Free MTD tractor

jimengeleSeptember 12, 2013

So I have this tractor that I can have if I can fix it. I discussed the transmission in a previous thread.

Some time ago, the previous owner informed me there was a lot of damage done to the wiring by a mouse or rat. They took it into a shop who informed her they replaced the ignition switch, the wiring harness, and performed other routine maintenance duties, $300. The machine still occasionally stalled out on her and she gave it away for free to me.

I checked it out and determined that the ignition switch had not been replaced, the wiring harness had been removed and replaced with direct wiring. All safety switches had been disconnected and one safety switch was missing completely (the blade engage lever). The headlights were disconnected, the battery recharge circuit was disconnected. The wires were gone. Just the very basic wiring was intact. I discovered that the wire to the anti-afterfire solenoid was very loose and that was what was causing the occasional stall.

For now, I would like to rewire the battery recharge circuit and I wanted to know what the best way to do this is, what type of wire (18 gauge?). I have determined the alternator is a split 3 amp/5 amp (yellow wire, red wire). I don't know yet if there is a diode on the yellow wire but if there isn't, what type of diode should I use? I know that this 3 amp line recharge circuit could be wired directly back to the battery but I was thinking of reconnecting it through the ammeter. For that matter, should I connect it to the battery through the ignition switch? There is a terminal that connects when it's in the 'on' position. Should I install a fuse in this circuit? Where is the best place for the fuse? I'd eventually like to hook up the lights as well, perhaps through the ignition switch to the battery as well. Of course, I'd like to hook up the safety switches as well, one thing at a time.

Ace special edition
Tecumseh Enduro OHV16

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might just be better off going with OEM harnesses. Try the link below and enter the model number of your machine > select the electrical category> select harness(es) needed.

Here is a link that might be useful: mtd parts

    Bookmark   September 12, 2013 at 8:45PM
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Ya, I looked at that and there are a few different wiring harnesses available with or without lights, various differences for the type of engine, etc. All for around $100. Or I could just run a wire directly to the battery. I'm curious if anyone thinks it's wise to run it through the ignition switch 'on' position.

    Bookmark   September 13, 2013 at 2:27PM
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So here is my plan:

I will connect a wire 18 gauge to the red wire 3 amp wire coming off the alternator with diode. This wire will connect to the battery wire on the ignition switch. This battery wire will connect to the ammeter in the dash which will then continue through a 25 amp fuse and then to the solenoid under the seat which connects to the battery.

This configuration should allow the ammeter to be in series and will show charge/discharge as the case may be correct?

When the ignition switch is in the 'on' position the battery terminal of the switch is continuous through two other spades on the back of the switch, one that goes to the anti-afterfire solenoid and one that currently has nothing on it but I might put the headlights if I feel like it.

My question is this: Should I connect the alternator charging wire directly to the battery wire coming out of the ignition switch or, should I connect the alternator charging wire to one of the other spades so that when the switch is turned off that circuit is disconnected (also, when in 'starting' position, the alternator will be disconnected there as well). I'm not sure if any of this matters. I might be over thinking.

    Bookmark   September 25, 2013 at 10:48PM
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Maybe this Craftsman schematic will give you some ideas?

Page 33/60

This has the light switch as part of the key switch.
IF your tractor has a separate light switch, ignore the A 2 & L terminals.

This post was edited by bill_kapaun on Thu, Sep 26, 13 at 15:45

    Bookmark   September 26, 2013 at 3:41PM
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That helps a lot. MTD schematics suck.

I wanted to connect the charging circuit to the spade that has the afterfire solenoid wire on it and this diagram confirms that would be fine. It confirms the position of the ammeter in my circuit as well.

I do have a separate light switch so that will be no problem.

I also would like to install a voltmeter which I think I can do to the extra spade in the 'on' position.

thank you, very helpful.

    Bookmark   September 26, 2013 at 6:30PM
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You could just tie the volt meter into the same circuit as the fuel solenoid. That way you know it's OFF when the key is OFF.

    Bookmark   September 26, 2013 at 8:05PM
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Ok, I got the lights and the recharging circuit and ammeter all hooked up and running properly. I had been thinking of powering the lights off the battery through the ignition switch but in the end it makes more sense to use the alternator instead. I placed a 6 amp fuse in the circuit as well. I used 18 gauge wire from radio shack along with crimp on connectors. I cut off the existing double connector on the 3/5 split coming off the alternator so I could use the radio shack double connector.
The battery wire coming from the solenoid to the ignition switch was 16 gauge with an automotive blade style 25 amp fuse. This seems wrong to me, I don't think 16 gauge can handle 25 amps before burning up? I'd like some input on that. After the fuse, I cut the wire and hooked it up to the ammeter and on to the ignition switch. I connected the charging circuit to the wire that goes to the afterfire solenoid. Now the ammeter works as advertised. I had put a pin in the wire upstream of the diode and checked the resistance across the diode. I get a little resistance one way and when I switch the leads I get no reading at all. With the engine running the ammeter shows it charging and when the starter is turning it shows it discharging.
I cut the lawn and what used to take me 3/4 hour with a push mower now takes about 1/4 hour, nice. I need a dump trailer now to make it really useful. I'd like to close off the deck and mulch and/or I'd like to install a bagger. I also plan on installing a voltmeter ($7.50 harbor freight) and I have a leaky front tire that needs an inner tube.

