John Deere 6420 problems and how to fix them.

Are you a John Deere 6420 owner? If so, you’re likely well aware of the impressive performance and reliability of this machine.

However, as with any piece of heavy equipment, the 6420 is not immune to problems and malfunctions. Whether you use your tractor for farming, landscaping, or other applications, encountering issues with your equipment can be frustrating and costly. That’s why it’s important to be informed about common problems and how to prevent or address them.

In this blog post, we’ll take a closer look at some of the most common John Deere 6420 problems and offer tips for troubleshooting and maintenance. Don’t let preventable issues stand in the way of your productivity – read on to learn more!

John Deere 6420 problems

John Deere 6420 problems with mower’s air cooler

Let me tell you, as a John Deere 6420 owner, there’s nothing quite like the feeling of kicking back in your tractor seat on a hot summer day, with the engine humming along and the A/C blasting like a polar vortex. But when those air filters start getting clogged up with dirt and grime, it’s like a slap in the face from Mother Nature herself.


But fear not, my fellow John Deere enthusiasts. There are a few tricks to keep your Engine Air Cooler unit from conking out on you. First off, make sure those air filters are getting the TLC they deserve. Regular cleaning and replacement can go a long way towards keeping your A/C blowing strong.

If you’re still having issues, it might be time to take a peek at the suction line. Check for any blockages or leaks that might be impeding your A/C’s flow.

PTO Problems in JD 6420

chances are you’ve come across a PTO problem or two. It’s like the universe knows that you need to get that hay baled or those fields tilled, so it decides to throw a wrench in your plans – literally.

The symptoms are pretty straightforward: your PTO won’t engage, your back hydraulics are on strike, and your front reverse is giving you the silent treatment. And if that’s not enough, you might even get a light show on your dashboard, with warning lights, danger lights, and an exclamation point light just to really get your heart racing.


There are some steps you can take to get that PTO purring like a kitten once again. First off, inspect and repair the sensor – oftentimes, that’s the root of the issue. And if the sensor is beyond repair, you’ll need to replace it.

If the sensor doesn’t seem to be the problem, it’s possible that a pesky little fuse has blown. Don’t worry, it happens to the best of us. Just replace that fuse and get back to your regularly scheduled programming.

Excessive Fuel Consumption

Picture this: you’re out on your John Deere 6420, humming along to your favorite tunes when suddenly you notice something’s off. Your fuel gauge is dropping faster than a hot potato, and you’re pretty sure you’re not imagining things. Yep, your mower is chugging down fuel like it’s going out of style.

Now, don’t panic – this is a common issue with these mower models. But before you start cursing the day you ever laid eyes on that John Deere, take a deep breath and inspect the hydraulics. You see, constant hydraulic pumping is a notorious fuel guzzler, so it’s likely the culprit here.


First things first, check that valve – it might just be the key to solving this whole mystery. But if that doesn’t do the trick, there’s a chance your pump is discharging and dumping heat like there’s no tomorrow. In that case, it might be time to call in the cavalry – aka, a trusted mechanic or a savvy friend who knows their way around a mower.

So the next time your John Deere starts acting up and sucking down fuel like it’s nobody’s business, don’t throw in the towel just yet. With a little bit of know-how and a lot of patience, you’ll be back on that mower in no time.

John Deere 6420 shutting off problem

Have you ever fired up your John Deere 6420, only to have it shut down on you just a few seconds later? Talk about a buzzkill. But fear not this is a common issue with these mowers, and there’s a simple fix.


Grab your trusty tools and get ready to roll up your sleeves. You’re going to need to dismantle the fuel line that surrounds the tank and give it a good blowout. Yup, it’s as simple as that.

But wait, there’s more! It’s possible that something in the tank is being sucked through the outlet, so you might want to give that bad boy a good cleaning as well. After all, a dirty fuel tank is like a clogged artery – it’s never a good thing.

So the next time your John Deere decides to pull a fast one on you and shut down right after starting, don’t panic. With a little bit of elbow grease and some good old-fashioned know-how, you’ll have that mower up and running in no time.

Engine Shaking After Starting

Picture this: you’re all set to start mowing with your trusty John Deere 6420, but as soon as you hit that ignition, the engine starts shaking like it’s doing the cha-cha. Frustrating? You bet. But don’t worry, there are a few things you can do to get things back on track.


First off, it’s always a good idea to perform a starting choking check. Make sure everything is in its proper place and nothing is gumming up the works. If that doesn’t do the trick, it’s possible that something might be stuck inside the pump. But fear not – a quick inspection and cleaning can often take care of that issue.

If the shaking persists, there might be a fault with the electrical circuit, solenoid, or injector. At this point, it might be time to call in the pros. After all, you don’t want to do more harm than good trying to fix the problem yourself.

JD 6420 Engine Rev Problems

Have you ever been cruising along on your John Deere 6420, only to find that your engine revs suddenly hit the brakes? If so, you’re not alone – plenty of folks have reported this issue with this particular mower model.


To get things back up to speed, you’ll likely need to replace the sensor altogether. It’s a bit of a hassle, to be sure, but hey – better than getting stranded out in the middle of a field with no way to get going again, right? In fact, some experienced users even recommend carrying a spare sensor with you at all times, just in case.

So if you find yourself dealing with this engine rev issue, don’t sweat it. 

John Deere 6420 Power Quad Power Reverser Problems

Have you ever been cruising on your John Deere 6420, hit shift into forward, only to be greeted by a loud warning tone and a “N” on the display? Talk about a major buzzkill! This transmission issue is something that many 6420 owners have faced.


If you encounter this problem, the first thing to check is the reverser lever. If that’s not the culprit, it could be a faulty forward solenoid or wiring. The best way to get to the root of the issue is to have your codes read by a professional. Don’t let this problem reverse your productivity – get it fixed and keep on truckin’ (or tractorin’).

Final Thoughts

In conclusion, the John Deere 6420 is a powerful and reliable mower, but like any machine, it has its fair share of problems. From issues with the A/C unit, PTO, excessive fuel consumption, and engine shaking, to engine rev difficulties and transmission problems, these are common problems that many users have encountered.

While some of the fixes may be straightforward and can be handled by the user, others require a professional touch. However, regular maintenance and upkeep of the machine can go a long way in preventing these problems from occurring in the first place.

Overall, it’s essential to be aware of the potential issues that may arise with the John Deere 6420 and be prepared with the necessary knowledge and tools to handle them when they do. With proper care, this mower can serve you well for many years. So, don’t let these problems discourage you from enjoying the power and reliability of the John Deere 6420.

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