The range for the John Deere 6420S from the 6020/6020SE series is wide: more than 700 parts, with electrics, trailer couplings and lighting at its core.
More than 700 parts fit the John Deere 6420S, and the sections that follow concentrate on the engine and what surrounds it: O-rings and gaskets, the thermostat, hoses, the alternator and the starter motor. Alongside those you will find work lamps, headlights, a ball drawbar and external plates for the clutch.
The thermostat decides how quickly the engine warms up and whether it holds its temperature. For the 6420S there is a thermostat together with the matching regulator housing gasket. Around the cooling system you will also find hose sold by the metre and sensors such as an engine oil pressure sensor.
The multi-rib belt drives the alternator and water pump, and on tractors with air conditioning the compressor as well. That is why there are belt kits for machines without air conditioning and separate multi-rib belts for those with it.
Tip: check whether your 6420S has air conditioning before ordering a belt, since the length depends on it. And never refit a thermostat without a fresh gasket. An old gasket that has already been compressed will nearly always weep once it is tightened again.
A tractor that is slow to turn over does not always have a failed starter. Check the battery and the earth strap first. If the fault stays, the starter motor and alternator for the 6420S are both on this page. Because the alternator sits in the same belt drive, a replacement is a good moment to look at the condition of the belt.
Seals and bushes for various points on the tractor are here, as are external plates for the clutch. Work lamps and headlights, some from HELLA, light up the job after dark, and a ball drawbar covers the rear. Further parts come from GRANIT, MAHLE, Sauermann and Wabco.
With the external plates, replace a worn pack as a whole rather than a single plate. New plates next to old ones spread the pressure unevenly, and the clutch starts to slip or snatch.
The 6420S belongs to the John Deere 6020 series. Note that the 6420 and the 6420S each have a separate page, so check the type plate to see which one you own. When in doubt, the number on the old part settles it.
Other tractors from the 6020 series with a page of their own:
The 6520 and 6020 complete the series. For every model the brand offers, go to John Deere parts.