PTO switching problem?

Tue Sep 17, 2013 10:15 pm

On one of my 184's, I run a full time IH 3160 mower. My problem is that after mowing for a while, if the pto is either switched off, or the tractor is stalled, the pto clutch will not come on and engage. If everything is allowed to cool off, it will properly switch on.

Is this a switch issue, or worse, a pto electrical problem?

Any trouble shooting tips or diagnosis?


Re: PTO switching problem?

Wed Sep 18, 2013 8:14 am

If I had to guess, and that's all I'm doing, I'd say the clutch coil is going/gone bad. When it's warm enough and won't engage, test the coil with an ohm meter and test the switch for voltage, it could be a bad relay.

Re: PTO switching problem?

Wed Sep 18, 2013 8:20 am

Can't seem to fix it with a hammer, so it must be an electrical problem.

Some diagnostics will be required. Let's start with the easy stuff. We know that the PTO engages, so the electromagnet works when power is applied. When the issue is happening, make sure that 12V is being supplied to the electromagnet. There is a 6" pigtale with a connector coming out of the electromagnet. With the key on & engine off, verify that 12V is present at the connector when you flip the PTO Engagement switch. Note: Do not leave your key on for more than a minute or two.

If 12V is not present, then clean the terminals of the PTO Engagement switch and the terminals of the PTO Fuse. (must pull dash to get to these)
These PTO Engagement Switches do go bad so I wouldn't rule that out.
Clean the contacts of the fuse and fuse holder (inside) as well.
Clean the contacts of the pigtale connector and its mate.

Manually apply 12V to the electromagnet through the pigtale. You should hear the PTO engage. If it does not engage, then your issue is within the PTO Magnet itself. Replacing this assembly is quite pricey so I would look very carefully at the pigtale wires and the connector first. Again, it is unlikely that the assembly is bad because it works when cold.

One unlikely suspect may be the PTO Brake (built into the electromagnet assembly). This is adjusted with the three bolts (with springs on them). The tighter the bolts, the quicker the brake engages. Perhaps the PTO brake is becoming engaged and won't disengage. You can see the brake portion on the front side (engine side) of the PTO Assembly. You would have to examine how this works prior to warming up the tractor. Again - be careful not to leave the key on very long as you may damage the points.

Re: PTO switching problem?

Wed Sep 18, 2013 8:50 am

Thanks for the tips!
Very aggravating problem, especially when you need to finish up a section.

Re: PTO switching problem?

Wed Sep 18, 2013 9:17 am

I agree anything to do with these electric clutches can be expensive.
outdoors4evr wrote: it is unlikely that the assembly is bad because it works when cold.
These magnets are not that different from an ignition coil in that they both use coil windings of scantly insulated wire and after years of use will become weak and even develop a dead short rendering the appliance totally inoperative, and sometimes will cut out when warm/hot, and may work well when cold.

Re: PTO switching problem?

Mon Sep 30, 2013 8:43 am

I'd clean all the connections first. And make sure all the grounds are clean to the tractor frame to the battery from the PTO. If that doesn't work I'd run a jumper wire so your positive it's grounded. I'd really rule out a connection before going after the coil.