4020

Olddeere · Jan 18, 2017

Hi everyone love this website lots of help
with my older tractors on how to get them
back up and running. Having a problem with
my early model 4020 though cant get my
lights to work i have read that there is
circuit breakers or fuses on the wiring
harness under the cowel but i can not find
them for the life of me. The generator and
oild lights work and gauges on the dash work
its just no lights. Any help would be
greatly appreciated.

David G · Jan 18, 2017

There are two circuit breakers mounted on the back of the access panel under the steering wheel.

Tx Jim · Jan 19, 2017

Parts key 45 are the circuit breakers David G referred to their location. One needs to remove capscrew(key 48) to remove cover(key 46) to access circuit breakers.

Also if electrical system is still 24 volts be sure wire or inline fuse is attached from rear LH battery(+) post to tractor frame. This wire or fuse I mentioned gives a way to split 24 volts to 12 volts to operate lights & fuel gauge

Tx Jim · Jan 19, 2017

8) in previous post was supposed to an 8 as in 48

David G · Jan 19, 2017

We mentioned the location of the breakers, but not the trouble shooting. There are two "separate" electrical systems, about half the lights are on one breaker and the other half on the other. Please tell us what lights do not work and we can help from there.

tim s · Jan 19, 2017

If you are still using 24 volt system there is a small ground wire from the right battery to the frame that could have a fuse in it, or broken off,,With the 24 volt system you can chase your tail for hours and not find the problem...

David G · Jan 19, 2017

I still cannot figure out why Deere did a system like this, a series parallel switch would have worked fine.

Olddeere · Jan 19, 2017

Still has the 24 volt system in it i have all the items to convert over to a 12 volt system came with when i bought the tractor but kinda want to keep it with the original system in it if i could. no lights work at all just the dash works not the light on the dash just the gauges.

Tx Jim · Jan 19, 2017

(quoted from post at 15:38:59 01/19/17) Still has the 24 volt system in it i have all the items to convert over to a 12 volt system came with when i bought the tractor but kinda want to keep it with the original system in it if i could. no lights work at all just the dash works not the light on the dash just the gauges.

I understand your desire to keep your 4020 original but you'd have a lot less headaches if you'd convert it to 12 volts.

erskine2017 · Jan 19, 2017

Deere used the 24 Volt system for 11 years on diesel tractors. It is a misconception to think of the system as "split". The lights are in series with each light consuming 12 volts. When the system is working properly with balanced loads there is very little current in the middle wire. If the loads are balanced the lights will work with the middle wire unhooked. The middle wire is there so you will still have a light if a bulb in series burns out. Without a middle wire the fuel gauge would not work with the lights off, but would with the lights on. With the tractor running the generator (not the batteries} is the source of voltage and current. The lights would work with the batteries out of the circuit. With the generator running it is easier to visualize that the light circuit is not split.

tomstractorsandtoys · Jan 19, 2017

I farm with about eight 3020-4020 Deere tractors that were 24volt. Do yourself a favor and change it to 12 volt especially if you already have the parts. There will always be something wrong with the 24 volt system.When changing over I usually make my own new harness as the old ones are usually full of cracks and splices and they also contain some wires that are not needed. Tom

David G · Jan 19, 2017

You stated that the dash lights work, that means that half the lights would work if breaker issue.

I think you might have a wiring harness issue.

rick deere · Jan 19, 2017

If your tractor is 24 volts , never turn lights on if tractor is not running will blow lights.Start by seeing if you have current to lights.

David G · Jan 19, 2017

Where did you come up with that idea?

I have done it 100s of times, there is absolutely no reason for that.

Tx Jim · Jan 20, 2017

(quoted from post at 22:01:15 01/19/17) If your tractor is 24 volts , never turn lights on if tractor is not running will blow lights.Start by seeing if you have current to lights.

I agree with David as back when I was a JD dealer service manager I've turned on or witnessed lights being turned on a 24 volt system without engine running many times with no sealed beam failures.

Turning lights on with little ground wire or inline fuse absent on rear LH battery post to frame can cause STRANGE things to happen.

Olddeere · Jan 20, 2017

Didnt get to work on the tractor yesterday
but there is no power at the lights took my
multimeter to check. I have moved batteries
around before and i dont ever remember a
little wire that runs off the batteries. All
there is is the connecting cable, the one
that goes to the frame under the cab and the
two that go up to the starter all the same
size. And sorry if i miss lead u there are
no lights that work anywhere even on the
dash just the gauges. which reading the
electrical diagram lead me to believe it was
the circuit breakers.

tim s · Jan 20, 2017

There were a couple different wiring diagrams, some did not use the little wire with the fuse,, a bad connection in the big plug that is under the hood can cause a lot of confusion..you can drive your self the rest of the way Crazy with a 24 volt system,,,switch it over to 12 volt before you become Suicidal...

David G · Jan 20, 2017

I would fix this issue before attempting any change to 12V.

Do make sure there is a white wire with good fuse between the common connection on the batteries and the chassis, if not correct.

Take the panel off and lay it on the floor boards.

I am thinking the breakers are first in line for power and always hot, please correct if not.

Take multimeter set on volts, measure from ground to each side of breaker, both should be hot.
If only one side of breaker hot then problem is breaker.
If neither side of breaker hot, then problem is in the wire that runs to the starter, with big loop on lug, there should be a brown wire and a blue wire.
If both sides of breakers hot then good to here.
Then to ignition switch
Then to light switch
Then to wiring harness

Maybe someone could list out what devices are on each side to the power, that helps to isolate, you did say the oil light works, how about horn, starter and plug on back of tractor.

Tx Jim · Jan 20, 2017

DITTO what Tim stated on changing to 12 volt system!! Factory ground wire for 24 volt system for headlamps/accessories is ""key 30""!!!!

David G · Jan 20, 2017

I was incorrect on fuse and white wire.

Does the go back to plug?

Tx Jim · Jan 20, 2017

Inline fuse holder with a slow burn fuse(AR47713) in lieu of wire was offered with a wiring harness replacement package that also included 2 circuit breakers that mounted on a plate at starter.

rick deere · Jan 20, 2017

than keep on doing it.

Olddeere · Jan 22, 2017

Okay I think I got it figured out it's the
light switch on tractor but I only have one
power lead going into it shouldn't there be
two. So I jumped the power over to get the
lights on but they're only reading 9.3 volts
is that right. And the negative that is
grounded to the Tractor frame has no fuse in
it is that a big deal.

Tx Jim · Jan 22, 2017

Lights & fuel gauge are powered by two 12 volt circuits identified as Bat A & Bat B. Each circuit should have 12 volts. Fuse for ground was field added to some 24 volt models after tractors rolled off assembly but fuse wasn't required just better way to help eliminate electrical fires in conjunction with field installed circuit breakers.

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