Bad news big repair

[clewis]

The ECU reads the air and water temp sensors and they are both part of the glow plug wiring circuit and it has been stated that if the relays are bypassed, the tractor derates itself.
So how do you bypass all that and “simply install a switch”?

If you measured the resistance of a glow plug, and flipped the glow plug hot wire to a resistor with the same value, you can probably trick the ECU into thinking that the glow plug is still in circuit and the wiring for all of the relays is intact. Then you're able to control the glow plug with your own switch through a new supply wire, and the ECU has no way of telling that you're cheating, tho Kubota might deny warrantee service. It's *entirely* possible that the ECU is supposed to handle the glow plugs entirely on its own, and/or designed to NOT allow glow plugs above 41F. The former is the general move towards "improving the user experience" (gag) by removing as many buttons as possible. As to the latter, durn it, if there's a button, I *expect* the button to do what it's told unless it's going to kill me. Hitting the Park button at 70mph is something that I'd expect a car to refuse.

Your best bet to is to put in a direct query to your Kubota service guy as to whether your tractor model and year ECU is *supposed* to inhibit glow plugs above 41F. If they don't know or seem uncertain, get Kubota itself to answer that question.

 

[lilranch2001]

In my (never to be) humble opinion, to have to perform and jump through all these hoops to get a tractor to run correctly, some engineer has gone way, way, way, beyond good engineering!

 

[butch5875]

Would it be easier to install an engine block heater and forget glow plugs?

 

[K5lwq]

The ECU does not care about the glow plugs obviously. The tractor is working now with the glow plugs disconnected because the relay is not Energized. The OP does not have to worry about fooling the ECU.

 

[RickB]

Big companies really have special funds for so called "good client", who bought more than one product, was/is loyal in after sales programs, recommended the brand name to the other clients...

Sometimes it works if the machine gets expensive failure even after more than 3 years.

Goodwill claims are reserved for original owners.

 

[priberc]

Purchased my M135X in warmer months almost 3 years ago (April 2019). Never thought to see if the glow plugs worked. They actually won’t work if it’s over 41*.
Last winter, I realized the glow plugs weren’t working. Ohmed out wires, looked at wiring for mice damage, water damage, bad grounds, etc. Ohmed out wiring. Thats when I learned the glow plug system in larger kubotas is more complex than I thought. All 4 glow plugs passed electrical testing.
The glow plugs have 2 sensors one for air temp, one for water temp. The ignition switch is also part of the circuit. Then there are 2 relays and a fuse. All of this is controlled by the ECU. Last winter, I replaced
Key switch
water temp sensor
air temp sensor
both relays
fuse

Still no glow plugs. With nothing left to replace or test, I succumbed to a very reputable Kubota dealer. They basically did all the same things I did and replaced one of the new sensors I had already placed.
Still nothing. They called Kubotas double secret probation hotline and Kubota thinks it’s the ECU.

ECU price $6000
ECU Not returnable and no guarantee it will fix glow plugs.

So I’m out of answers. Any thoughts on other possible avenues to pursue?

Just a thought here but I have a frost plug style block heater in my M85 Mahindra. -10-15c [5-15F] plug it in.....wait for about 3 hours and the manifold heater does not even cycle. An awful lot of electricity can be bought for 6k. If that would work for what you use the tractor for in the winter it is both cost effective and IMO works just fine. As a matter of fact I would be surprised if you could not get all you need from Kubota.

 

[ArtMech]

Goodwill claims are reserved for original owners.

I've seen Hay Dude owns more than one Kubota product. But don't know if he is original owner of all that equipment or not.

 

[RickB]

I've seen Hay Dude owns more than one Kubota product. But don't know if he is original owner of all that equipment or not.

Well the last M135 was built in 2014 and he said he bought the tractor 3 years ago. I'll go out on a limb and say he's not the original owner of this tractor. Whatever else he owns is irrelevant.

 

[Lockport]

Block heater

 

[ArtMech]

Well the last M135 was built in 2014 and he said he bought the tractor 3 years ago. I'll go out on a limb and say he's not the original owner of this tractor. Whatever else he owns is irrelevant.

Maybe. Just sales date (especially in tractor business) could be way later, than production date.