SCAG blade won't engage

[MrTee]

The belts are in tact and tight. I installed a new engage/disengage switch and that did nothing.

Sometimes my mower will cooperate but other times I can try 20 times to turn on the blades and nothing happens. Before, when it started doing this I found that if I left the blade button pulled up, let go of the handles just long enough for the engine to almost die, and then regrab the handles, the blades would engage. This trick doesn't always work. The other day I had completed one yard just fine and went over to cut beside the neighborhood pool when it started acting up. So I was cruising up and down the sidewalk with my engine dying and restarting constantly. It was so embarrassing. I ended up having to push mow my last 3 yards in the neighborhood. My local SCAG dealer is closed on the weekends and they charge a lot for repairs.

 

[BlazNT]

I would look at the wires going to the PTO. Unplug and clean all connections and see if that helps. I use an electric connector cleaner. At the auto parts store for cleaning the plugs. It will not arc the connections. Still let them dry before reassembly.

 

[ILENGINE]

Dying or trying to die with the blades engaged sounds like it could be seat switch related also. On scag's the seat switch is the brains of the operation.

 

[dnewton3]

No, the seat switch is not the "brains" of the unit. It's just a switch. I'd agree that it is trouble prone and often could benefit from a good cleaning or replacement.

The "brains" is actually a small electronic module that uses the various inputs (seat switch, neutrual switches, parking brake switch, clutch circuit sensor, low oil, etc) to know the current condition, and either allow or not allow other conditions to happen. In a very simplistic term, using automotive verbiage, it's the PCM (powertrain control module), of sorts. It's what the whole main wire harness plugs into.


If the clutch will not engage, but the engine will run and mower will move about without the engine dying, then it's probably not the seat switch. I do not recall directly (I don't have a manaul in front of me), but I don't think the seat switch actually has anything to do with the clutch circuit. The seat switch, when opened, kills the ignition. By default, the loss of engine power would stop the blades. And to restart the engine, the PCM looks for the PTO to be disengaged. But the seat switch does not directly affect the PTO circuit.

Check the contacts and harness for the PTO switch itself, from one end to the other. That's the easy (easy???) stuff to check first. From there, then you're into diagnosing the PCM. Get a manual and follow the wiring circuit diagram.

Essentially, for the PTO to successfully engage, the following must be satisfied:
1) engine running
2) brake off (circuit open)
3) ?? I don't recall if the neutral circuit needs to be closed or not; I'd have to see the manual. It seems to me that it does, but I'd not assure you of that until I reviewed it.

Mackie - do I have that right????


I have about 350 hours on my unit, and it's probably 12 years old. This summer I've had to take every single switch out and clean really well with contact cleaner, and then lube with dielectric grease before reassembly. I also replaced the starter relay last fall. So far, those things have fixed all the ills of intermittent activity I was experiencing.

I appreciate why there are so many safety circuits, but they do make for very intermittent use eventually. Someday, when my PCM finally dies, I'm ripping the entire wire package out, and going "ol skool" by only having a simple starter relay, a charge line, and a direct PTO link.

 

[Mad Mackie]

The belts are in tact and tight. I installed a new engage/disengage switch and that did nothing.

Sometimes my mower will cooperate but other times I can try 20 times to turn on the blades and nothing happens. Before, when it started doing this I found that if I left the blade button pulled up, let go of the handles just long enough for the engine to almost die, and then regrab the handles, the blades would engage. This trick doesn't always work. The other day I had completed one yard just fine and went over to cut beside the neighborhood pool when it started acting up. So I was cruising up and down the sidewalk with my engine dying and restarting constantly. It was so embarrassing. I ended up having to push mow my last 3 yards in the neighborhood. My local SCAG dealer is closed on the weekends and they charge a lot for repairs.

What is the model and serial number series of your Scag and the engine numbers and make?

 

[emo]

The belts are in tact and tight. I installed a new engage/disengage switch and that did nothing.

Sometimes my mower will cooperate but other times I can try 20 times to turn on the blades and nothing happens. Before, when it started doing this I found that if I left the blade button pulled up, let go of the handles just long enough for the engine to almost die, and then regrab the handles, the blades would engage. This trick doesn't always work. The other day I had completed one yard just fine and went over to cut beside the neighborhood pool when it started acting up. So I was cruising up and down the sidewalk with my engine dying and restarting constantly. It was so embarrassing. I ended up having to push mow my last 3 yards in the neighborhood. My local SCAG dealer is closed on the weekends and they charge a lot for repairs.

I would try checking the volts at the pto harness it could be an electrical problem ( emo ).

 

[Tried_it]

The belts are in tact and tight. I installed a new engage/disengage switch and that did nothing.

Sometimes my mower will cooperate but other times I can try 20 times to turn on the blades and nothing happens. Before, when it started doing this I found that if I left the blade button pulled up, let go of the handles just long enough for the engine to almost die, and then regrab the handles, the blades would engage. This trick doesn't always work. The other day I had completed one yard just fine and went over to cut beside the neighborhood pool when it started acting up. So I was cruising up and down the sidewalk with my engine dying and restarting constantly. It was so embarrassing. I ended up having to push mow my last 3 yards in the neighborhood. My local SCAG dealer is closed on the weekends and they charge a lot for repairs.

I had re-powered my 61" Turf Tiger and always had this problem prior to this project, and after. So I knew all connector harness were fine as well as other suggestions here.
I found on one of these forums someone posted to check the PTO clutch gap with feeler gauge, which should be between 012" and 014", mine was .025". Adjusted (tightened) the 3 PTO clutch nuts on springs evenly for .013" in sight hole and wala, after 5 years of no blades when hot now engage just fine, smoothly and silently.

I thank whoever posted this free fix.

 

[John R]

Anyone know how many hours on a clutch before it needs adjusting?

 

[BlazNT]

I check all of mine once a year. Anyone of the mowers I work on I adjust whenever I work on them. It has way more to do with starting it than running it.

 

[Southeastern Lawns]

I had re-powered my 61" Turf Tiger and always had this problem prior to this project, and after. So I knew all connector harness were fine as well as other suggestions here.
I found on one of these forums someone posted to check the PTO clutch gap with feeler gauge, which should be between 012" and 014", mine was .025". Adjusted (tightened) the 3 PTO clutch nuts on springs evenly for .013" in sight hole and wala, after 5 years of no blades when hot now engage just fine, smoothly and silently.

I thank whoever posted this free fix.

Thank you so much for this. I have been going crazy trying to figure out what what wrong with the blades on my Tiger Cub. The wires going to the clutch were severed a while back so I assumed it was an issue with my fixing the wires. Blades would work fine on the first lawn but stop working once warm. I read this, tightened the clutch bolts and bam. Problem solved!