Farmall 300 wiring diagram

[300guy]

Does anyone have a wiring diagram for a Farmall 300? The instrument light (above the dash) with the small bulb has decided to come on and stay on. So I just took it out so it would not run the battery down. But I do not know why it is staying on all the time?????

 

[used red MN]

Do you have working lights on the tractor that are operated by the original rotary switch? If not, then you simply bumped the light switch to the on position. Here is a past YT thread with a wiring diagram for a 450. Past YT thread with diagram The x50 series wiring should be the same as the x00 series except the x00 series utilized a combination ignition switch/start switch, where the x50 used a on/of key switch and a separate start button as shown in the diagram.
If the accidental switch on is not your problem I would say that you have wires or terminal ends touching behind the switch causing your problem. Make sure when you pull the dash panel out that you have the battery disconnected. If you need to reconnect it to test with the panel open make sure the switch terminals are away from any thing that could short them. A piece of cardboard bent and laid across the bottom edge of the opening in the dash/kick panel is not a bad idea. Also depending on how much slack there is in the capillary tube lead for the temperature gauge that could determine how far the dash will pull out just a warning to be aware and not damage that. Of course the wires will limit the slack as that as well.

 

[300guy]

I don't have the stuff listed in the diagram for the 450. So it is not really close to what I need.

 

[used red MN]

I don't have the stuff listed in the diagram for the 450. So it is not really close to what I need.

Okay, I forgot it was showing an alternator. That really isn’t involved with your light problem and stuff under the dash, that will be as shown in the diagram. What’s your intention, you want to do some rewiring or just fix the problem? Pull the dash out or at least take it loose and tip it out a bit so you can see the connections, if there is a problem behind there such as on the switch connections you will likely find it. Some sites say the operators manuals they offer include the wiring diagrams I don’t see YT mentioning that. Farmall 300 operators manual from YT
Edit to add: Again if you are messing with the dash make sure you disconnect the battery cable. On those tractors, as it was for many IH tractors through the 60s, there is no fuse to the power to the ammeter. If it shorts to something it usually results in burnt wiring.

 

[D Slater]

Does anyone have a wiring diagram for a Farmall 300? The instrument light (above the dash) with the small bulb has decided to come on and stay on. So I just took it out so it would not run the battery down. But I do not know why it is staying on all the time?????

Goes down to terminal on light switch. If everything original, it's on the wrong terminal or something wrong with switch or whatever. Not sure but think it went to terminal closest to bottom with switch mounted normal way.

 

[300guy]

No that wire did not go to the switch. I would really like a diagram so I could see how all the sights are hooked to the switch and such.

 

[used red MN]

I would really like a diagram so I could see how all the sights are hooked to the switch and such.

That 450 diagram in the linked thread above shows you for cripes sake. Connect it to a terminal that operates the tail light and go on with life.
Or buy a manual.
Or call dealer Carter & Gruenwald in WI here’s a link. C & G in WI
I had online wiring diagrams for almost all IH tractors through their website. They made some website updates and all the links got broken. Someone came on a thread here recently and said he was involved with setting up new links. I failed to save that communication so I don’t know the status of that project.

 

[used red MN]

No that wire did not go to the switch.

So then tell us where it does go? It had to go to some circuit that is controlled by the light switch. Have you had this tractor since it was new? If not how do you know the wiring has not been modified?

 

[300guy]

The wire goes into the loom where the light wires come out of the light switch. There are three wires on the switch, a starter wire, an ignition wire and a battery wire. That's it. Please just find me a diagram.

 

[Jim.ME]

The wire goes into the loom where the light wires come out of the light switch. There are three wires on the switch, a starter wire, an ignition wire and a battery wire. That's it. Please just find me a diagram.

I am confused, your description of the switch sounds like the ignition switch, not a light switch. Does your tractor have a separate, dedicated light switch?

 

[Jim.ME]

From the parts book it appears the wire from that dash light goes to a terminal on the light switch, just the same as the wiring diagram for the linked 450 shows.

If your wiring is original, it should be easy to trace wire 45 from the light back down to the light switch and see if the light switch has gone bad, and that terminal is staying hot.

 

[300guy]

Thank you!

 

[300guy]

From the looks of that maybe the wire going to that light got bent so it is touching a terminal on the light switch. I was in the dash a week ago trying to put a new switch in because I and another guy though the switch was not working correctly as it has started or tried to start when the key was released. I bought on from O'Reilly and modified it by drilling holes for bolts to hold the wires on the terminals. When I put it in that same day, all the lights came on and the key would not snap back to the run position. So I took it back out and put the old one back in. Started it up and took it out to push some dirt. After about 230 minutes of running the tractor just stopped. Test light showed me power going in and nothing out of the brand new oil I put in last Nov. Took the old coil and put it in and the tractor started and ran fine for the next hour!!! Coil is going back to this parts site.

 

[Jim.ME]

I asked if your tractor had a separate dedicated light switch, as you were referencing the ignition switch. The dash light is supposed to be wired to the light switch, not the ignition switch by the drawings. What I get here is that you were working on the ignition switch, as you mentioned battery, run and start positions earlier, and in the process, you may have caused a problem with this wire making it contacting another wire (likely the battery power wire/terminal) on the light switch, is that correct?

If the ignition switch won't spring back to run after you were drilling holes for screws in the tabs, I have to guess you damaged it.

If the points were closed when you tested for power through the coil with a test light, it would not be uncommon for the light not to show power on the coil's distributor side terminal as the path through the points should be less resistance than the test light bulb's resistance. The points opening and closing is what makes the light flash on and off when doing a test of the points on a cranking engine, with a test light on the coil's distributor side terminal.

 

[used red MN]

Took the old coil and put it in and the tractor started and ran fine for the next hour!!!

You imply the coil fixed it and made it run. Your coil test “of power out of the coil” would only be valid if the points were open or if the lead from the distributor was disconnected.
Sounds like a simple short due to two circuits coming into contact was the issue with your dash lamp. There is not a lot of room behind that panel. That may have been one of the reasons IH went to the separate on/off key switch placed lower in the kick panel on the x50 series. Telling the entire story of what took place would have been helpful. Someone probably has a wiring diagram for it, but apparently they didn’t view this thread. Hope it treats you well.
I see Jim.ME has replied and is saying some of the same things I already typed.

 

[300guy]

First I’m not a beginner. Taught auto for 35 years and worked in an IH shop for10 years before and during college.
Yes the wire was off the distributor when I tested the coil. It won’t even fire when I tapped that wire to ground.

 

[used red MN]

First I’m not a beginner. Taught auto for 35 years and worked in an IH shop for10 years before and during college.
Yes the wire was off the distributor when I tested the coil. It won’t even fire when I tapped that wire to ground.

Sorry if you thought I was implying anything. I like helping people out but I am not dedicated to the point where I keep a “skill level record book” on members. The majority that come asking for help here usually have a reason for it, you are an exception.