How's An Ignition Switch Work?

[MikePA]

How\'s An Ignition Switch Work?

Specifically, in the Off position, no really. /forums/images/graemlins/smile.gif My Wheel Horse garden tractor wont shut off when the ignition switch is turned to the Off position. I have to pull the choke out to kill the engine. I've replaced the original ignition switch (20 years old!) and it still won't shut off. I have the wiring diagran and I am 'electrically challenged' and can't figure out how it's supposed to work, so I can't troubleshoot it.

 

[RobS]

Re: How\'s An Ignition Switch Work?

I'm kind of guessing here Mike, and I didn't even sleep in a Holiday Inn Express last night /forums/images/graemlins/confused.gif

Somehow the off position on such a simple system should ground the juice to the coil or eliminate the voltage to the coil. This will eliminate the spark which will obviously kill the engine. Without the grounded coil feed the engine continues to run. I'd say you've got some corroded/worn contacts in the switch itself.

Again, I'm hardly speaking from authority here /forums/images/graemlins/smile.gif

 

[Junkman]

Re: How\'s An Ignition Switch Work?

Without the wiring schematic, I can't say for certain. Most small engine ignition switches have a terminal that grounds out the magneto when you switch them off. If it has an electrical starter that is battery operated, the ignition switch make a connection through the starter solenoid to the batter to provide power to the starter to start the cranking. Once the engine starts, the spinning flywheel throws the Bendix drive (the gear that engages the flywheel that is mounted on the starter armature shaft) and then you let go of the key and it springs back to the "run" position. If there are points on the engine, then the starter switch breaks the connection to the positive side of the ignition coil. Since you have already replace the ignition switch, I would be looking for a broken wire. Almost all small engine ignition switches have the same terminal configuration on the rear, however the internal connections are all different and even if it looks the same, it in all probability isn't internally. Hope that this helps you better understand how it works.

 

[Lazy]

Re: How\'s An Ignition Switch Work?

Hi
What is the model number? I have a service manual that covers several wheel horse yard & garden tractors. maybe you could post the wiring diagram you have. When was the last time it worked?

Charlie.

 

[Soundguy]

Re: How\'s An Ignition Switch Work?

That switch in the off position either grounds the maggy output.. or opens the mag ground reference.. but I'll bet on the grounding the maggy.

Also.. choke to kill an engine will do just that... kill it over time. Choking to kill an engine causes fuel dilution of the oil.. washes the rings down and reduced lubrication on the cylinder walls for the last few revs... probably the only worse way to kill it would be to pour sand or water down the air intake /forums/images/graemlins/shocked.gif /forums/images/graemlins/crazy.gif

I workeed on lots antique engine where people thought the choke was the kill cable... oil turns to 0w0 pretty quickly...

Get a jumper wire to test out your faulty ignition switch.. ground the incoming wire that hits that position.. if it kills it.. there's your answer.. also.. the kill wire could be broke down near the maggy..

Soundguy

 

[MikePA]

Re: How\'s An Ignition Switch Work?

Attached is a schematic of the switch in the OFF position.

<font color="blue">RobS: I'd say you've got some corroded/worn contacts in the switch itself.</font>
Already replaced the switch. /forums/images/graemlins/grin.gif

<font color="blue">Junkman: Hope that this helps you better understand how it works.</font>
It does, thanks! The tractor, a Wheel Horse GT1600, has a magneto and no points.

<font color="blue">Lazy: When was the last time it worked?</font>
About 2 weeks ago.

<font color="blue">Soundguy:Also.. choke to kill an engine will do just that... kill it over time.</font>
I kinda thought this and told my wife the same when she said it was 'cute' that the little tractor didn't want to shut off, i.e., it wanted to keep on working. Come to think of it, this started happening when she decided to start cutting the grass again.

Where would I start looking for a broken wire, at the engine near the starter?

 

[_RaT_]

Re: How\'s An Ignition Switch Work?

Check your ground with an ohm meter at either G, M or A on the switch. When at the off position all three will be grounded. With a clip on ground and one on G,M, or A you should read a short or nearly 0 ohms. The case of the switch must be grounded to either the frame or a terminal provided to allow you to ground the switch in the event it is mounted in a plastic or other non conductive surface. What make is the engine? I have a Kohler that simply has a black wire along with other wires that connect in via a connector similar to what would be found on a trailer with 4 conductors in a flat connector. Good luck. Electrical problems can be a pain especially when they are intermittent.

 

[MikePA]

Re: How\'s An Ignition Switch Work?

<font color="blue"> What make is the engine? </font>
B & S IC Twin

 

[BB_TX]

Re: How\'s An Ignition Switch Work?

Mike - Everyone is right on with the grounding of the magneto. Looking at the schematic, when the switch is in the off position, the switch wire to the magneto is supposed to be grounded thru the switch. Also, you will note that if the PTO is engaged and the seat switch is made (seat unoccupied) it will also ground the mag to kill the engine. Does that work?
Check the magneto wire (the blue wire) thru all the locations shown on the schematic. Also there should be a ground wire to the switch. The diagram does not show what color that wire is. Find that wire and check it.

 

[MikePA]

Re: How\'s An Ignition Switch Work?

<font color="blue"> Also, you will note that if the PTO is engaged and the seat switch is made (seat unoccupied) it will also ground the mag to kill the engine. Does that work? </font>
That 'safety feature' has been bypassed for several years. /forums/images/graemlins/tongue.gif

<font color="blue"> Also there should be a ground wire to the switch. </font>
I 'think' this (grounding the switch) is working because when I tried to start the tractor when the switch was not mounted in the 'dash', nothing happened.

 

[BB_TX]

Re: How\'s An Ignition Switch Work?

