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Discussion Starter #1
I thought I had a manual, but can't find it.

First attempt to mow the lawn yesterday revealed a front PTO that didn't actuate. Worked fine last season. Checked power to it, and there's power when the switch is activated right at the wire plug going to the PTO. Tried running a hot wire to it, and that didn't activate it, either.

It looks like it's obvious I'll have to pull it, so what is the procedure on a Sunstar? Looks like a single bolt holding on the 2 pulleys on the PTO output shaft, do I just remove the bolt, slide/pull the pulleys off, then just un-bolt the PTO?

What is the resistance check for this type of PTO?

Kind of surprised it might be bad, how often do these things go, and are they rebuildable?
 

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Those PTO clutches are pretty reliable, in my experience. Mowman1 is right that the air gap needs to be adjusted correctly. Warner says to adjust to .012" and that the resistance across the coil should be between 2.40 ohms and 2.90 ohms.

Yes, you remove the center bolt and slide the pulley off. Use an impact wrench or you can simply use a hammer and tap on a 5/8" box end wrench or a ratchet wrench.

I'll attach a copy of the Warner Troubleshooting Guide.

Gerald
 

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Discussion Starter #6
You are welcome. Mine have Warners, I don't know about others. Does yours look like the one in the document?

Gerald
Mine DOES look like the pics, except it has a 2-row pulley.

However, in Figure 1 that describes the resistance check, my wire going to the PTO is a SINGLE wire, unless there's another wire on the other side I didn't see. I assumed it got power thru this single wire and grounded thru the mounting.

If mine is correct and only a single wire is used, can I assume the resistance check is still valid, and I would just check across this wire and the mounting surface?
 

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Mine DOES look like the pics, except it has a 2-row pulley.

However, in Figure 1 that describes the resistance check, my wire going to the PTO is a SINGLE wire, unless there's another wire on the other side I didn't see. I assumed it got power thru this single wire and grounded thru the mounting.

If mine is correct and only a single wire is used, can I assume the resistance check is still valid, and I would just check across this wire and the mounting surface?
What is the model number of your tractor? The early Sunstars used a PTO clutch that had one wire coming out of each side. Later, they had two wires coming out of one side. I never saw one that had only one wire and used the frame as ground. Sometimes the wires will break at the point where they exit the clutch. I usually reinforce the wires at those exit points (with shrink tubing or elec. tape).

Gerald
 

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Discussion Starter #8
Hmmmm, rainy and cold, I haven't looked to see the model #, but I'll assume it's the model with a wire on each side, I just need to look on the other side for the wire.

So the wire I DO see on the right has power to it when I hit the PTO switch. Does the other wire run to ground? Maybe that's the problem.....

I noticed when I first discovered the problem that the REAR PTO doesn't activate, either. Used to work fine. I haven't checked power to it like I did the front, but it now seems weird that BOTH PTOs would stop operating, unless it's a common problem.
 

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Hmmmm, rainy and cold, I haven't looked to see the model #, but I'll assume it's the model with a wire on each side, I just need to look on the other side for the wire.

So the wire I DO see on the right has power to it when I hit the PTO switch. Does the other wire run to ground? Maybe that's the problem.....

I noticed when I first discovered the problem that the REAR PTO doesn't activate, either. Used to work fine. I haven't checked power to it like I did the front, but it now seems weird that BOTH PTOs would stop operating, unless it's a common problem.
Sounds like you have safety interlock problem of some sort which is preventing the left side from getting the ground it needs to activate the coil (assuming you do have the model which has a separate left/right wire on your clutch). So, if you apply ground to that left side wire, and have +12V on the right side wire, the PTO should activate. You can do this with the engine off; just ground the left side wire, turn the key on and the PTO sw. on to get +12V to the right side wire. You should hear the PTO activate (click).

I'll attach a copy of the wiring diagram for early Sunstars (like one of mine, a 1691018).

Gerald
 

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Discussion Starter #10
So, if you apply ground to that left side wire, and have +12V on the right side wire, the PTO should activate. You can do this with the engine off; just ground the left side wire, turn the key on and the PTO sw. on to get +12V to the right side wire. You should hear the PTO activate (click).
Gerald
Thanks for the diagram and sanity-check for the ground. I'll check continuity from the ground wire to the chassis, but do the jumper-check anyway straight from the +/- of the battery to the PTO. If it doesn't work then I'll go back to suspecting the PTO itself.

