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John deere 6420 tractor problems
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JumpStartRider
Posted 8/1/2018 10:10 (#6905297)
Subject: John deere 6420 tractor problems


North Carolina		Please help me fix my 70 years old neighbors tractor. He has parkinsons and a bad hip. Im trying to make life as easy as i can for him.

First problem is a/c related. His air filters were clogged with dirt and mold. Evaporator clogged with dirt and mold as well. Condensor is clean and pressures looked fine before cleaning everything. But one of two fans under seat work. I changed the wiring connectors from one to other and now other one works. So are both fans suppose to be on at same time? I tried every configuration of fan blowing at every speed and adjustment and still only one fan comes on. He opened his doors when a/c stopped and tore off a door. Lol.

Second problem is pto. Pto went out and it turned on for 5 seconds then off again. I knew that was the sensor so i replaced and it works fine... Until neighbor called saying it doesnt work at all. Dash acknowledges that the pto switch is on, just no rpms and no pto spinning. Nothing. Not even an attempt. No codes either. Any other options besides pto clutches which is worst case scenario.



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JKM
Posted 8/1/2018 10:32 (#6905327 - in reply to #6905297)
Subject: RE: John deere 6420 tractor problems


Whitehouse		First up, when the fan switch is on, is there power at both fan connectors? Check with a test light or volt meter. From experience, there is a really good chance the fan motors are failing, especially after that much dirt making its way past the filters.

Second, doubtful the pto clutches have failed, with no load it should still spin some as the brake would be released. What kind of shape is the pto solenoid in? They are not unknown to fail. If you can, hook a pressure gauge up to the clutch and brake ports on the modulating valve ( rear, on the pto housing, top right corner of the housing, two ports, one labelled brake one labelled clutch.) should be in the vacinity of 200psi. I have seen dirt plug a hole in the back plate of the modulating valve.

If you get some pressure when the pto is switched on, the solenoid valve is at least working some. You can check for power at the solenoid valve, but you will need a second person, or a way to connect a volt meter to the connector, if the bcu doesn’t receive a pto speed reading within a few seconds, it will switch the pto relay off.
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JumpStartRider
Posted 8/1/2018 11:01 (#6905365 - in reply to #6905327)
Subject: RE: John deere 6420 tractor problems


North Carolina		Lots of info. Finally. Thank you. I assumed the solenoid would throw a code. Thats why i rulled that out. I will check some of this out on the pto.

One of the two fan plugs i assume does not have power. Both fans work, but not at same time, when i change the good harness between them. So i assume fan is not burned out. But i will check that as well with a volt meter.

Since you sound knowledgeable i will ask you one other thing. His electric gears went out last year. I pulled a code and it said k2/k3 solenoids circuit bad. I was going to check the solenoid for oil in the connector and ohm it to see if its good. What ohm should i be looking for? 11 ohm sounds right?

And should the pto solenoids ohm out at 10-12 ohms also. I hear i can change the pto solenoid out for the differential lock solenoid as well to see if that is what the issue is.

Thanks a million.
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JumpStartRider
Posted 8/1/2018 11:02 (#6905371 - in reply to #6905365)
Subject: RE: John deere 6420 tractor problems


North Carolina		Fyi... The fan that did not work initially was unplugged when i opened that plate. That had me puzzled. And not it came loose.... They were inches apart.
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brentnz
Posted 8/2/2018 04:57 (#6906643 - in reply to #6905365)
Subject: RE: John deere 6420 tractor problems


New Zealand		Pto solenoid should magnetise when switched on so should be easy to check by inserting a screw driver/ punch etc inside
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sonic
Posted 8/1/2018 11:32 (#6905416 - in reply to #6905297)
Subject: RE: John deere 6420 tractor problems


Maybe it should of went to the dealer. No good deed goes .
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DVFarms
Posted 8/1/2018 13:31 (#6905612 - in reply to #6905297)
Subject: RE: John deere 6420 tractor problems


Northern Kentucky		Cant help on the AC but I just had the same PTO problem and it ended up being the switch in the cab. I was puzzled as to why it acknowledges the PTO is on. Mine was at the dealer anyway so I had them fix it. But I swapped the solenoid and prox out and that didn't help.
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JumpStartRider
Posted 8/1/2018 14:35 (#6905688 - in reply to #6905612)
Subject: RE: John deere 6420 tractor problems


North Carolina		I had a spare new switch i tried. Didnt work.
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HoRFarms
Posted 8/1/2018 17:24 (#6905877 - in reply to #6905688)
Subject: RE: John deere 6420 tractor problems


SE VA/NE NC		If its the reversable two speed pto shaft, which rpm are you trying?