    Bookmark   September 29, 2013 at 6:04PM
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You could use a much lighter fuse.
You shouldn't have more than starter solenoid + fuel solenoid current going through it.

I think since you have an ammeter, a volt meter isn't really that useful. It's charging or not.

    Bookmark   September 29, 2013 at 6:26PM
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Well, you have to look at it like this.....there is no component on the tractor that is going to impose a continuous load of anything near to 25 amp. So the long term/long time continuous load is going to be more in the range of 3 amps or less.
However, a direct short to ground is capable of imposing a load that in theory might exceed 50 amps, which will make the 25 amp fuse pop like a camera flash. The high amp load will not exist long enough for the 16 gauge wire to even feel warm, let alone do any harm.
But, a continuous load of 20 amps will ultimately heat up the 16 gauge wire until the insulation fails, at which point the 25 amp fuse will fail........but only if the failure point is located between the fuse and the load. If the failure point is located between the fuse and the battery + connection point, be prepared to dial 911, because the 16 gauge wire is about to turn red hot.
Personally, if I were going to make any alterations (to err on the side of caution) I would use 12 gauge wire and a 20 amp fuse if no electric PTO clutch is part of the picture (25 amp if electric PTO).
But I would also relocate the fuse holder so that there is a very short run of wire from where the circuit begins, say.....not over about 6". That way, the chances of a short ever developing that the fuse can't protect against.....are greatly reduced (I stop "short" of saying ELIMINATED).
Realistically speaking, the odds of the 16 gauge wire ever causing an issue are very small.
If there was a plethora of fires and failures due to industry using small gauge wires that seem to defy logic, then the industry would have been forced long ago to upsize their wires. Truth is, the 16 gauge wire is adequate for a 3 amp or 5 amp charging system where there are no large consumption components featured on the machine.
And if it were me, I would have said "I had a leaky front tire that I put some Slime into." ^:)

    Bookmark   September 29, 2013 at 6:56PM
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Ha! I know, my friend suggested I put slime in the tire but I thought an inner tube is a more permanent solution and I won't have to deal with the whole 'bead seal is broken' issue.

So, I think I'll cut out the old fuse holder (the cap is missing and the contacts are bent and not making a good connection). It's maybe a foot down wire from the solenoid as it is but I will move it a little closer. There is a crimp on connection in between that I can eliminate as well. And, put in a 20 amp fuse? Maybe I should put a 10 amp fuse in and see how long it lasts?

    Bookmark   September 29, 2013 at 7:14PM
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10 amp might be stretching it a bit, I can't say for certain how much load the engagement of the starter SOLENOID imposes.
It might exceed 10 amp, but if it does, it's only gonna blow the fuse.
I ran into this back in the 1990's at work. We were having problems with an entire group of forklifts of a certain brand and model.
The issue was that after a forklift of that model had accumulated about 6,000 hours, sometimes when the key was turned to start, the solenoid would not activate.
Extensive diagnosis finally determined that there were 20 connections in the cranking circuit between the key switch and the solenoid (due to wiring techniques and safety devices). It turned out that a little resistance here and a little more here and a little more over there added up to quite a loss of ooomph in the circuit that is supposed to activate the solenoid and then the starter.
During that diagnostic process we found out that the starter solenoid itself would draw a 65 amp load. This was accomplished with a 14 gauge wire fed from a 40 amp FUSIBLE LINK.
The only reason it worked at all is because of the duration of the 65 amp draw was so brief. After the initial surge of 65 amp to move the solenoid, the continuous draw of the solenoid was only about 20 amp.
I have never tested a solenoid of the size we deal with on OPE, so I can't say with any authority what it would draw as the initial amp load.
Try a 10 and if it blows go to 15, or 20. I have seen plenty of tractors with 20 amp fuses, but I've also seen some with 30 amp.

This post was edited by mownie on Sun, Sep 29, 13 at 21:44

    Bookmark   September 29, 2013 at 9:41PM
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You're right, the MTD wiring diagram they put in the manuals aren't the easiest to read.
Let me offer this enhanced wiring diagram for the MTD-600 chassis, taken from the manual and made easier to read via Windows Paint.

Double yur money back guarantee if it doesn't help, haha.

    Bookmark   April 7, 2014 at 1:36AM
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