# Husqvarna Zero Turn RZ5424 Mower Won't Crank



## talkin (Apr 9, 2011)

Colleagues,

I have a Husquvarna RZ5424 Zero Turn Mower that won't crank. A 24 hp Kohler engine is onboard. The battery is fully charged, brake is in the locked and upright position, driver is in seat to keep the cutoff switch happy and the control arms are in the correct position for start. 

The technique to start is to turn the key quickly from fully off to on. The response is no sound. I suspect a starter module or defective key module. But the manual for the unit doesn't get into this level of detail for assistance.

Will appreciate any advice or suggestions. Thanks, tom


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## pogobill (Jan 31, 2012)

Check the ground connection and the connections at the battery.


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## Bob Driver (Nov 1, 2017)

3-prong, or 4-prong starter solenoid??

*3-prong*









*4-prong*









Or is the Solenoid built into the starter?


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## talkin (Apr 9, 2011)

pogobill said:


> Check the ground connection and the connections at the battery.


Colleague, thanks for the tip. I thought about a loose ground issue and will check it out.. The battery connections are firm. Thanks again, tom


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## talkin (Apr 9, 2011)

Bob Driver said:


> 3-prong, or 4-prong starter solenoid??
> 
> Bob, I don't know the answer. I need to look at it to check it out. Thanks for the tip. Tom
> 
> ...


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## Bob Driver (Nov 1, 2017)

Makes a big difference in the trouble-shooting process once you go beyond checking your wiring connections


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## talkin (Apr 9, 2011)

Bob, it's a 3-prong. I ordered a new one just to have it. I checked out the ignition switch and got some continuity failure so I replaced that too. Problem is it still won't crank. I realize I have to check the starter now and seat cut off, etc., --- what a pain.


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## talkin (Apr 9, 2011)

Well, I replaced the solonoid and the ignition switch. Continuity tests for both failed. But the mower still won't start. The battery has discharged 1 volt. It's on a charger. Now I am getting clicking under the right control arm. I assume that's a safety switch under there.


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## Bob Driver (Nov 1, 2017)

If it's a 3-prong switch that makes the wiring much simpler. Everything is in "series"...... 
1) Starting at the S terminal on the key switch. 
2) Runs through the brake switch (has to be closed)
3) Runs through the PTO Switch (has to be closed)
4) Runs through the Arm switches (has to be closed)

Normally a safety switch doesn't "click", it's more than likely a relay.


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## talkin (Apr 9, 2011)

Bob, thanks. This helps. I'm stumped at the minute. It's probably something simple I haven't discovered. The battery is fully charged. Now, when I turn the key, I get a clicking sound. Sometimes, it sounds like it is under the PTO panel. Sometimes, it sounds like it's somewhere under the seat. Once, I could hear the new Solonoid clicking. I've checked the ground wire to the engine --- it's intact. I'll check out where all the relays are. Thanks.


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## Bob Driver (Nov 1, 2017)

Wiring diagram shows it's pretty straight forward.....

1) YELLOW wire coming off S terminal at key to PTO Switch
2) YELLOW from PTO switch to left arm lever
3) YELLOW from left arm lever to right arm lever
4) YELLOW from right arm lever to Brake switch
5) YELLOW from brake lever to starter solenoid
6) 3-prong solenoid grounds to the frame through the mounting legs

All switches have to be *completely closed* for start signal to reach solenoid. Start tracing the yellow wire from the key switch. Hit the key(to start)-- You should see battery voltage going into each switch. Then check for battery voltage coming out of each switch. Battery voltage into the switch, but not out..... Bad switch, bad contact, or the switch is not closing fully. 

https://www.manualslib.com/manual/502617/Husqvarna-Rz5424.html?page=49#manual


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## talkin (Apr 9, 2011)

Tractor

Bob, thanks for your help. Electrical testing is not a core skill set for me, as simple as it may seem. I would have taken this mower to a shop for help long ago but many service companies in my area are closed because of COVID or backed up for 4-6 weeks.