If 540, pull the snap ring off, pull shaft out and jb weld or rtv a quarter on the end of the shaft. The plunger on the tractor side of mine wore a small groove in the shaft, and the shaft would no longer depress the plunger fully. At first it would come on and cut off under load, then it just gave up completely. The quarter fixed it. A new snap ring cant hurt as they get worn and let the shaft work away from the plunger some too.
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JumpStartRider
Posted 8/1/2018 21:09 (#6906303 - in reply to #6905877)
Subject: RE: John deere 6420 tractor problems


North Carolina		I reversed it and tried 1000 and 540. I looked at the dimple to see if it was worn. Ill try to stick something on it an see if thats the issue. But it does not turn even when not connected to anything.
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JumpStartRider
Posted 8/2/2018 17:34 (#6907663 - in reply to #6905297)
Subject: RE: John deere 6420 tractor problems


North Carolina		The electrical plug has zero power on all fan speeds. Traced the wiring of non working plug and it runs to the rops and fuse panel... So so many wires i couldnt tell were it went. Confused as to why both dont combine at some point before the switch.

I checked pto solenoid plug. It has 8.6 volts. After plugging back in the in pto ran for 10 seconds. Then 5 seconds after i turned on again. And now nothing. It beeped when turning off and thru a code. Im checking that now.
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JKM
Posted 8/2/2018 19:52 (#6907863 - in reply to #6907663)
Subject: RE: John deere 6420 tractor problems


Whitehouse		Sorry for the delayed response. The mfwd and diff lock solenoid valves are the same. The pto solenoid valve is different unfortunately. With that said, if they are the older type with the square, removable magnet, the magnets are all the same and you would try swapping the diff lock and pto magnets in that case. The fact that it shut down and set a code after messing with the solenoid coil makes me lean heavily towards that coil being the issue. The controller does measure amp draw of the solenoid coil, too high( short) or two low (open), and it shuts off the circuit. Solenoid coil resistance should be 10-12ohms at 20 degrees C.

It is also possible the valve portion has failed in some way, but with the info you have provided I feel that is unlikely. The pto speed sensor could be defective however. In the 20 series, the controller does not monitor circuit continuity for the pto output speed sensor, it only monitors for a speed reading when the pto is switched on. If no speed is indicated within 20 seconds of switching the pto on the controller will switch off the pto. The pto speed sensor is just above or below the pto output shaft, and going by memory should show approximately 550ohms at 20C. Generally they show open circuit if failed.

As far as the fans, check fuses f5-13 and f5-14, both should be 20 amp. Each one supplies one fan with power. The fans share a common ground, through the resistor pack and switch. The positive wire goes directly from the fan to its respective fuse. Lead numbers are 222 and 231.

As far as the speed gears, it may have two, or three solenoids on the front right side of the transmission. Check them and their wiring for any damage, oil in the connector as you said. If there is oil in the connector, the solenoid valve has failed. Resistance should be 15ohms +/- 5 ohms at 20 degrees C.

Also, check the two 80amp fuses up by the battery for any signs of damage, make sure you pull the fuse out of the holder to check. They sometimes will melt or break a terminal off which you cannot see without removing the fuse.

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JumpStartRider
Posted 8/9/2018 13:17 (#6920285 - in reply to #6907863)
Subject: RE: John deere 6420 tractor problems


North Carolina		What do the two 80 amp fuses do at the battery?

Fans work. One fue was removed and the plug was unplugged under the seat. So it works and js blowing ice cold. The owner is very happy. Hopefully he can get some comfort.

The pto solenoid was badly corroded up top and reading 1.5 ohms. So i ordered a new one. Dirt fell into the solenoid hole, so i left solenoid out and started it. Oil came out of hole and hopefully cleared it. Solenoid should be in tomorrow.

