Huskee electrical issue in ignition circuit

kanmkkAugust 7, 2009

I have a Huskee lawn tractor/mower purchased new from TSC back in 2002. It's a hydrostatic drive with a 50" mower deck with a 23hp Briggs V-Twin. The MTD model number is 14AR807P131, S/N 1B051H10595. It's been a heck of a mower until last weekend. I had been mowing for several hours and needed to stop for refueling. After topping off the tank, the ignition key failed to get even a click from the solenoid or any sound from the starter. I had inherited this mower from my father, but did not get any kind of manual with it. Being a reasonable shade-tree mechanic, I started looking around for obvious problems. Battery is new with good connections. Poking around under the hood, while tracing wires, I discovered the fuse holder behind the instrument panel that serves the ignition circuit. The 20 amp fuse was blown. Before trying a new fuse, I examined most of the wiring harness to look for chafed or broken wires, or a loose ground connection somewhere. Everything seemed to be in good order. I removed the fuel tank to further examine the wiring behind the dash. I checked and cleaned all connections to the ignition switch, electric PTO (blade) switch, but still could not find anything amiss. I reassembled everything, reconnected the battery, and replaced the blown fuse with a new 20 amp. Settling into the seat, checking that the PTO was off, and stepping on the brake, I engaged the starter. Bingo, it took right off and ran perfect. I was uneasy about the blown fuse, however, and shut the ignition off to take one more look under the hood. Everything appeared OK, no smoke or burnt wiring smell. I tried starting it again, and nothing... I looked at the fuse holder, and the new fuse had blown. I fetched another new 20 amp fuse, but upon trying to install it, it blew the moment I plugged it into the fuse holder. One subsequent attempt produced the same result. I am baffled about why I was able to replace the original fuse without incident, and start the tractor normally. Now, I'm unable to introduce a new fuse to the holder without it blowing as soon as I touch it to the fuseholder contacts. Reviewing all of the wiring again reveals nothing obviously wrong. I don't want to start replacing safety switches, ignition switches, and solenoids without bouncing this problem off of some of the sage diagnosticians here who might be able to describe a methodical approach to isolating this electrical gremlin. I have downloaded the proper owners manual from MTD's web site. It has been helpful in all ways but one. It contains no wiring diagram. I scrounged around on the web and downloaded a Huskee tractor wiring diagram that appears to be close, but isn't an exact match. The way I understand MTD's policy, is that you have to buy a Technical Service Manual if you want a wiring diagram. I'm not ready to do that yet, but may be forced into it at some point. Any help would be very much appreciated.

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I am having the same problem with my agway MTD
18 hp.
Without the fuse you cannot start the motor.
Here is where I am up to:

1- In order to locate the short under intermittent
conditions I have stripped the wires on an
automobile backup bulb holder and plugged it into the
20 Amp fuse holder.

2- With the bulb installed I can start the mower
and see the charging current going to the battery
by the brightness of the bulb.

3- All of a sudden the bulb gets full brightness and
that is the short happening that would have taken out the
fuse. The motor keeps running and the brightness changes.

4- I am now down to moving all connections while it
is happening to find the location of the short.

5- The odd thing is if I pull on the ign switch harness
the bulb goes back to normal.

In order to cut the grass I figure I can leave the
bulb in and the mower will operate even with the
intermittent short.

    Bookmark   August 7, 2009 at 7:03AM
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***"I scrounged around on the web and downloaded a Huskee tractor wiring diagram that appears to be close, but isn't an exact match."***
Could you post a link to that wiring diagram?

    Bookmark   August 7, 2009 at 11:01AM
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here is an MTD 97 model that
has a 20 amp fuse.

May be similar.

Here is a link that might be useful:

