JD 4105 electrical problem

[Ross33]

My John Deere 4105 has been having an intermittent electrical problem for years - although it appears to be permanent today.

The tractor starts fine and runs well but the engine dies immediately when it is shifted into gear or the PTO is engaged. Usually, I can get past the problem by dropping the FEL repeatedly to shake the tractor and other kludges but so far today, none of that works. I think that it is a loose connection in the wiring harness but the JD dealer repair did not help any. Ross

 

[CADplans]

That sounds like a seat switch problem??

 

[beenthere]

Ross
Welcome to TBN

Give us some more feedback from your experience.. may be able to help track it down.

Try putting in jumpers to keep safety switches such as the seat switch closed and see if the tractor still acts the same.

 

[Ross33]

Ross
Welcome to TBN

Give us some more feedback from your experience.. may be able to help track it down.

Try putting in jumpers to keep safety switches such as the seat switch closed and see if the tractor still acts the same.

Thank you for your speedy response. Yesterday morning, I was able to put the tractor into gear and then I used the brush beater and FEL for an hour or so. But then the engine died and again, it will start but it dies if the gear shift or PTO are engaged. Now the tractor sits forlornly in my north pasture.

My tractor seat switch was removed several years ago and the wiring connector now has a jumper to bypass that switch (close the circuit). What other safety switches can possibly be bypassed by a jumper?

There is a two pin connector that plugs into transmission housing below the left rear axle. This connector is often jerked out brush and when that happens the tractor will not start at all. This connector does not seem to be a problem currently since, if it is unplugged, the motor dies immediately (rather than the engine dies only when engaging the gear shift or the PTO).

I have used contact cleaner on most of the accessable connectors in the wiring harness but that has not changed to current problem.
Ross

 

[MTGreen]

I would look closer at that seat switch connector and your bypass to see if anything has changed or corroded. Since it's happening instantly with both gear and PTO engagement it's likely the operator presence (seat) switch portion of the circuit. I had a Deere seat connector that had a spring loaded mechanism inside the connector itself that would make/break the connection internally which was designed to prevent folks from bypassing it. I don't recall now exactly how it worked but it had broken internally and gave me fits trying to figure out what the problem was. I tore out the broken spring loaded mechanism inside the connector and was back in business

 

[LD1]

Yup, seat switch.

Surprised it was just a two wire switch. Because most of them are 3 wire because its a 3 position switch

 

[Ross33]

This morning I replaced the jumper wire to the seat switch connector (attached image) and the tractor worked properly - for 10 minutes or so. Then the engine died and it was back to the same problem. So I trimmed the insulation for the wires feeding the seat switch connector and I twisted them together (another attached image). There was no improvement - the tractor starts but cannot engage gear or the PTO.

 

[MTGreen]

Since it ran properly for 10 minutes it seems we may be in the right track. I suggest looking at the business end of that connector and seeing if there's a spring and bar in there

 

[Ross33]

I checked all of the fuses and replaced 2 of the 10A mini fuses. My tractor is working properly now. Hopefully the electrical fault will not re-occur anytime soon.

Thanks everyone for the information and the support.

Ross

When my dad taught me how to drive his tractor 60 years ago, there was no seat switch - or any other safety devices that could cause problems. But then he was responsible for most of the tractor maintenance.

 

[Ross33]

The fuse replacements yesterday were apparently irrelevant. This morning my intermittent wiring problem was back.

I noticed that a part of the wiring harness had a wear spot so I squeezed the wires there. This re-enabled my ability to engage the gearshift/PTO functions so now I am good to go again. I will examine the worn part of the wiring harness later today.