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Hello. I have a no start issue with my Husqvarna YTH21K46. I've read tons of threads on this board but haven't come across this exact situation. Maybe my google-fu just isn't that strong. I have been following Rivets' EXCELLENT troubleshooting steps but am still hung up.

I've confirmed the battery is charged (12.8V on my multi-meter) and all connections are good/clean/tight. I'm reading just about the same voltage at the starter solenoid on the large terminal (it's a 4 post solenoid, for reference). I'm also getting power to the small white wire when I turn the key - THE FIRST TIME. If I turn the key a second time I get nothing. I'm using a test light for this and the first time I turn the key it triggers the light but then nothing on subsequent tests. I hear a tiny "click" but nothing like what you hear with a dead battery, just a faint solitary "click". Also, I've noticed that the digital hour read-out on the dash will light up the first time but not the second time I turn the key. If I disconnect the battery and wait a bit, I can repeat these steps but not without disconnecting and waiting. I also happened to have a spare ignition switch and tried both but get the same results.

For some background, the mower has been covered but outside for the past year or so and was dead. Wife said I needed to either fix it or sell it. I replaced the starter solenoid but that was my bad diagnosis and didn't fix the problem. After more studying on here, I traced it down to the starter. I put in a new one, sprayed some starter fluid, and got it running in no time. Mice had infested this thing pretty bad though. They didn't build a condo - they built a full on amusement park under the engine cover. Needless to say, this thing was nasty and it stunk... real bad. I gave it a deep, deep cleaning and this is where I went wrong because after the bath, oil change, and new fuel filter it won't start now. I know water and electronics don't mix but I couldn't sit on this thing with that mouse smell and had water all over this thing. I've checked all the wires and connections but can't see anywhere that the mice ate any wiring but perhaps I'm still missing a break/short.

So the spa day definitely killed something, I just can't figure out what. I've gone through all connectors I could find, opened them up, sprayed some WD40 in there and let them dry out a bit before re-connecting. I've also replaced the fuse (not blown, just as a precaution). Now instead of having a nasty dead mower in the backyard I've got a clean dead mower in the driveway. Any help y'all can provide would be greatly appreciated!

See wiring schematic page 27. Headlights work with key on? Check ignition switch plug at backside of dash by removing plug & checking switch terminals & plug for corrosion etc. Purchase a tube of silicone dielectric & apply at all electrical connections including spark plug boots. If it will not start remove battery & take to auto parts store to be load tested at no cost to you. Let us know how it goes, thanks, Mark

Sounds really like the fuse
All the power to the mower apart from the clutch runs through a single fuse
The wires can break at the terminal crimp, the sockets corrode etc.
Did you fit the solenoid properly ?
Usually the above mentioned power feed wire is connected to the battery lead on the solenoid.
A bad connection between the battery straps ( either end ) will also cause your problem.

A year outside in the weather (under a tarp simply intensifies the humidity) followed by a bath. Smells like a gross case of terminal corrosion. It's most probably on several contact points, not simply one. That's why it's hard to find and/or diagnose. Look at these 3 places....

• Inside the ignition switch where you can't get. You can try spray "Contact Cleaner" into the switch, but you'll probably end up replacing the switch. Or one of the external terminals on the switch itself.
• One of the starter interlock switches or terminals
• Fuses (if you have them)

They make several brands of ointment electricians use to break through terminal oxidation and corrosion. As you unplug each terminal, you can wipe a very small portion of this stuff on each male connector terminal, and then re-plug the wire. The stuff I use is called No-Ox-Id by Sanchem, which is sold on Amazon. From time to time they offer a tiny tube for $2, which is enough to treat 10 mowers. It just takes a tiny bit. Then they have larger tubs which are over-kill for your needs. This stuff eliminates the corrosion and keeps it from returning later on.



Hope this helps.

Sounds like a poor connection/ corroded terminals at the ground or positive cable, and maybe keyswitch. The tiny click is likely the fuel shutoff solenoid.

