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Farmall 300 light switch?

A

Anonymous-0

Well-known Member
New to me is a Farmall 300 row crop,which appears to be in good condition. However,when I turn on the lights(has been converted to 12 V)a wisp of smoke is coming out the top. I need to remove the top cover plate and maybe dash to see if a wire is frayed but most likely an original light switch gone bad?. Is there repair or just replace? Appreciate your response, sometimes have hard time replying, but enjoy the forum!
 
(quoted from post at 09:48:29 07/29/11) New to me is a Farmall 300 row crop,which appears to be in good condition. However,when I turn on the lights(has been converted to 12 V)a wisp of smoke is coming out the top. I need to remove the top cover plate and maybe dash to see if a wire is frayed but most likely an original light switch gone bad?. Is there repair or just replace? Appreciate your response, sometimes have hard time replying, but enjoy the forum!
Click to expand...

Anytime there is smoke, there is heat, and the heat is caused by a less than ideal electrical connection. I'm not that familiar with the light switch on a 300, but you need to dig into it and have a look. The fix may be as simple as shining up the connections (clean, bright, and tight). The worst scenario is that you need to replace the entire switch. I think aftermarket replacements are available.
 
I would remove enough of the side hood to observe the light switch and wires in that area. If you have a short it will blow the fuse. If you have poor connections they will get hot and smoke. But, also, if the dimmer coil is wet or oily,( maybe someone washed tractor in that area) it will smoke until it dries itself off. This often happens when working on a tractor or a new tractor. The dimmer coil should only be energized in the dim position but it may be wired incorrectly. Personally, when I convert to 12 volts I eliminate the dimmer coil
 
Smoke means you're shorting out... but not necessarily within the switch.

It could be that one of your wires to a light is shorted, at the light, or anywhere along the pathway to the light.

Those old cloth covered wires don't age as well as the rest of the tractor.

The best way to fix that kind any wiring problem is slowly and methodically. it helps enourmously to have a multimeter to test with, but if not, you have to get creative.

Make a note of which wires go where, then remove them all. Test each one, one at a time.

If the switch turns out to be the culprit, it COULD possibly be serviced, but they usually only break down from corrosion, or something cracking apart. You'd save yourself a heck of a lot of trouble just buying a new one.

I believe they're in the $40 price range. Not cheap, but worth every penny compared to fighting with an old one.

But definitely check out all the wiring first. It will get twice as expensive if you throw in a new switch and it burns up too!
 
Oh Wait... I just remembered this circuit has a fuse! The fuse should blow if the circuit is shorted out.

Of course, that's IF the fuse is working properly. I'd try to figure out why it's not blowing. Sometimes people put bigger fuses in if they blow instead of solving the original problem. Or much worse, bridge them out of the circuit.

That's not the source of your trouble though, it's just letting your switch suffer from whatever the real trouble is.

Either way, if your switch is smoking, there's most likely too much current running through it for some reason.

You say it's been converted to 12v, I've never converted one to 12volts, so I'm not familiar with what must be changed during the conversion.

There is a resistor on the switch, going to 12v should make that get hotter than at 6v, but enough to smoke? I doubt it...

But, I guess not knowing what's normally done in a 12 volt conversion, I can't really help here!

All I can say is that if your lights ARE working through this smoke, I'd focus on that resistor. A short should be extreme, and disable the lights.
 
check for junk on the light switch resistor. chaff or hornet nests are common. Oil that leaked from the oil pressure gauge could also do that.

karl f
 
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