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Hello,

Hopefully this is the correct place for this question. I wasn't sure if this was meant for engine repairs or for repairs of units with small engines.

I have a John Deere D110 riding lawn mower that will not start and I'm running out of ideas for fixing it. The engine does not turn over, the lights don't turn on, just absolutely nothing. Here is the background. At the end of last season the mower refused to start. The battery was very old so I figured that was the issue and replaced the battery. It worked once more for the next cut, but would not start after that. I stored it for winter and started troubleshooting it at the beginning of this season. Here is what I have done so far.

I first assumed that it was the voltage regulator based on the fact that the mower cut once after changing the battery and wouldn't start afterwards. I assumed the regulator was not charging the battery and it discharged too much over that one cut to start the mower the next time. I got a battery charger and charged the battery (took about an hour), but there was no change. I then realized there was a system fuse (I'm pretty much learning as i'm going). It was in pretty bad shape and I couldn't get it to pass a continuity test so I replaced it and still no change.

I then did some research and based on what I've found the mower has 3 safety switches that all must be activated for the mower to start. One on the lever to activate the blade, one on the seat, and one on the brake. I went through and did a continuity test on all of those. I don't have a wiring diagram for the mower, but what I found was that there are 4 wires to each switch. Two of the wires are always connected and two pass the continuity test when that particular switch is engaged. This was the case for both the blade activation lever and the brake. Testing those was a struggle because I was having trouble getting the switches disconnected so I was able to do the tests by touching the metal inside of the ports on the plugs. The seat plug was different. I removed the seat from the mower and disconnected the plug and I was finding that all of the wires that plug into the seat are being read as connected (which seemed odd). The other thing that happened that I thought was odd was that when I was testing the brake switch I found that if my wife sat on the mower seat the brake switch would always read open, but if she stood up off the mower seat it read connected (when the brake was activated like you would if you were starting the mower).

Does any of this make sense to anyone or does anyone have any suggestions on what to do? Something seems out of place with the seat switch, however I would have assumed that if the wires were all connected it would not prevent the mower from starting?

Thanks
Nate
 

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Hi, Nate, and welcome to the forum. I'm sure we'll get you up and running here.

First, what is the voltage of your battery?

Second, is there any sound when turning the key? ( click? )

Third, and this is the good test. Put tractor in neutral, parking brake set, blades off. Take a short piece of wire and touch it to the battery side of the solenoid on one end and the other end to the small terminal on the solenoid (likely a purple wire connected there now). What is going to happen is the engine will immediately turn over if you have a) 12v to the solenoid, and b) a good ground connection.

Try those and let us know back.

Also, in my signature there is a link to a YouTube video that touches on some issues and will give you some pointers.
 

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Hi, Nate, and welcome to the forum. I'm sure we'll get you up and running here.

First, what is the voltage of your battery?

Second, is there any sound when turning the key? ( click? )

Third, and this is the good test. Put tractor in neutral, parking brake set, blades off. Take a short piece of wire and touch it to the battery side of the solenoid on one end and the other end to the small terminal on the solenoid (likely a purple wire connected there now). What is going to happen is the engine will immediately turn over if you have a) 12v to the solenoid, and b) a good ground connection.

Try those and let us know back.

Also, in my signature there is a link to a YouTube video that touches on some issues and will give you some pointers.
Hi Brad,

Thanks for responding to answer your first two questions. The mower has a 12V lead acid battery. When I turn the key nothing happens at all. No noise at all. The head lights don't work, just nothing at all.

For number 3, and this is probably going to sound dumb, but I don't think my mower has a neutral setting. I think its just off, on with headlights, on without headlights, and start. Do I need large gauge wire for this?

Another thing I thought was odd was when I finished charging the battery (charger said it was done) the voltage was about 12.6V. I thought a 12V lead acid typically charges to 13-13.5V?
 

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OH, it has a neutral setting (park, etc). Meaning, when the engine starts, you do not want it to take off down the street.

No, small wire OK, about 12 guage or so. Even house wire will work. You only need a wire about the size of the purple wire going to the solenoid.

One thing that could be happening is that maybe you have corroded batter posts. But, try the small wire to the small solenoid terminal first.
 

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A full charged battery will read 12.6 volts. 2.1 volts per cell.

I think the headlights on this model are powered by the stator when the engine is running??

Check the connection where the ground wire from the battery meets the frame.
 

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Taking a second shot at a response. Just typed out a longer one, but the forum logged me out and it got lost when I hit post.

I need to go get wire for the solenoid test you recommended. I have 16 gauge wire around the house for hobby electronics, but I unfortunately don't have anything with a larger gauge. I did put a voltmeter on the solenoid output that goes to the starter and the negative terminal of the battery and tried to start the mower and can confirm that no voltage is getting to the output of the solenoid. Not sure if that is at all helpful. I would have assumed that if the safety switches were broken the solenoid wouldn't do anything. Doing the short to bypass the solenoid would verify the starter is working right, but wouldn't help determine if the safety switches or the solenoid itself was the problem? Is that true? On the battery being too corroded the battery is pretty much new, but there is a small amount on the positive terminal. However, when the mower stopped working last fall the battery had been in the mower for about a week and there was no corrosion issue.

I don't entirely understand how the safety switches on the mower work (electrically). Is there a way electrically to verify on the mower when someone is sitting in the seat, the brake is activated, and the blades are disabled that all those switches are activated? As I said in my first post the one that really confuses me is why the brake switch is reading as open when someone is sitting in the seat and closed when the seat switch is not activated. That seems backwards as I would have assumed that all the switches should be closed when the mower starts.

For the ground to the frame. I know a continuity test from the battery negative terminal to the frame passes, but I can locate and check that ground just in case.
 

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One really quick test here. Take your volt meter, put 1 end on the frame/engine and 1 on the purple wire going to the small solenoid terminal. When you turn the key, do you get any reading?
 

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One really quick test here. Take your volt meter, put 1 end on the frame/engine and 1 on the purple wire going to the small solenoid terminal. When you turn the key, do you get any reading?
Brad,

There are two wires going to the solenoid one is black and one is brown. I did the test you suggested with the brown wire. It is on the top right of the solenoid. The layout, when looking from the front is (Top Left) black (Top Right) Brown (Bottom Left) To Starter (Bottom Right) From Battery. I sat in the seat and made sure the blade was off and the parking break was set and turned the key. I got no voltage on that input to the solenoid.

As a side note I also am fairly sure that all the safety switches are working properly. I found a wiring diagram that should be the same or extremely close to the D110. It looks like the PTO and the brake switches are connected together. I was able to measure continuity from the input to the first safety switch in the line all the way to the output of the last switch which I believe goes to that input you had me check on the solenoid. From the wiring diagram it looks like the seat safety switch works the opposite of the other switches. It is open when someone is sitting on the seat and is closed otherwise. I'm assuming when its closed it is shorting the electricity for the spark plug to the ground which causes the mower to sputter out when you stand up.

Nate
 

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My guess is that the black small wire goes to a ground, but that's a guess.

Might be such a thing that the switch is bad. Going to take some more testing with the multi-meter to verify tho. And a wiring diagram.
 

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I suggest you do as brad suggested. Remove the brown lead from the solenoid. Jumper to that tab from the battery positive. 16 gauge wire is ok for that test. I have had cases when I even had 12v on that brown wire and no cranking because of bad contact in the keyswitch so not enough current could flow. That jumper test can hopefully eliminate solenoid and starter and then you can start testing other things.
 

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