Please post the voltage results to each of the steps in my troubleshooting procedure. Then we can have a better idea on how you should proceed.

mechanic mark said:

https://www.mowersdirect.com/manuals/YTH21K46_manual.pdf

See wiring schematic page 27. Headlights work with key on? Check ignition switch plug at backside of dash by removing plug & checking switch terminals & plug for corrosion etc. Purchase a tube of silicone dielectric & apply at all electrical connections including spark plug boots. If it will not start remove battery & take to auto parts store to be load tested at no cost to you. Let us know how it goes, thanks, Mark

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Hey Mark,

Thanks for taking the time to reply. The headlights don't turn on with the key but I think that it's just because the bulbs are old and non-functional. I put a test light on the connection point where the wire running along the chassis connects into the splitter that goes to each bulb and when I turned the key on the test light lit up - so I know power is at least getting to the front end via the key. Again though, once I tried to start the motor I heard the faint "click" and then couldn't get the test light to trigger any more.

I did take the ignition switch apart again to clean it all down. I actually have a spare ignition switch and tried both but no luck. They are both in "new" condition and no corrosion on them (the male parts) or the female parts in the harness under the dash.

Good call on the dielectric grease. I don't have any on hand but will pick some up when I go get the battery checked out. If I'm getting 12.8V at the battery and through to the first big terminal on the solenoid, could the battery still be bad?

dana3132 said:

Good call on the dielectric grease. I don't have any on hand but will pick some up when I go get the battery checked out. If I'm getting 12.8V at the battery and through to the first big terminal on the solenoid, could the battery still be bad?

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Dielectric grease is great on new equipment, before trouble starts. But since it only stops new water from causing new corrosion it's not great. Probably work, but not the best. Look up the word "dielectric" in the dictionary and you'll start to understand.

Born2Mow said:

Dielectric grease is great on new equipment, before trouble starts. But since it only stops new water from causing new corrosion it's not great. Probably work, but not the best. Look up the word "dielectric" in the dictionary and you'll start to understand.

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Thanks! I just saw your post too and am looking into the No-Ox-Id too

I am not sure if you replaced the battery but if you did not, yes you can appear to charge a battery that's bad and it will show proper voltage until you put a load on it and it drops to a very low value. A simple test of this is to put your meter (not the test light) right on the battery terminals. Turn the ignition switch on and off. Then repeat. Does the battery voltage stay over 12 for the entire sequence, or do you see a dramatic reduction when you hit the ignition the first time? If so then it's new battery time.

As a side note, I run into this all the time when servicing battery backup sump pumps(particularly the 'dumb' ones that don't cycle the backup DC pump and hence the battery). A battery that would normally last 4-5 years in a car or boat can go bad in a year or so. You pull the charger off and measure the voltage and sure enough it's 12+ volts, but put a load on it and it drops to a low value >>> battery is shot. That's because the battery is just sitting there 24/7/365 and never gets cycled. Shortens battery life dramatically.

Good luck!

Four terminal solenoid, so you should have 2 heavy wires (one from battery, one going to starter) and two smaller wires, one should go to ground (does it). The other wire is part of a series circuit that runs from the battery, ignition switch, seat switch and PTO switch and possibly a switch on the brake. These switches keep you from starting out of the seat, with the PTO engaged and with the brake off, any one of them not working or a wiring fault will keep the solenoid from engaging. If you run a wire from battery positive to the non-grounded side of the solenoid coil, does the solenoid try to engage?

BTW - I had an intermittent start problem on my Bad Boy mower, turned out the bolt on the positive battery terminal had loosened up, made good enough connection to run the mower, but didn’t always pass enough current to crank the starter.

Rivets said:

Please post the voltage results to each of the steps in my troubleshooting procedure. Then we can have a better idea on how you should proceed.

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Hey Rivets, thanks for offering to help. Here's how far I've gotten, following your 6 recommended steps I've seen in other posts:

1. Confirmed fuse is good and clean. Scrubbed and cleaned the connections at the battery (looked pretty good, but disconnected and scrubbed anyway). Voltage at battery, while disconnected, is 12.71
2. Voltage at one of the large terminals on the starter solenoid reads 12.71
3. Voltage at the small white wire on the starter solenoid reads 12.6 when I turned the key. The other small wire never read anything on the multimeter but I think that's expected. I tried tracing that wire down to the chassis to ensure a good ground but due to where the wire is routed behind the gas tank and the wire shroud, I couldn't follow it all the way. I also measured the voltage at the fuse (with the fuse removed) and it read as 12.69
4. No power read at all on the other large terminal of the starter solenoid when the key was turned. I ensured the fuse was seated and that the small white and black wires were put back on tight on the solenoid and that the solenoid had a good clean connection to the chassis.

