Automatic Glow Plug Operation (L4200)

[Jay4200]

I've always wondered if my glow plugs are working on my L4200. It supposedly engages the glow plugs automatically if they are needed when you turn the key on. I have not used my tractor in the winter until this year, so I don't have much experience with the operation. I have noticed the glow plug light going on when it is cold (30Fs), but it only stays on for a couple of seconds at most. Would engaging a glow plug for 2 seconds even do anything?

My tractor has always started up after a few seconds of turning regardless, but I worry about getting it going when it is really cold later in the year (if something isn't working right).

JayC

 

[bilrus61]

My L4200 would glow longer in cold weather. It never failed to start right up. If you worried just turn the key on and then off and on again to get it a extra boost. At about 500 hours my L4200 glow plugs got a mind of their own! They would go off and on anytime and in any weather. I called Kubota and they said it wouldn't hurt the engine. It was a module that gets funky in them and turns it on and off for during use. My L4200 started great all the way down to 20 degrees. When it was colder than that I had the sense to stay in the house!

 

[KennyV]

I've always wondered if my glow plugs are working on my L4200.
... it only stays on for a couple of seconds at most.

JayC

That's the way they work.. and like bilrus said, when it's really cold give it another cycle or two...

......At about 500 hours my L4200 glow plugs got a mind of their own! They would go off and on anytime and in any weather. I called Kubota and they said it wouldn't hurt the engine. It was a module that gets funky in them

That's the controller, there is a diode that fails in it ... and causes intermittent problems... It will over time give your glow plugs additional hours and lead to their failure, but that's going to take a while...
That controller is inside the dash near the relay. and it's a little over $70...
Someone on here was going to just do away with the auto system and put a push to heat button on... don't know if it was done or not. That would be the simplest fix... just have a push button actuate the relay... KennyV

 

[Jay4200]

That's the way they work.. and like bilrus said, when it's really cold give it another cycle or two...

'Kay - I started up the beast Saturday, after sitting for a couple of weeks, and after a nice freezing cold night. I turned on the key and the glow plug light stayed lit for about 5 seconds. I turned the key, and it started about halfway through the first crank. "ShhhVOOOM..." It was a bit clanky for the first second or two, which I suppose isn't too abnormal - and it sure starts good for a 2500 hour machine.

JayC

 

[Jay4200]

'Kay - I started up the beast Saturday, after sitting for a couple of weeks, and after a nice freezing cold night. I turned on the key and the glow plug light stayed lit for about 5 seconds. I turned the key, and it started about halfway through the first crank. "ShhhVOOOM..."

So, it is yesterday (3 weeks after starting this thread), and I started up my L4200 after it was sitting a week, just to stir it up for a minute or so. It was cold, but not outrageously cold... ~25F or so. I got no glow plug light when I turned on the key. The tractor cranked for a long time, probably close to 10 seconds, before kicking over and firing up. It seems that my glow plug automatic thingie crapped out on me. Unfortunately, I don't know how to diagnose and address that system. Any and all suggestions and/or directions would be appreciated.

JayC

 

[KennyV]

Hello JayC...
There is a relay and a controller UNDER the removeable dash.
They are both on the right side, mounted together.
The controller is the normal thing that fails its around $70...
You could just replace it with a push button to apply 12 volts to the coil of the glow plug relay... (thats what I will do if my controller fails again).
Heree is a picture of the controller that Kenonf posted... http://www.tractorbynet.com/forums/...-controller-l3600gst-glow-plug-controller.jpg

If you need the wiring diagram it's here... http://www.tractorbynet.com/forums/kubota-owning-operating/134518-glow-plug-wiring-help-needed.html
At post #6...
KennyV

 

[KennyV]

After looking at the wiring diagram again... You will not apply 12 volts to the glow plug relay coil... You will apply ground to the GP relay coil ... it has 12 volts applied whenever the key is on, the controller normally supplies the ground for the coil... so if you were to replace the automatic controller with a push button you would only have to apply ground with the push button ... easy change over... KennyV

 

[mcd176]

After looking at the wiring diagram again... You will not apply 12 volts to the glow plug relay coil... You will apply ground to the GP relay coil ... it has 12 volts applied whenever the key is on, the controller normally supplies the ground for the coil... so if you were to replace the automatic controller with a push button you would only have to apply ground with the push button ... easy change over... KennyV

Thanks for the info Kenny, Ill keep this in mind if mine fails, I usually cycle my key 3 or 4 times in the freezing cold and it fires right up.