Thanks a million for engaging in this discussion. My frustration level on the day I discovered the PTO wouldn't activate was off the charts, as it was the ONLY day in a 2-week span that it wasn't raining and I had the time to mow. What also contributed to a bad day overall was that my OTHER, back-up tractor (Ariens S-16H) that had been purring like a kitten all year but was currently without it's deck installed, DECIDED TO NOT START THAT VERY DAY. Traced it to a suddenly non-functioning fuel pump (Kohler K341 engine), but that was my last shot, and now the grass is 10" tall and no dry weather in sight.
 

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Discussion Starter #11
OK then! So I checked ground on the PTO ground wire with the key on and the PTO switch engaged....no ground.

Then I pulled the sidecover off, cleaned the VERY nasty and corroded Insterlock plug connection, cleaned the PTO switch plug, then re-plugged everything and check resistance of the PTO itself per the manual G-1 provided. Good range was 2.4 - 2.9 ohms, mine checked 3.0 ohms. :fing20:

But I started it anyway and hit the PTO.....wait for it......and it worked! The rear one works now, too!

So it came down to basic maintenance and the interlock plug connection, which G-1 suspected. I'm happy now!

I'm still mildly concerned that the coil tested out @ 3.0 ohms, but as long as it actuates I won't investigate further.

And, now I'm familiar with my PTO wiring!
 

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Possibly the additional resistance could be due to remaining corrosion in the plug. You'll get a small amount of voltage drop in the connector but doubt its a problem.

If I were you, I would consider using a silicone dielectric grease*in the future to help kerp out moisture and prevent corrosion.
 

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Thanks for the information here. I"m fixing up my dads old Sunstar. I got it running this weekend but the front PTO is not working. I'll be following all the steps here and see what the problem is. I was looking for the wiring diagrams as well. I'll let you know how it goes. Thanks!!!!
 

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So I checked my PTO last night. The resistance checked out at 2.5 ohm. Then I put 12V directly to the PTO with the engine off and heard a loud thunk. So it will engage if it gets 12V. So I'm thinking its an interlock thing as you mentioned above. Do you have any advice for trouble shooting the interlock?
 

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You said you applied 12V to the PTO; did you ground the other PTO wire? If not, and it worked then you would need to trace the 12V wires back to the PTO sw. If you did ground the other wire, then you need to trace back to the interlock mod and also verify that the mod is providing ground on the PTO ground pin. (2nd from right, upper row.) If no ground coming from mod, then check the mod's inputs. I'll attach a wiring diagram.
Gerald
 

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Thanks G-1. I looked at it last night and the ground for the PTO is bolted to the frame and then back to the control module PTO GND. I could un- bolt that wire to the frame if you think that could be part of the problem. But I'm thinking that the 12V power is not getting to the PTO. The neutral light comes on, the seat switches are permanently bypassed - Dad took those out years ago and wire nutted the wires together. Also the fuel gauge and voltage meter don't read anything. It does run ok. Any ideas of what the problem could be?
 

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Actually after studying the diagram a little further, all those things are connected to the rectifier. Is it possible that I have a bad rectifier? I have a DC clamp on Amp meter and there was not much battery charging going on either. Only about .2 amps.
 

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So, if you jumper 12V to the positive side of the PTO clutch (I assume right at the clutch itself), then the clutch engages? That means somewhere between the PTO switch and the clutch you are losing 12V. Looking at the schematic, the flow is from the ignition sw. rectifier pin to the middle pin B on the PTO sw, then thru the PTO sw. (pin B to pin A) and then directly to the PTO clutch.

The rectifier is not likely to be a factor in your problem. Since your clutch will engage, I would worry about the charging rate as a separate matter. Keep in mind that if the clutch air gap is too wide, you could expect to see erratic operation of the clutch. Might be a good idea to check its adjustment at some point in your getting your machine back to work.
Gerald
 

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Thanks G-1. I went out this weekend to trace down the wires and guess what I found. I had switched two wires on the solenoid and the circuit breaker when I was cleaning the contacts. I swapped them back and all the gauges came back. I thought I had it all set, went to start it and the starter motor wouldn't engage. Crap. It just was spinning without engaging the flywheel Went to the parts store and got a battery charger thinking there wasn't enough juice but after 5 hours of charging it was the same old thing.

So I went to see my parents for Mothers' Day today and told dad what had been going on. He said that I should spray some oil into the pinion gear and see if that does any good. Wouldn't you know it, I got home and one little squirt in there, turned it over and it started right up. I'm using bicycle chain lube on all the linkages and it seems to be working very well. I also adjusted the clearance on the clutch to .015 as you suggested. And the PTO worked as well! Back to 100% operation. Now I can start putting it all back together and just in time because the grass is getting long.

Thanks again for your help and the wiring diagram. Could not have done it without that. _ Rob
 
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