John Deere 5425 won’t start as if the battery were dead but the lights work quite well

[Brown Dog]

As mentioned : it’s probably the ignition key switch.

 

[k0ua]

Lots of things to "look at" All time wasters when a simple voltmeter placed on the battery terminals will tell you what you need to know. You will need a 'helper" to try the starter while you monitor the battery voltage. If the battery voltage RIGHT ON THE BATTERY terminals themselves does not fall precipitously than the problem IS NOT all the connection, corrosion, ground terminals etc. The problem is further down the line. Keyswitch, starter relay, starter solenoid and most likely, a safety switch. BUT if the battery voltage falls like a rock, the problem is one or all of the connection problems as outlined by others. Why guess at these things when it only takes a few seconds to test and form a hypothesis of the actual problem? Get a voltmeter, and understand how to use it. One actual test that takes about 10 seconds will tell you more than all the poking, prodding, pulling and guessing in the world.

 

[k0ua]

Heck for that matter, you don't even absolutely have to have a voltmeter if you are good at estimating voltage drop by observing the lights. Turn on the lights, turn the key to start, do the lights dim a bunch? If not, it aint a connection problem. Did you hear the start relay pickup? Is it quiet enough to hear it click? If the starter relay don't click then it will never pull in the starter solenoid now will it? There can be dozens of reason's why the starter relay does not pull in. From defective key switch to many safety switches to rat chewed wiring and on and on. How are you going to troubleshoot these problems without your voltmeter and the knowledge to use it?

 

[jaydee325]

Electrical trouble shooting 101: Start with a fully charged battery that has been verified good by a load test. Most every big box auto parts store will load test a battery for free.

I have used K0ua method too, but unless you know what you are doing with a volt meter and know what you are looking for, go the load test route.

Without knowing you have a good battery, you are just wasting time.