Automatic Glow Plug Operation (L4200)

[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.