Next is testing transmission solenoid. I will let you know what i find.

Also the seat does not work now. The 2 connectors for the seat show power. I figure something came uplugged under the cushion. Any idea. The seat height is all i know that isnt working now. It wjrked before but you really had to pull the lever hard. Ill look more into the switch for the seat height lever and get back to you.

And where do you get all of this info? A tech repair manual? I tried to look for one but could not find a new or used one. Let me now how you obtain your knowledge. Thanks a million.
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JKM
Posted 8/10/2018 04:52 (#6921309 - in reply to #6920285)
Subject: RE: John deere 6420 tractor problems


Whitehouse		The 80 amp fuses supply all the power to the tractor cab/fuse/controllers.

If the fans give up again check the relay associated with them, usually in the top left corner of the fuse panel, I have seen the terminals for them get loose over time and get hot enough to start melting relays as well.

As far as the seat height, does the compressor run? 99% of the time there is a wiring issue somewhere within the area of the seat suspension, wires pinched and broken, pulled apart, or broken off from fatigue. Probably the worst part of the tractor to work on is the wiring under the seat. One of the plugs you see is for the seat switch, the other supplies power for the compressor.
Most of my knowledge is from experience, 6 series tractors are my main workload, so get get pretty familiar with them. The most specific specifications come from a tech manual so I don’t get them wrong.

Technical manuals can be purchased here :

https://techpubs.deere.com/Products/ProductSearch.aspx


The most important one would be the diagnostic manual, the repair manual would be a close second.
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JumpStartRider
Posted 8/10/2018 08:07 (#6921599 - in reply to #6921309)
Subject: RE: John deere 6420 tractor problems


North Carolina		When pulling the seat height lever, ii do not hear the switch click to engage the compressor. So ill look to see if it pulled loose. I could of snagged the wire moving that seat. Its heavy..

I have the powerquad plus transmission with 2 solenoids on the side. The front one did not ohm anything. No oil in the plug though. Every other solenoid ohmed at 16.6 roughly. I checked every solenoid on the trannsmissio just to be sure.. So i ordered number #44. I assume all of the springs and other small parts will fall out when i change the solenoid and some hydraulic fluid will come out. Hopefully a 5 galllon bucket will catch it all. Or should i be prepared for more??

Both solenoids for pto and transmission arrive saturday. Ill let you know what i find.





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JKM
Posted 8/10/2018 15:29 (#6922440 - in reply to #6921599)
Subject: RE: John deere 6420 tractor problems


Whitehouse		When you remove that solenoid there won’t be very much oil that comes out, I usually have the new solenoid ready, spin the old one out, catch the spring and spool still in the bore with my finger, and screw the new solenoid right back in. Keep your head to the side if you don’t like the Taste of hyguard.

As far as the seat, get the skirt pulled down and start looking hard at wires. I had one once that would only work if you were sitting on the seat. Wire had a clean break inside the loom, no visible damage at all.
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JumpStartRider
Posted 8/16/2018 10:14 (#6932418 - in reply to #6922440)
Subject: RE: John deere 6420 tractor problems


North Carolina		A/c is ice cold. Pto works. Electric gears work. Thanks alot. The older farmer keep thanking me over and over again. I told him to really thank the unknown hero formally knowns as JKM.

Only issue was there was a little water sitting in botton of fans. On hot humid days a little bit of water comes/sprays from the vents on high fan mode. Not sure if condensation in vents from being so cold, or if its blowing condensation from fan/evaporator area... I sucked water out from fan when i was in there cleaning and tried to look for a drain to clean it, but could not find it. The drain works, as i can see water draining from it, just probably not fast enough. And i only see it from one drain. I figure there are 2, one for each side.
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JKM
Posted 8/16/2018 17:31 (#6933044 - in reply to #6932418)
Subject: RE: John deere 6420 tractor problems


Whitehouse		Well that’s the first time I have been called a hero. Just trying to be helpful. I am glad everything is patched up, should be easier on your neighbour having everything working right.

You are right there are two drains, one for each side, and I can not remember but they are either right under the evap core, or right under the fans themselves.


The artist formally known as JKM.
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