# Kubota L3710GST ROPS Electrical Problem



## Walt Henley (Mar 7, 2020)

I have an older L3710 glide shift that has been running just fine since I bought it a year ago. On cold mornings, I have to let the Glow Plugs turn off, turn the tractor for about 30 secs and then repeat the process again to get the machine to start. No big deal. Last week, I got on the tractor, turned it on, glow plug light went out, I turned it over. Turned the switch off, waited about 5 seconds then turned the switch back on. Lights on the dash came on dim, turned the key to start and they went OUT! I have replaced the key switch, cleaned the batter terminals and chassis side ground lug; check the slow blow fuse in the main power line. Pulled the wires off every relay on the dash and can't isolate the problem. When you turn the key on, the battery feed wire voltage to the B lug on the switch goes to one volt. I got some results by banging on the tab that holds the glow plug timer and relay. That helped for a minute, now it's completely dead. I am totally confused at this. I'm no stranger to electricity, I'm an electrical engineer. This one has me scratching my head. Does anyone have any suggestions?


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## BigT (Sep 15, 2014)

Howdu Walt, welcome to the tractor forum.

Dead battery?? Have you load-tested the battery?


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## Walt Henley (Mar 7, 2020)

BigT said:


> Howdu Walt, welcome to the tractor forum.
> 
> Dead battery?? Have you load-tested the battery?


Hey there! Battery is brand new. Sitting at 13.2 volts. In fact, I turned the tractor with it just before this mystery began.


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## Walt Henley (Mar 7, 2020)

Here's some additional information. I have:

1. Replaced the key switch.
2. disconnected all relays and controllers one at a time.
3. removed fuses one at a time.
4. removed grounds behind fuse panel, cleaned with file until bright metal and reinstalled
5. remove battery connections, cleaned and filed until bright reinstalled.
6. removed battery chassis connection, cleaned and filed until bright, reinstalled.
7. disconnected glow plug power feed.
8. AC terminal (Red White switched power) shows 250 ohms to ground?

Ideas?


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## Walt Henley (Mar 7, 2020)

AND, the glow plug relay doesn't energize when you turn the switch on.


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## BigT (Sep 15, 2014)

Walt, there may be a timer module that energizes the glow plug relay? Otherwise, it's probably controlled by the "black box".


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## Walt Henley (Mar 7, 2020)

There is a controller that manages the glow plugs after the relay energizes it. I disconnected both individulally as well as the glow plug power to eliminate them? I suspect the glow plug system somehow. It is the only thing beside the dash lights that comes on when the key is in the "on" position. But maybe not? Don't know. I'm bamboozled.


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## Walt Henley (Mar 7, 2020)

The relay is energized when you put the switch in the On position. It's not energizing right now.


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## BigT (Sep 15, 2014)

See attached parts diagram:

https://www.messicks.com/ku/93333?sectionId=233882&diagramId=507362

Item # 010 is your timer relay
Item # 020 is your controller
Item # 030 is your glow plug relay

If you are not getting power to the glow plug relay, my GUESS is the timer relay or the GP controller. If you will call the Messick's Parts Hotline : 877.260.3528, they should be able to tell you which is the most commonly replaced.

Alternatively, you might consider replacing the automatic glow plug system with a manual push button.


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## Walt Henley (Mar 7, 2020)

Turns out the main battery cable is bad. Bypasse . It with a jumper and the machine came right up! Bizarre. Apparently a resistive failure. Hence the behaviors.


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