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a simple vom will do it once you have it out, any resistance more than a few ohms between the posts (really should be 0 ohms) when the switch is placed in the used positions and if it is kinda where you have to wiggle it to read the reading ,replace it. these factory switches do go out, so a better quality replacement is not a bad idea.
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If you have a schematic and either a multi-meter or a battery and a test light it should be easy enough to test the switch either in the machine or on the bench.
It is also possible without a schematic but is a little more work.
Without knowing your electrical skill level it is hard to know how basic of a description you need.
First advice is to take a picture of the wires before you disconnect them. IF that is not possible, be sure and label them well so you can get them back where they belong.
A lot of people have upgraded to a Ford key switch which has better contacts and can take the load of the glow plugs better than the factory switch.
All of the wiring on these machines is barely adequate to function properly when new. As they age most of the spade connectors corrode and become loose. Both the crimp on the wire and the crimp that holds the female end onto the spade. This causes intermittent connectivity that manifests itself as all kinds of different issues.
If you follow the power from the battery to the switch it probably goes from the battery to a terminal on the starter, then to the amp meter then to the switch. Then the switch contacts will in turn energize the run, start and glow plug circuits. Fortunately these are done only one at a time so checking for continuity is straight forward.
You probably have a switch with the following positions from left to right.
Start – Off – Run – Start – Heat (glow plugs)
The start and heat positions are spring loaded and will not stay in those positions unless you hold it.
The run sends power out to the fuse box to power all the other accessories.
Either start will send power to the starter solenoid, probably through the same wire spliced together close to the switch.
Heat will go to the glow plug bus bar through the fuse in the fuse box.
What symptom(s) are you having that cause you to suspect the key switch is the issue?
Hope this helps and ask any questions you still have. Post pictures if you can.
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Take a look at the files on my web page here:
http://www.harnerfarm.net/Jinma/Jinma284.html
The wiring for you dozer should be similar to the 284 tractor wiring. Also the file for the Ford switch shows the pin out of the switches.
Feel free to download and print out the files. I didn’t make them but posted for anyone who needs them.
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Wow, lot of good information. I researched YouTube and found how to bench test the switch. As I suspected, the switch is bad. I have since then ordered a replacement switch from an online dealer. The original switch became suspect when I went to start my dozer one day and nothing happened as I turned the key to start. I thought the battery was dead so I put the battery on charge even though my meter said it had a good charge. After being on the charger overnight I tried again and the same thing happened; no start, no lights, no nothing. I was able to get the dozer started by placing a remote starting cable onto the starter. The dozer fired right up, no problem. However, this is not an ideal situation since I am bypassing the glow plug. I hope to have the dozer back in operation in order to complete spring and summer chores. Thanks again for all your help and advice.
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Okay, so the saga continues;
I installed the replacement ignition switch with no problems. However, now everything works, the light switches, the amp meter, the tach, etc. Everything but the starter, when I turn the key to the start engine position, nothing happens. This is the whole reason for suspecting the ignition switch in the first place. If I jump the starter at the starter the tractor starts up. What could be the problem?
I have attached the wiring schematic taken from the manual, perhaps someone with more experience can diagnose the problem and offer suggestions where I can look for potential problems.
I have marked the schematic with two question marks, what are these switches? if the switches malfunction could this be a problem?Thanks in advance for your help
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just as a fyi the start circuit is the hardest thing the switch does, It will extend the life of the switch by adding a start relay to the starter solenoid so the switch carrys only the load for the relay and not the starter. And the same can be done for the glow plugs. I also believe that the start switch restricts the amount of amps the starter wants making it not engauge as it should getting the engine to the proper starting rpm , moreso when cold temps are there. Just a thought.
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Hi David,
Thanks for the info. I was wondering if you had a wiring diagram to hook up the relay I received. I want to make sure I am hooking it up right. The lettering on the replacement starter relay is written in Chinese. I used a translator app and I have attached a copy of that to this reply.
Sorry I am such a doofus when it comes to electronics.
Katfish
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no I do not but, I think I can write it so you can understand. I will need to know something though . How many posts are on your relay 3 or 4?
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I think I figured it out. After watching several YouTube videos.
The problem seem to be that I needed to have a separate 12 volt connection to the post labeled “power supply”. Without that the solenoid would not transfer power to the post labeled starter.
The post labeled “Ignition switch” is where I landed the input from the ignition switch, post #4.
It seems to work now, I can now start the tractor from the ignition switch.
The relay has 4 posts, see the attachment I included.
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