I ran continuity checks on all wires. No problems.

There's two yellow wires running throughout the mower starting at the ignition switch. I thought from your comments these might be inbound-outbound yellows throughout. But the diagram shows only one yellow running from the S terminal on the ignition -> PTO -> left arm -> right arm and terminating at the brake switch. 

I've been able to test yellow in each of the following with no findings:
1. Within the ignition 
2. Within the PTO 
3. From the PTO to a yellow in the left control arm.
4. Within the left control arm

Can’t get at the right control arm wires. The continuity check I’ve been able to do with the probe reveals no problem.

I don’t believe in throwing parts at a problem. But I’m thinking it might be easier to replace the wiring harness. They cost $65. I can’t tell from the wiring diagram if the switches and relays are part of the wiring harness. If I knew they were I’d just order it.

Thanks. tom


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## Bob Driver (Nov 1, 2017)

Flip the dial on the VOM over to voltage and then confirm your getting battery voltage, at the small stud (yellow wire) on the starter solenoid.


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## talkin (Apr 9, 2011)

I read on another site the fuel solenoid causes this problem (clicking when the key is in the run but not start position).

The battery is at 12.6 volts when not under load. Is it normal for it to be at 8.5V after I turn it to start?


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## Bob Driver (Nov 1, 2017)

You usually can hear/feel the fuel solenoid click when the key is turned to run. The fuel solenoid has nothing to do with the start circuit engaging.

A near 25% drop in voltage on any circuit is way to much. Where are you measuring that massive drop? If it's at the main stud on the starter, disconnect the lead and then measure it. If it's back to 12.6V, you've got a bad starter.

Here's a PDF that shows how to do a quick voltage drop test on both the positive and negative side of a starter circuit

https://drivcat.com/docs/1519.pdf


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## talkin (Apr 9, 2011)

Bob,
I thought I'd get back to you for some closure on this given all of your thoughtful help. I found the problem and, surprise, surprise, the problem was me -- so-to-speak.

It turns out the battery was bad. When I tested it offline it was 12.5 volts. When I turned the key on the ignition, it dropped to 8.5 volts. I should have read this red flag correctly. Instead, I assumed the dropoff in voltage stemmed from the ground or some other issue since I had found continuity problems in the ignition switch and the solenoid. I figured there was probably another problem down the line too. 

This is another great example of assumption is the mother of all ....up's. Occam's Razor applies here. The simplest explanation is usually the right one --- and I missed it by a mile. Glad I wasn't in a competition to fix this thing --- I would have come in last! Thanks again, tom


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## Bob Driver (Nov 1, 2017)

One of the tools I use the most in the shop is a battery load tester. I wear that thing out in the Spring... Customer machines have sat all winter, so I routinely load test every battery, on every machine that comes through the door.

Buying a load tester is kind of tricky. You're supposed to load test a battery to 1/2 of it's amperage capability for 10 seconds. For a 300 amp lawn mower battery, that's 150A. Here's the $20 HF load tester I use, but it's only a 100A load, so I go 15 seconds on the test.

https://www.harborfreight.com/100a-612v-battery-load-tester-61747.html

That thing is pretty much worthless on a car battery. For that, you need to step up to a 500A carbon pile tester, which is overkill in the way of a battery tool for most DIY guys.

https://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html

Don't feel bad about your mistake, it happens to me all the time. I spent 5 minutes the other day with a VOM (and that damn load tester), testing/cussing a zero turn that wouldn't crank and the only thing I did was change the oil and grease it.... You know that parking brake lever has to be set to crank.

The good part about your whole ordeal is that you are now officially more familiar with the start circuit wiring on a Husqvarna RZ5424 Zero Turn Mower than just about anybody within a several mile radius of you.

It always feels nice to be a community leader at something.... I'm currently ranked #1 for setting the parking brake before you crank for all of Endville, MS (population 43).


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