# Trying to understand wiring diagram for G1800 (G1700?)



## RNA (8 mo ago)

I was at a party at the weekend where they had a Kubota G1700 that wouldn't start. As I had a multimeter I offered to help knowing only a few basic concepts. We had fun poking around cleaning switches and servicing the starter motor etc. There was no internet in this area so we didn't have a wiring diagram to shed light on the electrical system.
It ended up that is was a cable that needed greasing to fully activate a switch. 
Upon returning home we investigated some wiring diagrams and found the G1800 to be most similar. 

Being the inquisitive type, I wanted to gain a full understanding of the electrical system so I decided trace out with colours to help to understand what is going on. But I have a couple of questions with regards to some wiring.

Here I have shown the live +12V.
Is it correct to say ;
1 The output from the Regulator is to charge the battery via the middle 20Amp fuse?
2 Another feed is tapped off from the battery 12V through the top 15Amp fuse which then feeds into the Combination Box? Does this supply a voltage that the combination box uses to switch on and off?









Then you turn the Key switch once and this passes 12V to the dash, sensors, gauges and powers the Confusernation Box.








One more turn of the key and the 12V is also sent to the glow plugs and to an input on the Confuser.








And one more turn of the key sends an input to the Confuser which in turn sends a voltage to the starter motor providing it is happy with the safety switches.








Here is the full colour trace out for anyone interested.









And my final question is what are the differences between this G1800 wiring diagram and the G1700?


----------



## jknc (5 mo ago)

Hello...
I dont know if you have your question answered or not, but I stumbled upon it while looking for info on my G1800. You dont have many questions, just statements but to me it seems by those you have a pretty good grasp of what is going on with this machine. Let me try to help you:
First, your questions:
1: Yes. The combination box has nothing to do with charge circuitry.
2. Yes, but you also have the fusable link which is by the starter (at least on my G1800)
2b. Yes, more or less. Diesel takes no power to operate. It does need power to shut it down (operate the fuel shut off for 10 seconds). The combination box is really nothing more than for safety and for the glow plug timer.
Final question: According to my service manual, the combination box is the same for all 3 machines: 1700,1800, 1900. Only 2000 is different.

About the confuser: It requires power all the time. Your understanding is correct on how it starts the tractor. Let me add since it is a diesel, it actually needs power to turn the machine off too. It activates the fuel cut off on the injector pump for 10 seconds when:
-You turn the key off
-You exit the seat when the PTO lever is engaged
Best of my recollection, it only monitored the brake petal for the start circuit. Mine is broke, so I cant confirm(more later). 
The confuser (really combination box as Kubota calls it describes it better) does not have alot of intellegence and I dont believe it's a real computer, as I redesigned it with just 3) 555 timer circuits and some mosfets. Mine went bad, and I'm not paying $250 for no more than that thing does. It's nothing to make the circuit and pot it and 3d print a new box - mine looks almost as nice as Kubotas.  My seat is in decent condition, but there is a short in the 12v to ground and it about caught fire, so I don't have use of the seat safety anyway, which i just left jumpered. My problem exists in that it will not turn the tractor off until it warms up. Sometimes the safety works on mine, sometimes not - the box is just toast. I ran a wire from the ignition right to the starter solenoid as the box stopped working the starter long ago. I did put a seat safety in my designed circuit, as I do intend to fix my seat. As far as what I designed:
-1x circuit for cut off, 555 in monostable mode, input with and gate between seat switch low and PTO high and ignition on->off (some other misc glue circuitry, but you get my point
-1x curcuit for glow plug indicator, monostable, 5 second set with RC - Logic: turn light on when switch on glow and off after 5 seconds. (set according to experience and service manual
-1x cutoff circuit, monostable, triggered by key on ->off, used transistor to activate active low-> high pulse to activate circuit. This also triggers the latching kill circuit:
-1x latching power saver circuit - triggered by turning key off->on.

I built this because I was tired of activating the fuel cut off by hand until my tractor warmed up. And I wanted it back to stock. I built it a couple years ago, and I drew a schematic somewhere but not sure where. I built it on perfboard, so I have no real PCB board layout as I was only making one. So everything I told you above is by my memory from quite a few years ago, so forgive if there is a small error, but I'm certain there were not more than 3 main circuits and no computer/MCU was needed for something so simple - and I doubt Kubota did either as they just called it a "combination box" and not an ECU.

Good luck fixing yours!


----------

