modulating valve

[scarecrow]

I'm trying to track down the problem with the PTO on my tractor everything seems to be fine as far as the modulating valve this is an electrical valve with some sort of coil on top i have taken it out to have a look and can't figure out how it works has anybody got any idea on how to test this valve
here is a link to the John dear parts catalogue might give you a better idea
http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet_Alt

 

[madkayaker]

need a part number the link just goes to blank results. (Even then i haven't got a clue what your on about)

 

[scarecrow]

here is a picture instead

the thing that is baffling is there doesn't seem to be any moving parts the wires just plug-in at the top it says on the parts list that this is a coil the problem is the tractor is was blowing fuses but now it has stopped but the pto isn't working probably best to just get a mechanic

 

[madkayaker]

sounds like somethings burnt out some where (maybe)

 

[wyn]

Can you put 12v to it and hold the valve to see if you can feel it clicking.
The spool part of the valve must be inside, so there should be some sort of drilled holes in the areas between the o rings.

Is the problem somewhere else like damaged wiring?

 

[scarecrow]

I connect it back up to the tractor and switched it on and off and there was no clicking
there is holds between between the o rings I've checked the wiring and it seems to be okay and there is power going into the valve

 

[paulmowers]

Hi Scarecrow

I would guess you need a new one, as you say power is getting to the valve but it doesn't click when operated, and as it originally blew fuses, pointing to a short internally, and now it doesn't blow fuses then i would guess its now open circuit. Can you check with an ohm meter / continuity tester on the coils terminals? If theres no contact then you do need a new one.

atb paul..

 

[wyn]

It does sound like the coil is likely to have had it.

I expect they only sell it as a unit.

The fuse might have been blowing because of something wrong with the coil.
After a few fuses the coil is damaged so there is no electrical continuity so the new fuse won't blow anymore. And the valve won't work either.

That's about all i can think of.


I wouldn't reccomend it........... but If you were really desperate you might be able to knock the coil off the valve with a hamer and tie a bit of string to the end of the valve to operate it

 

[MrFluffy]

Test it with a multimeter across the terminals set on resistance, if it reads open circuit the coil is tatered. If it doesnt, odds are its stuck mechanically somehow and MAY free up with some cleansing/maybe a ultrasonic clean...

 

[scarecrow]

Thanks for all your help guys to be honest I'm relieved that that's all that might be wrong ill give the dealer a ring tomorrow and see if I can pick up the peace as far as I know you can buy of bits separately tanks again

 

[scarecrow]

Test it with a multimeter across the terminals set on resistance, if it reads open circuit the coil is tatered. If it doesnt, odds are its stuck mechanically somehow and MAY free up with some cleansing/maybe a ultrasonic clean...

How do I do that not sure how to test and what would I need to clean it ultrasonic

 

[Bigjoe]

You could try a specialist fuel injection center (ie Bosch or similar) you should be able tofind one in yellow pages/Thompson local etc.

Or jeweller but they might not like your valve in the jewellery tank!

Joe

 

[scarecrow]

Iv been googling I think I know how to set the multimeter to resistance and if there is no reading then it's open circuit I think I'll give it a try tomorrow and see what happens probably easier to get a new one than trying to get some jeweller and I need to inspect is ultrasonic cleaner

 

[zzr1200]

SC, can you remove the coil from the spool by undoing a threaded collar or nut, don't hold the spool in a vice tight???

PS. some coils earth via the spool, some dont and require an earth wire to complete the circuit.

 

[bogbushcricket]

Hi Scarecrow,
the valve will be seized in the solenoid with rust.
If you remove the nut on the end and grip the valve with pliers or vice grips between the o'rings (taking care not to damage the lands that the o'rings are in or making the valve oval by gripping it too tight) then you should be able to rotate the valve very gently and carefully and remove it from the solenoid.
clean it up with emery cloth grease it and put it all back together it may work.
If it's been blowing fuses previously then the solenoid may be knackered and you will require a new one. If it's a four wheel drive then the front wheel drive solenoid is the same as the pto one and you could swap them over to test the electrics.

Hope this helps

BBC

 

[aero]

I'm always chnaging this type of valve on aircraft, not this exact sort, but ones that work similiar. They are a total pain and often go wrong.

When it says its a modulating valve it means it can hold any position between open and closed. So it won't click when you put power on it, unless it slams full one way.

In theory the way to test the electrical side is with a multimeter. However in my experience you can have these test OK, but simply don't work. One reason for this is the internal surfaces are ground to exacting finishes and fits which means even a speck of dirt can damage the valve and stop it working.

Replacement is the cure. Change the hyd filters at the same time

 

[snowcat]

If its iffy it may need replacing, the problem is if there not engaging properly they can can destroy the lanin on the clutch, trust me thats not something you want to buy....2K and a 3 day split.....

That a 69 series JD isn't it, Its a job to test circuits like this, depending on the age without some know how and a laptop, per example, 60 series New Hollands would cut the PTO for no reason, after recalling PZM valves etc, they found it to be over voltage overheating one of the management modules, solution was to upgrade the software drop the volts increase the amps..... CAN bus machines have all kinds of wired and wondeful ways..

BTW they don't normally offer any problems as far as iv heard.......

It may be as well to have it looked at by a dealer....could be as cheep in the long run.....

 

[scarecrow]

I took a coil off the valve and and swapped it with the coil off the differential lock which is identical and the PTO works fine
So I think it's just a new coil and I will replace the o rings as well because it's been in and out a couple of times
I tested the coil with the multimeter set on resistance and was getting no reading so I'm presuming the coil is bugger I'm hoping that was because the coil was old and not some other problem leading to the destruction of the coil

 

[snowcat]

a new unit then and jobs a goodun stroke of luck that, I think that era of JD was still quite simple, which IMHO is a bonus, The fly by wire is all a step to far for my likeing... I had a debt to repay last week, for a local farmer (actually I'm sure the farms just a front for all the industrial units he rents), he had me running about on road work moving plant about, he has a couple of new JD running all the auto steer stuff, and me on a Fendt Vario, like mission control that, but where would you start if you had a problem on a machine like that......

Same guys taking me up to LAMMA show next week so I think it could be an anorak's day out...

 

[scarecrow]

I used know my way around the older tractors as they were pretty straightforward but everything is electric in the new ones my John deer is a 6200 which isn't too bad but I've seen a few of the new ones just trying to figure out how to drive could be a problem and if you think there bad you should try driving a new forestry harvester (space shuttle stuff)

I ordered the coil today they should have it by Monday the thing that surprised me was just or hot the coil get when its switched on i presume this is normal as the coil on the differential valve also got hot

Thanks again for all your help ye have saved me a small fortune by solving this instead of having to get in a mechanic Malcolm should have some sort of tips jar so anybody who gets help on the forum could put a few Quid in
in if they wanted to