I want to pass on some information and also solicit some comments on the glow plug controller (NGK 119650-77902) in my 4100. I was doing a lot of odd jobs around the place and had the tractor running for about 2 hours continuously. I shut down for a while while I hand loaded the FEL with some rocks, and when I went to restart all I got was the good old low battery clicking. I put a DVM on the battery and it was pretty discharged. After a quick charge it started right up and I again checked the battery voltage with the engine running. It was lower yet. I shut down and checked it again. It was a few tenths higher than when running. After checking the alternator output, which turned out okay I decided something was drawing down the battery faster than the 20 amp alternator could charge it.
It turned out to be the glow plug controller/timer, which is mounted on a vertical plate in front of the radiator. It turns out it was stuck closed, and the glow plugs were continuously drawing current - more than could be replaced by the alternator. They did not burn out because they are the dual element quick heating type that can run continuously without damage. Unplugging the controller resulted in normal battery charging.
Strangely enough, the glow plugs still come on when the ignition switch is in the "start" position, as normal. They just may not have a timed pre/post heat. I believe the controller/timer preheats the glow plugs for just a second as you pass through the "run" position on the way to the "start" position, where they stay on while cranking. It also may keep the glow plugs on for a couple seconds after the tractor starts and the key is back in the run position - the time being based on the ambient temperature (more in winter, less in summer). This helps avoid some of the initial smoking that occurs after a cold start (environmental thing). There may be some variation to this process, but I haven't found a reliable source that knows anything about how this works.
My dealer didn't have the $80+ part in stock so I decided to leave it unplugged for now. The JD mechanic said many do the same. I have no problem starting, since the glow plugs still work during cranking, and if it is very cold, I cheat by pulling the PTO switch out (to prevent starting), turning the ignition to "start" to begin a quick two second preheat of glow plugs, then I push the PTO switch back in to allow the starter to crank. All is well.
This may well explain why so many owners of this series tractor (and similar Yanmar marine engines) have charging problems and can't find anything wrong with the alternator, battery, relays, etc. Speaking of marine engines - the controller is available from marine dealers for about $25 less than from John Deere. Go figure.
It turned out to be the glow plug controller/timer, which is mounted on a vertical plate in front of the radiator. It turns out it was stuck closed, and the glow plugs were continuously drawing current - more than could be replaced by the alternator. They did not burn out because they are the dual element quick heating type that can run continuously without damage. Unplugging the controller resulted in normal battery charging.
Strangely enough, the glow plugs still come on when the ignition switch is in the "start" position, as normal. They just may not have a timed pre/post heat. I believe the controller/timer preheats the glow plugs for just a second as you pass through the "run" position on the way to the "start" position, where they stay on while cranking. It also may keep the glow plugs on for a couple seconds after the tractor starts and the key is back in the run position - the time being based on the ambient temperature (more in winter, less in summer). This helps avoid some of the initial smoking that occurs after a cold start (environmental thing). There may be some variation to this process, but I haven't found a reliable source that knows anything about how this works.
My dealer didn't have the $80+ part in stock so I decided to leave it unplugged for now. The JD mechanic said many do the same. I have no problem starting, since the glow plugs still work during cranking, and if it is very cold, I cheat by pulling the PTO switch out (to prevent starting), turning the ignition to "start" to begin a quick two second preheat of glow plugs, then I push the PTO switch back in to allow the starter to crank. All is well.
This may well explain why so many owners of this series tractor (and similar Yanmar marine engines) have charging problems and can't find anything wrong with the alternator, battery, relays, etc. Speaking of marine engines - the controller is available from marine dealers for about $25 less than from John Deere. Go figure.
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