Gravely Rapid XZ Model 990101 PTO problems

[darrels]

Sorry if this gets technical...I have been having problems with the PTO (blades) not engaging when I pull out the PTO switch. Sometimes it works. Other times it doesn't. What I've done:

1) replaced the PTO switch as I didn't think it was working when I checked continuity. However, I may have wasted my money on that as the old one worked after I pulled it out.
2) bypassed the seat sensor, to no avail. Put back to normal operating configuration and ruled out that sensor.
3) bypassed the deck position sensor, to no avail. Put back to normal operating configuration and ruled out that sensor.
4) tested to ensure that the mower would not start if the PTO switch is pulled out (it would not), and that the mower will die if the PTO switch is pulled out and I lift my weight from the seat (it died).
5) checked resistance through the electromagnetic clutch. (2.0 Ohms)
6) powered the clutch via a 12v battery charger and the PTO engages every time starting the blades (so based on the resistance reading and this test, I ruled out the clutch)
7) checked voltage at the connector where the wiring harness plugs into the clutch. At times, it read 12v. Other times I get nothing, so no power there intermittently.
8) checked continuity through all 5 relays in the deenergized state, and all passed.
9) checked continuity for all 5 relays in the energized state. 4 of the 5 passed. The PTO relay did not (no continuity on the proper terminals when energized).
10) swapped another working relay onto the PTO relay harness. It failed continuity on the energized terminals. Since I know the relay was working properly on another part of the harness, I ruled out the relay.
11) Based on the wiring diagram, it looks like power should come into that relay on the purple wire (post 30) and exit out on the Purple/white wire (post 87) when in the energized state.
12) I did have a bad battery (factory original died from age and the cold temps over winter). I replaced it, hoping that maybe the old battery wasn't able to always provide 12v to activate the relay. No joy...

So where do I go now? Any advice would be appreciated! I did not try to see if there is power coming into the PTO relay on the purple wire. Does this problem sound like a short somewhere in the wiring harness? Possibly a bad ground somewhere? Everything else on the mower (every control, light, etc. works perfectly).

Thanks for ANY help you can provide. Short of some good suggestions here, I am about to either replace the entire wiring harness or take it to a local mower repair shop. They are not Gravely people, but an electrical problem like this shouldn't require a lot of brand specific knowledge. Thanks again.

By the way, the wiring diagram and continuity diagram are available on www.billspowercenter.com. That is a GREAT site. Many kudos to them!

 

[darrels]

After work tonight I went wire by wire checking for continuity. I found that the deck position sensor works some times but doesn't work at other times. I hate intermittent problems like that! So everything is good now! Thanks for reading this thread!

 

[clyttle]

try using the up side of the auto level switch (the switch to the right of the on/off switch on the control board) and lift the plate on the mower attachment and make sure the switch on the back right side is making contact, sometimes just pushing up and letting go several times of the button switch will work

 

[retired911guy]

I have a 4 year old Rapid XZ model 990100 w/ 27 Hp Kohler and 72 inch X-Factor deck and I have just experienced the same problem. I was mowing for first time this year and everything started out fine, no problems. After about 30 minutes of mowing, the deck just quit, instantaneously. No warning, it just quit. I downloaded the service manual and dived into diagnosing the problem. I did many of the same checks as you and came up with the same answer. Basically, no answer, no reason. I talked to 2 different dealers and got no definitive answer. I went to a dealer today and bought 2 relays, the diode located on the left rear frame rail with the wires going to the PTO clutch and the PTO switch to the tune of $67. My gut instinct is telling me I wasted my money but as soon as it quits raining, I guess I will find out. The dealer said the most common culprit is the PTO switch and is almost never the PTO clutch; they have a very low failure rate (hopefully, that is true in my case because they cost somewhere between $200 and $450). One thing worth noting: shortly after I bought the mower, the deck would not operate and it was the deck safety switch that was the problem and it was replaced. Maybe it's acting up again? Hmmmm. This time I bypassed it (I think) but did not test it for continuity by operating the switch manually. I will try that tomorrow. $13,000 mower that won't mow because of a (probably) mysterious $10 part!

 

[inthechateau]

I've never seen a $10 part on a gravely, most of them start at $69.95, lol, love to hear if you got it fixed or not and what you ended up finding.

 

[retired911guy]

Just think of the worst case scenario and Murphy's Law and anyone could figure it out. Of course it was the almost $500 clutch. I fixed it myself and believe it or not, it was surprisingly easy. Still a pain, but relatively easy. A 1/2" pull/breaker bar and a short piece of pipe as a handle extension to move the belt tensioner and it was a snap! I also just experience a problem with the hydrostatic drive oil. It disappeared! 390 hrs. on the machine and no problems. So I brought it up to full and parked it (too wet to mow right then). Imagine my confusion when the sucker wouldn't move an inch! The oil tank was empty and there was a big oily spot on the ground. So I got down on my titanium knees and looked with a flashlight. Oil dripping steadily from the right side hydraulic pump. Oh, CRAP! What to do? New pump is $900.00 I got a can of brake cleaner and sprayed it off. Hmmm. The oil seemed to be seeping from under some kind of a cast aluminum "cap" with a cast-in hex fitting on the front end of the pump. Tried to turn it with my fingers and it turned easily and oil seeped faster. Got out my trusty adjustable wrench and tightened that rascal up. Voila! No more leak! $900 saved! Now if I can figure out how water got in the hydraulic oil as the oil in the tank turns milky white when it's running...?