Mike

 

[jonyyuma]

Wondering if any one has opened the relay after failure, in order to see if it can be repaired...Ie." the diode failed"? Personally I have no trouble reverting back to a push button and counting. My tractor has the reversing igniton switch activation for glows.. Jy.

 

[Jay4200]

I figured I'd revive this thread - I FINALLY addressed my dead glow plug problem this past weekend after it being broken for two years. Relay is good (opened it up - nice relay), thermistor was good, so it had to be the controller. I pulled the controller out, then used the existing socket to bypass the function. I shorted the center two leads together on the controller's 6-pin socket using blade connectors ('out to relay' and 'out to indicator light'), then ran that line through a momentary switch to ground. Push button when key is on, glow plugs are activated and yellow indicator light goes on. Sweet. If I ever want to replace the module, I just pull out the blade connectors and plug a new module in. I can't imagine I ever will though...

I still don't understand what the diode-or circuit (that come out to the center pins) does in the module - rather than just shorting them together - I suppose it would prevent a potential back-feed through the bulb, but so what? I don't see it happening. It seems that the diode-or would transfer the inductive kick from the relay energizing coil (and it does give a kick - enough to arc) onto the internal transistor, rather than to the light bulb, which seems exactly what you don't want to do. Perhaps there is a non-shown zener on that pin in the controller? Maybe a snubber of some kind? I was thinking of putting a cap (like a 0.1uF) across the switch - that act as a snubber with the bulb and would absorb the relay's inductor energy when the switch is released. What do you think?

JayC

 

[KennyV]

Excellent JayC...
I have always thought I would do just that if my controller ever failed... again.

You likely don't need an RC snubber, if you are concerned about the flyback, just a simple diode across the relay coil will catch it... KennyV

 

[Jay4200]

Excellent JayC...
I have always thought I would do just that if my controller ever failed... again.

You likely don't need an RC snubber, if you are concerned about the flyback, just a simple diode across the relay coil will catch it... KennyV

Super simple, once I traced it out (using your schematic, incidentally). A diode would surely catch the flyback pulse - turns out there isn't a whole lot of energizing current - something like 150mA for a typical automotive relay. I think the light bulb probably does a fine job at snubbing the flyback all by itself, since I have the coil and bulb shorted together. I may wire in a diode-or network with a snubber diode, just for the heck of it, if I get the urge to take off my dashboard for some reason . I just can't believe I finally got a round tuit!!

JayC

 

[KennyV]

It should be a lot happier starting with glow plugs this winter... KennyV

 

[nhart]

Just purchased a used L4200 GST look to be having a similar problem. My glow plug light stays on, it will randomly go out, but most often is on. Should I just bypass the controller with a switch, or replace the controller?

 

[KennyV]

The controller will cost about $75 US....
Or you can go to the glow plug relay and wire in a momentary (push button or spring loaded) switch... wire it to apply Ground to the coil of that relay.... It will work perfect with just a few seconds held on when temp is below freezing. KennyV

 

[Jay4200]

The controller will cost about $75 US....
Or you can go to the glow plug relay and wire in a momentary (push button or spring loaded) switch... wire it to apply Ground to the coil of that relay.... It will work perfect with just a few seconds held on when temp is below freezing. KennyV

I've been using my big black button for 3 years now - works awesome, and after a 5 second push, my tractor now starts instantly down to way colder than I will dare go outside. The module shorts the light and relay energizing coil to ground - other end of both is at 12V, so I replace the module function with a simple switch that is connected to ground. I never changed my original configuration, I simply shorted the relay coil and light module inputs together (I used the existing module socket and simply plugged the wires in via blade connectors) then both get grounded through the big black momentary switch on my dash.

 

[Jay4200]

Just purchased a used L4200 GST look to be having a similar problem. My glow plug light stays on, it will randomly go out, but most often is on. Should I just bypass the controller with a switch, or replace the controller?

If your light is staying on, that could be a bad thermistor or a blown transistor in the module. If the light is on, you should assume that the glow plug is too, and having the glow plug energized all the time can't possibly be a good thing. Pulling out the module will disable both light and plug. I'd bypass it with a switch - directions on previous page.