I have a Scag STT52A-23KA that will only start if I jump a wire to the left drive arm safely switch wiring. The switch itself is fine but there's no voltage coming to the switch. If I jump a wire to the harness; I can hear a slight click when I turn on the ignition and the mower will start. I replaced the safety module and it still has the same problem. Is there something else I should be looking for. Engine is 23hp FD671D-AS01.
Scag safety switch.
DOUGE2
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I have a Scag STT52A-23KA that will only start if I jump a wire to the left drive arm safely switch wiring. The switch itself is fine but there's no voltage coming to the switch. If I jump a wire to the harness; I can hear a slight click when I turn on the ignition and the mower will start. I replaced the safety module and it still has the same problem. Is there something else I should be looking for. Engine is 23hp FD671D-AS01.
A broken wire or bad terminal connection.
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90% of all electrical issues are due to poor terminations...meaning where the wire connects to a relay etc. I have encountered numerous issues with a connector that was never properly seated, yet may have been in use for years until it finally becomes an issue. A few weeks ago a guy I know called and asked about his new (2 month old Deere) not starting, nor even turning over and wanted me to diagnose and repair his problem over the phone, sure, I'm psychic! LOL The first thing I told him to check was all of the terminations, or connectors, there's really not that many... he called back 5 minutes later and said there was a connector that was evidently never fully seated from the factory as it locked into place, and it fired right up.
As J. Baker nails it, after the connections are found good then things become a bit more "fun". Chasing down a bad wire or harness can test one's patience to be sure! But is a lot cheaper than paying a dealership $85 hr to diagnose and R&R. A good Fluke multi-meter should be in every toolbox, it can save you a lot of money!
As J. Baker nails it, after the connections are found good then things become a bit more "fun". Chasing down a bad wire or harness can test one's patience to be sure! But is a lot cheaper than paying a dealership $85 hr to diagnose and R&R. A good Fluke multi-meter should be in every toolbox, it can save you a lot of money!
I've searched all over it for a bad connector or damaged wire and they all appear to be visually fine. All the other switches have voltage except that left handle. I will recheck all the connections again though. Thanks for the advice. If I run a wire from the battery to the harness on that side; the mower starts and runs.
Thanks J Baker. I'm going to recheck harness again. Perhaps I may have missed something.
Then you are looking for issues with the wire that feeds that switch. Focus on only those connections, not every connection.
A simple test light fixes almost everything on a lawn mower. You don't need a meter until you are testing low voltage signal wires on engine sensors. For basic start/run and safety circuits, a test light if sufficient. Sometimes I make my own test light when I need to place a load on a circuit. Modern test lights sometimes use LED lights. LED lights will illuminate with low voltage or sometimes even faulty connections. Meters do the same. Sometimes you need to place a load on the circuit. A headlight wired up as a test light makes a good test tool. Done it many times. The light is large enough to create a load, and shows a bad connection fast.
A power probe is also a great tool for simple 12V circuits. Meters are great and have their place, but aren't much use in high load 12V circuits. Too easy for a single wire to carry 12V and the meter read just fine, but once a load is placed on the circuit, it fails. If you do use a meter, test without the load on, and with the load applied and look for a voltage drop.
I've been using a test light and I do have a basic meter ( nothing fancy). I'm going to focus on that circuit as you suggest . Thanks
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I just wet the tips of my fingers and put a lightbulb in my mouth...
![Image]()
That seems to only work with AC voltage
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So you have an open wire to that safety switch. You have found that out by using a new wire (jumper) to supply 12 volts to that circuit to make it work. Why go any further in trouble shooting the wire to find the exact break in the wiring harness. The fix is to replace the broken wire and you have already done this by installing a jumper wire.
Because for all we know it is a bad connection at a terminal. Or the wire broke at a terminal. Could be an easy fix. No need to be lazy and go adding wires yet.
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