# Trouble shooting Saftey system



## Toro-8-2-4 (Dec 28, 2013)

Does anyone know of a resource on the net that provide instruction on troubleshooting the electrical safety switch system on a Toro snow blower. Neural switch, auger switch, dead man switch etc.

I assume this is pretty generic from machine to machine and uses the same concepts on other equipment like riding mowers.

I acquired a Toro project snow blower and the previous owner said there were issues with the safety switches but he did not know specifics. 

I have not seen any for the short time I ran it, but I realize it could be intermittent. 

I am trying to get an idea of how the circuit works.

If I unplug the main connector coming off of the engine, will it start?


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## CarlB (Jan 2, 2011)

pretty simple as far as the electrical. When a switch is tripped it will ground the ignition coil and the engine will shut off. I haven't seen much in the way of electrical safety switches on snow blowers. They do normally have a kill switch that goes to ground when you push the throttle all the way down or if you pull the key out. Easiest way to find the kill switches is to follow the wire coming from the coil under the pull start cover on the left side of the engine when looking at it from the back. take the carb cover off and look in that area. If that wire shorts to ground the engine will stop. If you take the recoil starter cover off you will see the ignition coil and the wire. Some engines have a charging circuit but that wire normally exits behind the right side of the recoil cover when viewed from the back.


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## dbert (Aug 25, 2013)

My old craftsman driftbuster had two circuits from the coil to ground. One was via the key switch. Turn the key off and the coil was grounded and spark killed. 

The other circuit was more complicated. There were three switches in series. A left handle switch, right handle switch and auger engage lever switch all daisy chained together. If the left handle and the right handle were relaxed (not squeezed) the switches would close. If the auger lever was engaged it’s switch was closed. Meaning if you let go of both the left and the right handle levers (that have no other function on this machine) while the auger was engaged, the coil was grounded and engine would be shut down.


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## Grunt (Nov 11, 2013)

Here is a pic of the safety circuit used on the older Toro's. Disconnecting the single wire plug on the right side will disable the safety system.(Not a good idea). Hope this helps.


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## Toro-8-2-4 (Dec 28, 2013)

I believe the schematic that Grunt posted describes my machine. It is a bit complicated that it will not start if not in neutral or the auger is engaged. But when running the handle switch by passes the neutral switch and auger switch.

What does the Interlock module do? I assume it is the round device located on the engine block. Any way I can bench test it?


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## Shryp (Jan 1, 2011)

I don't know about Toro, but I know Ariens had an electrical interlock on their 70s blowers.

Before the switch over to the second auger lever and all the safety gizmos most snowblowers just had a "on/off" lever for the auger. The electrical interlock on Ariens was the first attempt at a safety device. There was a secondary lever on the handlebars that just contacted an electrical switch. If you had the auger lever locked down in the on position you had to either have the wheel drive lever down or the little interlock switch down. If both were released while the auger was engaged it would kill the engine.


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## UNDERTAKER (Dec 30, 2013)

The contact under the handle gets all mucked up or cracked. that is the main problem


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## Toro-8-2-4 (Dec 28, 2013)

I spent some time looking at it closer and it appears the interlock is some sort of solid state switch. If current is not passing through the safety switches on the handlebars is sends the signal from the magneto to ground. If the switches are made then current will make it's way back to the interlock and it does not ground the spark. I am not sure exactly how this works but I think I have a good enough understanding. 

As best as I can tell, the switches all look ok and make continuity for the few times I cycled them. If it is a true intermittent problem, I guess I will have to run it under load and see if it cuts out. 

I could make a jumper wire and put it across the interlock device, but I don't like doing that. Although, It is a strategy to help trouble shoot and isolate circuits should problems arise.

Thanks to all who replied.


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## Grunt (Nov 11, 2013)

If the auger is engaged, or the trans is in gear, the machine will not start, even if the handle lever is squeezed. Once the machine starts and the handle lever is squeezed, engaging the auger and\or trans is permitted. The handle lever when squeezed "opens" the kill circuit to the ignition coil while the trans "OR" auger are engaged. Releasing the handle when the auger "OR" trans are engaged, will kill the engine.


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## Toro-8-2-4 (Dec 28, 2013)

Grunt, from what I can tell through continuity testing, squeezing the handle lever closes the circuit going to the interlock switch. Having the transmission in neutral and the auger off at the same time does the same. Either condition will prevent the spark from going to ground and allow the engine to run. The auger and neutral switch which are in series with each other and the Handel lever is in parallel with them. The Key switch is wired in series with both and will override all.

I did not try it, but it appears the engine should start if the lever is squeezed and the key is on. (regardless of the state of the other switches) This would be awkward to do but I guess possible.

Again, I don't fully understand the details of how the round device called the "interlock switch" works but it appears if it sees a closed circuit coming from the handle bar controls it does NOT ground the spark. Otherwise it grounds the spark and kills the engine.

If I am missing something I am happy to be set straight and learn something new. Thanks.


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