I also had the multimeter hooked to the battery while trying to start the mower and didn't see much of a drop at all. I have not had a chance to have a parts store test the battery yet.

The solenoid is fairly new (about 6 months old with less than 10 starts) but I'm suspecting it's the culprit. Looking forward to hearing your thoughts. Thanks again.

If you went after it with a power washer or high pressure garden hose, it's likely that everything that can get wet got wet -- including everything under the flywheel. That's where the alternator is. First thing I'd do is pull the flywheel. It wouldn't surprise me if the problem presented itself pretty quickly after that.

just a guess, but having mice making a home in it for a while, it sounds like they may have partially chewed threw a wire somewhere in the harness. most of runs under the hood up closer to the dash. That is where I would start.

the small wire that you are getting power to when you turn the switch on runs through your safety switches, typically you have a brake switch, seat switch, and a pto switch if it is a lever system. If it has a clutch that operates the pto then the switch could be bad. to check it remove it look at it one side will have comm three times on one side. the number of terminals may vary. check for continuity from common to the out side terminals with the switch in the off position (should read 0) the pull the switch out and check from common to the inside terminals. should also read 0. make sure to check the terminals across from the common not at an angle.

No voltage on the large terminal going to the starter when you turn the key, and no clicking of the solenoid means you have a problem with power going through the coil circuit of the solenoid. Disconnect the small wire going from the solenoid to ground and measure the resistance through this wire to a good ground. It should read 0 or very low. If it doesn’t you have a bad ground wire, which is simple to replace. You can also just take a light jump lead and connect it between the ground terminal on the solenoid to a good ground. Tell us if anything changes. Tbone, charging system has nothing to do with the starting system.

Tbone0106 said:

If you went after it with a power washer or high pressure garden hose, it's likely that everything that can get wet got wet -- including everything under the flywheel. That's where the alternator is. First thing I'd do is pull the flywheel. It wouldn't surprise me if the problem presented itself pretty quickly after that.

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Just used a regular garden hose and kept the spray mostly "down" but definitely got more water in places than a normal wash would.

Measure the battery voltage from positive to negative on the battery and then from positive to chassis ground. I have seen the negative wire not making good contact at the ground connection. If you have 12 volts or so between the terminals on the battery but not when you measure between positive on the battery and chassis ground you have a bad connection on the ground attachment, usually caused by rust and corrosion. Remove and clean then treat so it won't happen again. If the voltage readings are all okay you probably have a problem with the PTO or mower engagement switch (depending on whether you have an electric clutch or lever for deck engagement) or the break interlock switch. On the solenoid the black wire(s) are ground so should not read any voltage. The other one, sometimes purple, carries 12 volts and goes through the interlock switches. Sometimes the switches become physically loose in their bracket or there could be a bad connection at the plug.

Rivets said:

No voltage on the large terminal going to the starter when you turn the key, and no clicking of the solenoid means you have a problem with power going through the coil circuit of the solenoid. Disconnect the small wire going from the solenoid to ground and measure the resistance through this wire to a good ground. It should read 0 or very low. If it doesn’t you have a bad ground wire, which is simple to replace. You can also just take a light jump lead and connect it between the ground terminal on the solenoid to a good ground. Tell us if anything changes. Tbone, charging system has nothing to do with the starting system.

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Disconnected the small wire from solenoid to ground and got 0 resistance.

I did change out the starter solenoid just as a precaution (scrubbed everything down to ensure good ground too) but still not starting. It is making a louder clicking noise now when I turn the key and it will last for about 2 or 3 seconds before stopping. Same other behavior has been noticed in that it will not repeat this behavior. I can turn the key once and get the hour gauge to turn on and when I turn the key I get the clicking but not twice in a row. Disconnect the battery and let it sit for a while and the cycle repeats.

