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I have a mid 2000s Craftsman mower made by Husqvarna. It has a brand new 20 hp Briggs V-twin engine that I installed last year. It was running when I drove it into the shed for the winter. I tried to start it today and there was nothing, no click no crank, no anything. I assumed it was a dead battery, so I swapped it out for a known good battery and had the same result. So now I apparently am stuck with diagnosing an electrical fault.

My question is this: are the safety interlock switches on these mowers normally open or normally closed? in other words when I check them, am I looking for them to give continuity or not when they are activated? Thanks in advance for any help.

This is the procedure I use to diagnose those problems. If you can’t find it report back with you finds for each step.

Electrical problems can be very easy or very difficult, depending on four things.
1. How well you understand basic electricity.
2. What tools you have and know how to use.
3. How well you follow directions.
4. You don't overlook or assume anything and verify everything.

Remember we cannot see what you are doing. You are our eyes, ears and fingers in solving this problem. You must be as accurate as you can when you report back. The two basic tools we will ask you to use are a test light and a multi-meter. If you have an assistant when going through these tests it would be very helpful. These steps work the best when done in order, so please don't jump around. Now let's solve this problem.
First, check the fuse(s), check battery connections for corrosion (clean if necessary) and voltage - above 12.5 volts should be good. Check and make sure the chassis ground is clean and tight.
Second, check for power from the battery to one of the large terminals on the solenoid. One of the wires is connected directly to the battery and has power all the time so one of the large terminals should light a test light or show 12 volts on a meter at all times.
Third, check for power at the small terminal of the solenoid while depressing the clutch/brake pedal and holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch). If your solenoid is a four wire solenoid, check both small wire terminals as one is ground and the other is power from the ignition switch. If your solenoid is a three wire solenoid, make sure the solenoid body is not corroded where it bolts to the chassis of the mower as this is your ground path back to the battery. If in doubt, remove the solenoid and clean the mounting area down to bare metal. If there is no power to the small terminal then your problem is most likely a safety switch, ignition switch or in the wiring.
Fourth, check for power on the other large terminal of the solenoid while holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch).
Fifth, check for power at the starter while holding the key in the start position (assistant again).
Sixth, check your ground circuit back to the battery.
After you have gone through each of the above steps, let us know what happened when you did each step. At that point we will have great info to tell you how to proceed. Remember you are our eyes, ears, and fingers, so please be as accurate as possible.
Be as specific as possible with voltage readings as this will help diagnose your problem quicker. If you do not know how to perform the above checks, just ask and I will try to guide you through it. Youtube also has some videos and as you know a picture is worth a thousand words.

Load test the battery at any auto parts store.

If you ground the coil kill wire you lose spark.

Well, the joke’s on me. My so-called “known good” batteries were anything but. One was putting out a whopping 2V and the other went to zero as soon as I hit it with a load tester.

One brand new battery and it fired right up. Just another lesson in the value of verifying your assumptions. One of those batteries was just bought in 2021 and the needle barely moved when I hooked it to the charger so I just ‘knew’ it was good.

Also when you buy a new battery, load test it before leaving the store.

That’s why I have included #4 in my procedure.

I’m just happy the problem was solved with a $28 battery and two bolts instead of spending 2-3 hours on my knees chasing wires and testing continuity.

I do find it interesting (and not in a good way) that my 2021 Ever Start (Walmart) battery didn’t even last two years. I took it in as a core to get a new battery at Rural King and when putting it on the battery core cart I noticed it contained several of the exact same battery. All were dated between April and September of 2021. It must have been a bad few months at the Colombian battery factory.

Elkins45 said:

I’m just happy the problem was solved with a $28 battery and two bolts instead of spending 2-3 hours on my knees chasing wires and testing continuity.

I do find it interesting (and not in a good way) that my 2021 Ever Start (Walmart) battery didn’t even last two years. I took it in as a core to get a new battery at Rural King and when putting it on the battery core cart I noticed it contained several of the exact same battery. All were dated between April and September of 2021. It must have been a bad few months at the Colombian battery factory.

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If you are buying underpowered CCA batteries and not occasionally trickle charging them, you will be lucky to get 1 to 2 years out of them. 275 CCA for single cylinder (minimum), and 300-340 CCA (minimum) for twin cylinder. A $28 dollar battery sounds like 180 or 230 CCA, not enough juice.

Tiger Small Engine said:

If you are buying underpowered CCA batteries and not occasionally trickle charging them, you will be lucky to get 1 to 2 years out of them. 275 CCA for single cylinder (minimum), and 300-340 CCA (minimum) for twin cylinder. A $28 dollar battery sounds like 180 or 230 CCA, not enough juice.

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This is the first mower battery I've ever bought that didn't last at least six years.

Elkins45 said:

I’m just happy the problem was solved with a $28 battery and two bolts instead of spending 2-3 hours on my knees chasing wires and testing continuity.

I do find it interesting (and not in a good way) that my 2021 Ever Start (Walmart) battery didn’t even last two years. I took it in as a core to get a new battery at Rural King and when putting it on the battery core cart I noticed it contained several of the exact same battery. All were dated between April and September of 2021. It must have been a bad few months at the Colombian battery factory.

Click to expand...

Why do you think they only have a 90 day warranty? They are lucky to make it thru that warranty at times.

Elkins45 said:

This is the first mower battery I've ever bought that didn't last at least six years.

Click to expand...

Well manufactures have gotten a lot better at making products that barely make it through the warranty periods as they cheapen the internals.

For the 50,000,000 time.
Every battery is thouroughly tested before it comes off the line
The ones that fail the tests get sent to Walmart, Lowes, Harbour Freight, etc
The best ones go to auto electricians
In many cases the same machine will make 20 different brands over 10 different capacities
The line is set up to make the top quality battery but only about 10% are perfect .

Now the fun bit
Wallys sell 1,000,000 batteries a year while the corner auto electricians might sell 100 .
So when they run out of junk batteries to sent to Wallys they put the junk brand stickers on better quality batteries to make up the numbers .