    Bookmark   August 9, 2009 at 7:04AM
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Though I believe kanmkk is a transient, "one hit wonder", I will address the issue in hopes somebody will benefit from it. While the wiring diagram provided by corvetteguy might not be the "same" as for the Huskee in the OP, it is nonetheless "generic enough" to serve as a guide for hunting down a short circuit.
If I were doing the search, I would have my camera with me to shoot photos of the configuration of the wiring at each component and/or draw a sketch of the same so I would know exactly how the wires were routed, and how they connected to the component. When checking for a short, it is sometimes neccesary to disconnect a wiring harness section from one or more components so the harness can be brought out into the "open" for a close inspection. So you'll be able to return the harness to its previous location and with the proper routing, photos are great, and a sketch with notes is a good addition or substitute. I do both.
In looking for a short, you need to use all due safety precautions, you already know there is some kind of fault in the system, or you wouldn't be doing this. In regard to safety around the battery, you should disconnect the BATTERY NEGATIVE CABLE from the battery BEFORE you begin your search. This way, you will be working with an "inert" electrical system during the process of disconnecting/reconnecting wiring and/or electrical components. The BATTERY NEGATIVE CABLE can be reconnected at any time in the search if you want to check whether the fuse still "blows". On a typical small tractor battery, I use either a small vise grips plier, or an alligator type spring clamp to hold the BATTERY NEGATIVE CABLE in place on the battery post during the search instead of using the normal bolt and nut. The vise grips or alligator clamp allow you to "snatch" the cable away quickly if you need to.
To perform the checks by the following method, you will need an ohm meter, or a "continuity" tester. I prefer a continuity tester that has an audible beep or tone indicating continuity because you can use it in confined areas where reading the visual scale may be difficult. Continuity testers that use an LED indicator are good too. Some continuity testers feature both the audible and LED, some have both and an ohm meter as well. All continuity testers and ohm meters have an internal battery for power and should never be used to check continuity with the vehicle battery connected to the electrical system. OK, disconnect the battery negative cable and let's start looking.
If the system fues is blown or removed, install a good fuse of the proper Ampacity.
Step 1. Beginning at the key switch, disconnect the entire wiring harness from the switch if a single plug connector is used by the OEM. If individual terminals are used, disconnect the terminal that corresponds to the "B" terminal on the key switch in the furnished diagram. Isolating the key switch in this step will test for a short in the wiring between the fuse and the "B" terminal of the key switch. Connect one lead of the continuity tester to the DISCONNECTED battery negative CABLE, or any other good, clean, unpainted metal surface of the frame of tractor. Test the CONTINUITY TESTER by touching a few other surfaces that you know should be "continuous" with the ground system of the tractor. Essentially, if you are connected to a ground surface anywhere on the vehicle, the tester should show continuity whenever you touch any other ground surface of the vehicle. If the tester shows to be working and that the ground system of the vehicle is "sound", we can begin testing some wiring now. Leave one lead of the tester connected to ground and touch the other test lead end to the wire that connects to the "B" terminal of the key switch (touch the wire, not the key switch). If the tester indicates continuity, it means there is a short to ground somewhere in this circuit. To further check for the location of the short, go to the ammeter (if present) and disconnect both wires at the ammeter terminals. Touch the free lead of the continuity tester to either wire terminal on the ammeter, if the tester indicates continuity, the ammeter is shorted internally. If the ammeter shows to be good, touch the tester lead to either of the wires that you disconnected from the ammeter. If one of the wires shows continuity, that wire/circuit is shorted to ground and you will now have to trace that wire physically to locate the short. Logical places to look are where the wire harness bends around a metal surface edge or goes through a hole in a metal surface. If this test does not indicate a short, go to the next step.
Step 2. Go to the key switch. Make sure the key switch is in the OFF position. Connect one lead of the continuity tester to the GROUND TERMINAL of the key switch. On the wiring diagram provided, this terminal is "G". This terminal is where the key switch gets furnished with its connection to the vehicle ground, but we don't need for the switch to have an actual connection to ground to do the following tests, the key switch could be tested even if it were removed from the vehicle and placed on a workbench (non metallic bench).
First, check the tester by touching the two leads together (you always want to know that the tester works beforehand). With one test lead on "G" terminal, touch the other lead to the "M" terminal on the switch. You SHOULD HAVE continuity between the "G" & "M" terminals at this time because continuity between those two terminals is what "kills" the ignition spark to stop the engine. Leaving one test lead connected to the "G" terminal, touch the other lead to the "B" terminal of the switch. You should NOT HAVE continuity between these two terminals. If you DO HAVE continuity, the key switch is shorted to ground internally. I expect a short to be found in Step 1 or Step 2 if the fuse was blowing with the key switch in the OFF position. If this test does not reveal a short, we will go to Step 3.
(to be posted later if the first two tests sessions do not locate a short).

    Bookmark   August 9, 2009 at 2:16PM
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Hello, this is your "transient, one-hit wonder", here. I very much appreciate the excellent, detailed advice, and the willingness to assist me in solving my Huskee electrical problem. I apologize for having been away from the forum while traveling on business. As for the link to the wiring diagram requested above, I printed it down from the MTD website, and since Windows truncates the lengthy site address in print form, I can't reconstruct the link without going through the dozens of MTD models/years. I did scan it to PDF and can email it to anyone who might be interested. I don't believe it's as good as the one posted by mownie, however. I have the tools and equipment, and most of the skills necessary to follow some of the advice provided above. Since my tractor is located at some suburban property I own, I will have to wait until the weekend to apply some of the recommendations. I promise to report my findings, and will certainly trumpet any successes, for the benefit of other readers who may be following this thread, and experiencing a similar problem. As a working-Dad with two small children, I can't promise I will be logged on to this forum every night in the meantime, however. I'm sure that you understand. I really do appreciate the help, and I value the knowledge of the subject matter experts who follow this forum. I would not have posted a detailed message, nor would I have wasted anyone's time here, if I were not interested in finding a solution, and a logical method of pursuit. Thanks for not being judgmental in the future -kanmkk

