrical load of 1.5 X the fuse rating without damage. But it seems that the design engineers are more about engineering for low cost assembly and build to get the product to market instead of other concerns about costs to the consumer later.
Using the PTO clutch as an example of my opinion, a typical PTO clutch in good working order will draw no more than about 4 Amp. Factor in a wider than perfect air gap and the current draw may edge up to near 5 Amp. While 5 Amp draw will not cause a 10 or 15 Amp fuse to fail, it seems that any current draw higher than 5 Amp WILL cause early failure to a lot of the PTO switches in today's lawn tractors (that too is just my opinion, based on threads to this forum).
The OEMs are not likely to provide a solution to the problem on units already in the field, nor to begin building with heavier duty PTO switches......ever.
For the consumer who is handy/savvy enough to do some custom wiring on their tractor, a 30 amp Bosch style, 5 pin, aftermarket relay could be added to the PTO wiring that would remove 100% of the clutch load from the PTO switch while leaving the OPERATION of the PTO controls exactly as OEM built it. And the total cost of parts to do so would be around $15 (or less). Addition of the relay would not interfere with the OEM fuse from blowing if a "genuine short" occurred.
Some of the posts regarding failed PTO switches imply that there might be a marketing strategy in place to bolster sales of replacement parts (again, my opinion). It has been posted in the past that a trip to the OEM parts center for a replacement PTO switch revealed the item stocked in large quantities. That is something that more or less declares the item to have a very high failure rate. You can usually infer that the "stockable quantity" of any item on the inventory ledger reflects the expected number of unit sales during a single ordering cycle (30 to 90 days avg.)

    Bookmark   May 6, 2010 at 9:43AM
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How could one go about checking the AMP on the clutch? Im not handy when it comes to these items. Trying to learn but do not want to mess anything up.
Also (on my mower) in addition to the three relays, a 20 amp fuse is wired off the Set relay (found here on figure 15.7 )

Going to try a 25 to see. But, I like the idea of aftermarket relay, but would have no idea how to wire it.
Just do not want to drop the money for the clutch if I can get around it. However, my grass keeps on a growing.

Great ideas folks..

    Bookmark   May 10, 2010 at 9:44AM
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I have a PDF manual for testing the PTO clutch. I am sending a copy to you.
Now, please explain what you mean by "Going to try a 25 to see.".
Do you mean you are going to try a 25 Amp fuse in place of the 20 Amp fuse? If that is true, DO NOT DO THAT! Replacing a fuse with a larger ampacity fuse is a good way to burn up the wiring harness and/or the entire machine.

    Bookmark   May 10, 2010 at 12:08PM
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yep. That is what I was going to do :)
I guess I should not.
Thanks for the pdf. I will work to check it out this evening.
That is what I was looking for.

    Bookmark   May 10, 2010 at 12:41PM
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I will study the wiring diagram in the Cub manual to try and outline a step X step test procedure to determine a probable cause.

    Bookmark   May 10, 2010 at 1:10PM
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I am too have intermittent PTO starting problems. I disconnected the PTO connector and the voltage was 14 volts. So I am assuming the PTO must be bad. I checked the PTO coil resistance and it was 4.2 ohms, which seams good to me. I don't know weather to get a new PTO or a new switch? I am definitely going to install a relay off the switch. Any suggestions on how to check the PTO? Then when I was taking it back to my shed it started working and I got my yard mowed. Do you have a pdf of a LT1042 wiring?

    Bookmark   May 25, 2010 at 9:45PM
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My PTO Clutch Manual says: "If the clutch reads below 2.4 Ohms or greater than 2.9 Ohms, the clutch has failed and needs to be replaced."

    Bookmark   May 26, 2010 at 1:40AM
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I have a similar problem with my pot on a RZT50, I have replaced the pto switch, the pto clutch, and the switches which interrupt the pto when mower is put in reverse. The pto still does not work, I know that there is power getting to the pto clutch via a continuity check of switch anyone have any ideas?

    Bookmark   June 3, 2010 at 7:52PM
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Sometimes things can be diagnosed backward. Try this. Get a couple wires and hook temporarily to the battery + and -. (Put a fuse inline if you want to be safe.) Run your temporary wire to the electric clutch connector and carefully touch the wires (+ and -) to the contacts momentarily. Your clutch should click on and off when the wires are touched to the contacts. If it doesn't your clutch doesn't work. Simple. My guess is that your temporary wires will show you have a good clutch. If so I would investigate other "safety" switches like the ones on the steering handles. I have seen those go bad.

    Bookmark   June 4, 2010 at 2:18AM
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