M4950 ignition switch wiring

[Ozcar]

Hi orangeistas:

My just-acquired M4950 has incorrect wiring set-up to the ignition switch: the previous owner told me he had replaced the switch before I bought it but 'had misplaced the wires a bit'.

Well, yup. There is no power in any position going to the instrument panel and the glow plugs only get power when the engine is actually cranking, which means that starting is pretty much impossible if the ambient temperature is under about 30C (86F) and even then it's a long period of cranking with a fully-charged battery before it will finally fire properly and start to run.

While I await delivery of an Operator's manual and Workshop manual, (probably three weeks at least to get here to Oz) I would like to get the damn thing running.. so does anybody know the proper wiring arrangement for the switch?

Hoping... hoping...

 

[GeoHorn]

My M4700 glow plugs also are energized during start. I’m understanding that is normal.
The key is turned Left to preheat the glowplugs. Off is center. Run is right. Start (and glowplugs) are spring-loaded full-right.
You might find a WSM with schematic online at kubotabooks or kubotamanuals

 

[Dave_eng]

Since on line manuals are non existent, suggest you start by providing a list of the terminals on the back of the key switch.

Kubota tends to follow a certain convention in both terminal designation and wiring color so it may be possible to reference other models of the same vintage to see the color convention they follow and then make suggestions.

Also need to be certain the new switch is actually a Kubota switch as sometimes owners grab anything that claims to be a key switch.

If I understand what you have said, the engine will crank when the key switch is turned to start. Please confirm this.

Dave

 

[whitetiger]

Since on line manuals are non existent, suggest you start by providing a list of the terminals on the back of the key switch.

Kubota tends to follow a certain convention in both terminal designation and wiring color so it may be possible to reference other models of the same vintage to see the color convention they follow and then make suggestions.

Also need to be certain the new switch is actually a Kubota switch as sometimes owners grab anything that claims to be a key switch.

If I understand what you have said, the engine will crank when the key switch is turned to start. Please confirm this.

Dave

Here is a pdf of the wiring from the operators manual.

 

[Dave_eng]

The proper key switch will have three electrical connectors to avoid any mis wiring when replacing the switch.

Part # 35822-75180 for $23

Dave

 

[Ozcar]

Guys - you are great people! Thanks a million for all the info and especially for the wiring diagram.

Sorry about the slow response - I have been enmeshed in curing a leaking JD 410 Backhoe transmission (Handy Household Hint: do NOT do this if you have made a resolution to not terminate with extreme prejudice any designers of this class of equipment this year you may casually meet, unless you have a lifetime oversupply of Prozac Magnum-strength). It only took me the most part of two working days to isolate the problem to two weary o-rings and replace them.. and the stitches should be out in the next fortnight.

Yes, mine is a genuine Kubota switch with the three connectors, and there was only one rogue extra wire attached to that.. which does not mean that the wires have been put onto the correct terminals. But I can deduce that from the pdf.

I went chasing the more obvious wires (carefully: in Australia, dark confined spaces such as behind instrument panels can house dangerous critters, though it is untrue that every spider we have is deadly poisonous - some of the big ones just bite your leg off and wait for you to bleed to death).

I found that firstly, someone has liberally sprayed engine block etc. with the Kubota blue paint, overcoating much of the wiring, and then - quelle horror - I found one of those nests of wires, mangled connectors, broken case self-resetting fuses and anonymous wires twisted together and wrapped in lousy tape that every old tractor etc. has as a special guest.. hiding behind the power steering pump. Cue 'Oh No, not AGAIN' from Spaceballs.

Ho Hum... but thanks to the advice from everybody, I am way better armed to start to sort it out!