    Bookmark   August 11, 2009 at 12:45AM
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If you want to, you can send the PDF to me as an e-mail attachment. Sorry if I sounded judgemental. You just wouldn't believe the number of one hitters, fly by nighters, and other such hit and run people that drive by and toss a thread in here. The members who have been here a while know all too well what I am referring to. Send me that schematic and I'll have a look.

    Bookmark   August 11, 2009 at 1:36AM
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Regarding the wiring diagram furnised by corvetteguy:
Below is a "Continuity chart" to illustrate which terminals of the Key Switch share continuity provided by the contacts of the switch for each of the 4 possible positions of the Key Switch (OFF, RUN/LIGHTS, RUN (no lights), and START.
Notice that the HEADLIGHTS circuit is powered by AC from a separate, dedicated winding in the alternator stator assembly (that's why I showed the continuity in green for the headlights terminals). The HEADLIGHTS circuit is completely separate from the DC circuits controlled by the KEY SWITCH and DO NOT ever share continuity "one with the other". For this reason, determine whether your vehicle electrical system uses AC or DC to power the HEADLIGHTS before you attempt to check for voltage if you have a problem with headlights. Here's a "non invasive" way you can tell. IF, you can turn on the headlights WITHOUT running the engine (but you might have to turn the KEY SWITCH to "RUN"), your headlights are powered by the DC electrical system. IF your headlights will only light up when the engine is actually running, and burn dimly at idle RPM and brightly at higher RPM.......your headlights are powered by a separate, dedicated portion of the alternator. Your specific vehicle might feature a separate headlights control switch from the KEY SWITCH no matter the type of power that feeds the headlights circuit.
Further FYI, the "L" terminal on this switch would also serve as the "ACCESSORY" terminal for any 12VDC accessories that might be featured on the vehicle, including a "carburetor fuel solenoid".

    Bookmark   August 15, 2009 at 1:05PM
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Thanks to corvetteguy and mownie for your help and recommendations towards helping me bring my Huskee tractor back to life. I can report that after last Saturday's diagnostics session, I am back in the saddle, and the Huskee is starting normally, and no longer blowing fuses. After running the diagnostics recommended by the two contributors listed above, I found no errant grounding in any of the wiring harness, and subsequently turned my attention to the components. Since I suspected that the ignition switch was not behaving normally, I started there first. It was a fortunate choice of starting points. After disassembling the seven-contact switch, as mownie describes above, I found the copper circular contacts inside in poor condition, and burnt from arcing. The contact buttons on the matching backplate were also in rough condition, no doubt not aided by the dirt/grime caked in the contact areas. Finding a switch on a Saturday afternoon appeared as though it would be a challenge. A trip to the nearby John Deere dealer produced a part number for an identical switch, but unfortunately not in inventory. Tractor Supply was the next stop, same result. The folks at Tractor Supply suggested that I stop by the Sears Parts & Repair store in a nearby strip mall. There I found a bin full of these identical switches. Fourteen dollars and thirty minutes later, the tractor was purring like a kitten. The fact that there were a bin full of these switches at Sears tells me that this is a frequently-replaced part, typical of many MTD, and similar lawn tractor models. I am pleased with the results, and I'm even more pleased with the help I have received from the contributors to this forum. Thank you very, very much!

    Bookmark   August 18, 2009 at 11:25PM
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I have added a few photos of the offending switch and the burnt contents therein. If your tractor has one of these and you're experiencing similar trouble, this may be a place to look. It's a cheap fix, too.

    Bookmark   August 19, 2009 at 12:12AM
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Mownie has asked me for a clearer picture of the backplate of the switch showing all of the alphanumeric tags for the harness connection blades. I'm also including an annotated photo of the interior side of the backplate that shows the contact buttons, burnt and otherwise, with tag labels for the corresponding harness blades. One tab on the backplate is unlabled, as far as I can tell. It's the one in the upper middle. I've annotated it with a question mark. I'm certain that mownie can identify it. He may choose to post an analysis as a followup to this thread. Perhaps these pix might be helpful to others. - kanmkk

    Bookmark   August 19, 2009 at 10:10PM
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