Burned 4WD Solenoid

[bxray]

Diode polarity. The cathode is negitive.

 

[jericho]

I see it the same way as BXRAY. Right now I've got to turn my attention to our FIAT crawler with charging problems.
Will get back to the Kubota in a day or two.

Thanks to all of you. Be back soon with follow-up.

 

[bxray]

I was thinking if you could try putting power on the coil with the valve assembly off the tractor.
Like pictured.
On a bench?

This way there is no hydraulic pressure.
Cycle it a couple of times and then leave the power on.

Ray

 

[jericho]

Thats next bxray. I like putting power straight to the coil. What I'm going to do this week is switch the position of the two coils. Lets see if the coil that did not get hot where it was ... does get hot when I put it in the spot where the other coil got hot.

Stat tuned to this station.

 

[bxray]

Ok.
Just to confirm.
Try it with the valve body off the tractor so the ports are open.
This way there is no back pressure.
This is the new valve?
If it does not get hot then it will be the orfice or other fluid path.

Ray

 

[jericho]

Yes.. The new valve has the only good black wire coil.

 

[jericho]

Well I had all three valves (two old ones and the new one) ON THE BENCH...NO RELAYS...NO DIODES. Just running 12 volts from a battery.

Every coil gets hot! But the black wire one (the only good 4WD one left on the brand new valve) gets real hot, real fast. I'm o.k. with solenoids getting a little hot but I just don't want to keep buying valves because that coil keeps burning out.

I switched the positions of the green and black wire coils... It looks like it's a position issue since the green wire one gets hot real fast in the black wire position

I could try an ammeter but I don't think that will tell me anything that I don't already know.

Going to LA in the near future. There is an outfit down there that winds coils. I might run it by them.

Thanks for your suggestions.

 

[ShaunRH]

That sounds like a shaft alignment issue. If the permanent magnet gets stuck in just the wrong area, it will work the coil hard.

I still haven't heard from anyone else with this unit, it may be a problem with the entire unit. Have you talked to a Kubota dealer/mechanic about it? Maybe there's a notice out on the issue.

 

[jericho]

Yes... The local dealer was the first place I went... Talked to the parts guy and he said he had sold one in the year that he had worked for the dealer. The service manager let me talk to a mechanic and he said to check diodes.

Kubota in Torrance had no answer.

How can all three valves have internal shaft problems that make the coil hot??

Why is it so hot on a bench test? I'm probably going to do what Wolfman said and change diodes and relays??

 

[1966plowboy]

O.K. I'll post a picture as soon as I can.

Meanwhile to answer a couple of points:

1. My understanding is that DC coils don't get hot if they don't get the solenoid to shift all the way, but AC coils do.

2. I think I eliminated the question of a diode being involved when I simply energized the coil directly from the battery with a two-lead jumper. I started to get hot right away, just like it does when I energize it hooked up in the normal system.

Jericho, I also have a M8200 Narrow with the same issue. I replaced the solenoid about 18 months ago and now it is out again. haven't used the 4WD very much. It will blow the fuse instantly. any luck with repairing yours?

 

[JP_Austin]

Odd one. If the coils are the same ohm range then I would expect them to heat up exactly the same. As the coil heats up if there is an internal weak spot in the insulation I could see it going very hot and not working well on the valve. I suspect that the failing coil has weak insulation and it's worse when it get hot.

In DC solenoids it does depend which way the current is flowing as far as the magnetic field direction. So if wired up backwards I could see that causing a lot of issues.