Just to eliminate a possible cause, disconnect the ground cable froze the framer or engine, where ever it is connected. If you can measure the resistance through this cable, must be less than 5 Ohms. Clean the terminal and the frame down to bare metal, no paint and reconnect. We want to make sure that this connection is not a problem. Second, if you have materials ( 2 wire terminals and a short piece of braided wire) make yourself a jump lead to temporarily ground the solenoid. You can connect this lead to any good ground. When you install and test this it will tell us if current is going through thr primary circuit of the solenoid, you should hear a loud clipping sound.

Telesis said:

I am not sure if you replaced the battery but if you did not, yes you can appear to charge a battery that's bad and it will show proper voltage until you put a load on it and it drops to a very low value. A simple test of this is to put your meter (not the test light) right on the battery terminals. Turn the ignition switch on and off. Then repeat. Does the battery voltage stay over 12 for the entire sequence, or do you see a dramatic reduction when you hit the ignition the first time? If so then it's new battery time.

As a side note, I run into this all the time when servicing battery backup sump pumps(particularly the 'dumb' ones that don't cycle the backup DC pump and hence the battery). A battery that would normally last 4-5 years in a car or boat can go bad in a year or so. You pull the charger off and measure the voltage and sure enough it's 12+ volts, but put a load on it and it drops to a low value >>> battery is shot. That's because the battery is just sitting there 24/7/365 and never gets cycled. Shortens battery life dramatically.

Good luck!

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A better way to make this test is to monitor the voltage at the B+ terminal and then the Motor terminal on the starter both in key off and key on. If at least 9 volts is present on key on, the starter is drawing current and should do it's job. If no voltage hits the motor terminal of 9volts or more but is present at B+ at the solenoid and the small control wire then the solenoid is not making motor terminals live. If 12 or battery no load voltage at solenoid b+ with key on but nothing on control wire then interlocks and wiring and ignition switch is your next troubleshooting loop. If mice have damaged and corrosion has set in then a way to simply bypass all interlocks and also make all safety features defeated but prove root cause is to find the start terminal wire on switch wiring and feed it directly to the control small terminal on the solenoid. This bypasses safety and will crank if battery and switch and starter and related connections are good. In your very first post you mentioned that on second attempt to start nothing would happen until waiting. This suggested 1) a auto reset circuit breaker or 2) corrosion, or 3) battery capacity. Battery capacity with a new battery should be no longer an issue if the new battery is good - which in my shop has found 2 bad batteries right of the gate, so to know this is not an issue, under an attempted load the battery voltage will always drop some, how much is important. This is where the highest load is the starter and a normal design is the battery should sustain such load and droop to no lower than 9volts. All other loads should be far less and hardly impact voltage any lower than say 10.5 or 11 volts. Good luck.

Rivets said:

Just to eliminate a possible cause, disconnect the ground cable froze the framer or engine, where ever it is connected. If you can measure the resistance through this cable, must be less than 5 Ohms. Clean the terminal and the frame down to bare metal, no paint and reconnect. We want to make sure that this connection is not a problem. Second, if you have materials ( 2 wire terminals and a short piece of braided wire) make yourself a jump lead to temporarily ground the solenoid. You can connect this lead to any good ground. When you install and test this it will tell us if current is going through thr primary circuit of the solenoid, you should hear a loud clipping sound.

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OK - we're back in business. Still left scratching my head a bit but here's what happened.

First, I tested resistance through the battery's ground cable to the chassis and got 0 resistance. I took the cable off entirely and tested it by itself - again, 0 resistance. It is bolted down just above the rear tire and the bolt and ring looked pristine. Regardless, I sprayed it down with some WD-40 and hit it with a wire brush (the ring, the bolt, and the connection point).

Second, I made a jump lead to ground the solenoid. Undid the existing small ground wire (which was always reading 0 resistance, so I felt like I already had a good ground) and put my jump cable on and then connected to a bolt on the engine to ground it.

I hopped on the mower and it started up. Ran it for a while, turned it off, started up again. I undid my jump lead from the solenoid ground and hooked the original wire up - and it started. So it's got to have been a bad ground connection from the battery down to the frame. It looked really good to me with no corrosion but who knows. Should have tested after each step to know for sure but at the end of the day, I'm back up and running - finally.

Thank you Rivets for taking the time to read all these messages and guide me to a solution.

Not a problem, I got lucky this time. Glad to hear you have it running.