Looking a little closer at the schematic, the switch case is grounded. The GT series has the seat ground wire to the switch.
However, from the switch operation box, it appears that in the start position the only connection is from the B (battery) to the S (starter) which would imply that ground at the switch is not needed to start. Hmmm?? /forums/images/graemlins/confused.gif

 

[Junkman]

Re: How\'s An Ignition Switch Work?

Check the blue wire for continuity from the flywheel (magneto located under the flywheel) to the ignition switch. The switch itself could be lacking a proper ground and/or the terminal on the rear of the switch could have corrosion on it and not be making proper contact. Since you have the problem with the new switch as with the old switch, I would reinstall the old switch so you know that it is correct for your application. You could also verify the new with the old by comparing the markings on the fiber board backing where the terminals come out of the switch. I would hate to think that you have compounded the problem with a wrong switch. If the old switch were defective and the new switch doesn't have the identical contact connections, this alone could be the problem. Never assume that a electrical product is the same because the external view is identical. The internals could be entirely different. If you have the wrong switch and have disposed of the old switch, then take the wiring schematic to a lawn mower shop. They can look up the proper part number and get it for you. Don't expect that they will have it in stock, because there are many different switch's and it isn't practical to stock them all. Depending on the popularity of the switch, it can cost between $6.00 and $26.00!!!!!!!! /forums/images/graemlins/frown.gif
I would simplify the entire testing procedure by removing the blue wire from the wire terminal end and grounding it directly. This can be done by using a very small flat bladed screwdriver to release the tang on the terminal in the plastic connector, or you could just use a piece of wire and "shove" it into the back of the terminal connector and touching the other end to the ground. Bare about 1" of wire at each end of the test wire for this beforehand for this operation. If the engine shuts down when you touch this wire to ground, it indicates a defective switch. If it doesn't, then it is a defective wire from the switch to the magneto. If it is the wire from the switch to the magneto, it will be quicker to just install a new wire bypassing the defective wire since this defective wire is bundled into the wire harness. If you find a break near the magneto, then splice, solder the connection and tape or shrink wrap the repair.

 

[Junkman]

Re: How\'s An Ignition Switch Work?

</font><font color="blue" class="small">( <font color="blue"> Also there should be a ground wire to the switch. </font>
I 'think' this (grounding the switch) is working because when I tried to start the tractor when the switch was not mounted in the 'dash', nothing happened. )</font>

/forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif The switch case is grounded and there should be a "star" washer between the switch and the dash board that "bites the metal" of the switch and the dash. Many times this washer is missing. It is available at most hardware stores as a "internal/external" star washer.

 

[MikePA]

Re: How\'s An Ignition Switch Work?

<font color="blue"> The switch case is grounded and there should be a "star" washer between the switch and the dash board that "bites the metal" of the switch and the dash. Many times this washer is missing. It is available at most hardware stores as a "internal/external" star washer. </font>
Yep, both the new switch and the old had one. The switch must be grounded OK since the tractor starts fine.

 

[MikePA]

Re: How\'s An Ignition Switch Work?

<font color="blue"> I would hate to think that you have compounded the problem with a wrong switch. </font>
I took the Service Manual for the tractor to the dealer and showed them the exploded parts diagram as well as the part number for the switch.

 

[MikePA]

Re: How\'s An Ignition Switch Work?

<font color="blue">I would simplify the entire testing procedure by removing the blue wire from the wire terminal end and grounding it directly. This can be done by using a very small flat bladed screwdriver to release the tang on the terminal in the plastic connector, or you could just use a piece of wire and "shove" it into the back of the terminal connector and touching the other end to the ground. Bare about 1" of wire at each end of the test wire for this beforehand for this operation. If the engine shuts down when you touch this wire to ground, it indicates a defective switch. If it doesn't, then it is a defective wire from the switch to the magneto. If it is the wire from the switch to the magneto, it will be quicker to just install a new wire bypassing the defective wire since this defective wire is bundled into the wire harness. If you find a break near the magneto, then splice, solder the connection and tape or shrink wrap the repair. </font>
I've printed this out and will try this when I get home from work. Thanks!

 

[MikePA]

Re: How\'s An Ignition Switch Work?

Got home from work and when I opened the hood to check the oil before cutting the grass, I noticed a black wire with a small, female spade connector. The wire was on top of the engine, near the throttle cable. Nearby was a male spade connector. So, I connected them. /forums/images/graemlins/grin.gif The engine now stops when the ignition switch is turned to Off. My guess is that my wife got a little too close to a hedge and a branch 'reached' in and pulled this wire off. The way the wire was positioned, this could happen when the tractor was moving forward. /forums/images/graemlins/shocked.gif It was a black wire, so I assume it was a ground and I think it was to the magneto? Not sure, but the important thing is we don't have to use the choke to kill the engine. Next step is to change the oil. Thanks to all for your input!

 

[Junkman]

Re: How\'s An Ignition Switch Work?

Check the tension of the connection and if it is loose, you could probably give it a little tweaking with a pair of needle nose pliers. Should have asked this question before purchasing the new ignition switch.

 

[Soundguy]

Re: How\'s An Ignition Switch Work?

It's nice to see the forum come thru!

Soundguy

 

[MikePA]

Re: How\'s An Ignition Switch Work?

<font color="blue"> Should have asked this question before purchasing the new ignition switch.</font>
Yep, should have. The 20 year old original switch was so corroded, it looked like the 'obvious' problem. Even though the old switch looked bad, it was still working. So, what something looked like on the surface didn't represent what was going on inside. By digging into the problem, with the assistance of the fine folks on TBN, I learned what was going on beneath the surface. The external appearance led to one conclusion, which was incorrect. /forums/images/graemlins/frown.gif

A $20.00 'Live and Learn' lesson. /forums/images/graemlins/smirk.gif