Draft control problem.

[RegL]

A while back, on my 1430, the draft control stopped working. After some time I isolated the problem to the adjustable hydraulic valve in the draft control unit. Terry doubted that was the trouble and Keith said he couldn't remember ever sending out a replacement for one. I ordered a new one anyway, for close to $200..
The replacement is not exactly the same as the original but the draft control is working, but only when I crank the valve all the way down. I'm going to call Keith back this week to see if I can get the correct valve. Just wanted to share and wondering if anyone else has had draft control problems.

 

[J_J]

What implement are you using draft control on?

I have a 1445 and I don't have draft control.

Draft control is normally associated with tillage.

 

[woodlandfarms]

I have Draft on the 1850. It is used for slope mowing. It raises the mower deck up off the ground so that you get more weight on the front wheels. I think mine is a bit buggy. I should tear it down and clean it.

My feeling is that it provides X amounts of pressure to the lift cylinders on the arms, keeping them "bouyant".

 

[ponytug]

You do have to adjust the draft on an attachment by attachment basis. My understanding is that it sets a particular pressure in the lift cylinders. Since it maintains the pressure under dynamic conditions, the attachment still "floats" with changes in terrain, but with a critical difference. In "float" mode, all of the weight of the attachment rests on the attachment wheels. In draft mode, all but a small amount of that weight is borne by the tractor, thereby increasing the weight on the tires and improving traction.

For the bigger mowers on slopes, it is very useful to transfer all but a small amount of weight to the tractor.

I only use it for my brush mower.

If you have to crank it all the way down, I would have the concern that the auxiliary pump is not producing sufficient pressure. Does the behavior vary by engine RPM?

All the best,

Peter

A while back, on my 1430, the draft control stopped working. After some time I isolated the problem to the adjustable hydraulic valve in the draft control unit. Terry doubted that was the trouble and Keith said he couldn't remember ever sending out a replacement for one. I ordered a new one anyway, for close to $200..
The replacement is not exactly the same as the original but the draft control is working, but only when I crank the valve all the way down. I'm going to call Keith back this week to see if I can get the correct valve. Just wanted to share and wondering if anyone else has had draft control problems.

 

[J_J]

Put a gage in that valve and you can see what the pressure is and let you maintain same.

 

[ponytug]

Dear RegL,

If it is fed from the drive pump (tram), how do you adjust the lift levels?

I will check mine. I don't think that is how mine is plumbed.

All the best,

Peter

 

[woodlandfarms]

Mine is off the lift tilt dump circuit. Actually I don't think it is possible to work off the tram. I am in la so can't help much more.

 

[RegL]

I'm not very good at this, but let me try to explain ( after some time trying to trouble shoot) how I think this all works.
First just the physicals. Woodlandfarms posted a pic of the draft control unit. Thanks. connected to it are five hoses. two come from either side of the tram pump. Mine are actually teed off the wheel motor circuits. One hose goes to the hydraulic tank. and two lines go to a splitter block in the front of the tractor for the lift cylinders. Also on the draft control block is the adjustable valve (small one) and solenoid valve connected to switch on dash. The splitter block in the lift circuit has two hoses from the lift valve (joystick), two hoses to each lift cylinder and the two hoses from the draft control block.
So here's how I think it all works, and I reserve the right to change my mind at any time. First when you switch on the draft control, the solenoid operates and opens two hyd paths. one is from the lift splitter block back to the tank. so if your not stepping on the tram the loader is , for all practical purposes, in float and theirs no lift being applied to the loader. The solenoid valve also opens a path thru the adjustable valve from the tram circuit to the splitter block, so when you step on the tram pressure is applied from the pump to the splitter in the lift circuit. I think the amount of lift applied is determined by the difference in flow allowed thru the adjustable valve and what can flow back thru the return which is probably restricted somewhat.
like I said, this theory is not official. just my trying to think it thru.

Reg

 

[ponytug]

Dear RegL,

I think that is pretty close. The draft control is actually a pressure regulator, so as you turn the knob, the pressure in the lift arms rises or falls, controlling the amount of weight transferred to the tractor. To do that, the pump (engine) has to be going fast enough to generate the required pressure, which is usually somewhat above idle.

To make that happen is hydraulically a little complicated, but there are two examples on this page, of which this image shows what I think we have;


I hope that this helps.

All the best,

Peter

 

[woodlandfarms]

So now this got me thinking..... My pt has the worst leak down. I mean it reall goes down quick with a load. I wonder if this circuit has anything to do with it.

 

[ponytug]

Carl-
The likely candidate is the the check valve on the hydraulic control. I have had to clean debris out of mine.

Looking at the above figure, if the check valve to the tank is not seating properly, it would cause leak down in the arms. It should be pretty easy to clean out. Just be careful of the aluminum block. Terry once warned me about being gentle with it so as not to strip threads.

All the best,

Peter

 

[SpringHollow]

My lift leaks down too. I believe this is typical to the valve used. I had catastrophic leak down a couple of years ago - would randomly drop. It ended up being the steering cylinders needing to be rebuilt. They are in the same circuit but have priority.

Ken

 

[J_J]

Unless you have reliefs in the work ports, it is not the valve relief that is leaking.

The valve relief does not come into play until you move the lever.

So if your lift arms are leaking down, with the lever in neutral, it is most probably the cyl seals, and maybe 10 % chance it is the valve spools.

With the lift cyl retracted, remove the base end hose from both cyl and retract some more.

If the seals are leaking, fluid will flow out the cyl base end ports. You might have to isolate which cyl by capping a hose

 

[Bob999]

A while back, on my 1430, the draft control stopped working. After some time I isolated the problem to the adjustable hydraulic valve in the draft control unit. Terry doubted that was the trouble and Keith said he couldn't remember ever sending out a replacement for one. I ordered a new one anyway, for close to $200..
The replacement is not exactly the same as the original but the draft control is working, but only when I crank the valve all the way down. I'm going to call Keith back this week to see if I can get the correct valve. Just wanted to share and wondering if anyone else has had draft control problems.

I had a similar problem. I was mowing and the draft control suddenly stopped working. (As others have posted what is called a draft control on the PT differs from draft control on a conventional tractor--on the PT the draft control transfers some (or all, depending on the setting) of the weight of the attachment to the tractor.)

I called Terry and he suggested that it was likely a small bit of foreign matter disrupting the operation of the draft control valve. It took me a couple of tries removing the control valve from the aluminum block and cleaning before it began normal operation again. I never saw any foreign matter but apparently there was some that was dislodged/removed by removing and cleaning the valve.

 

[RegL]

Bob, how did you clean the valve. I didn't throw away the old one yet.

 

[Bob999]

Bob, how did you clean the valve. I didn't throw away the old one yet.

I removed the valve cartridge and cleaned it using a clean cloth and compressed air. I also carefully examined the o ring and spacer to ensure they were in good shape.
I used suction to pull oil out of the cavity in the aluminum block on the theory that foreign matter might remain in the cavity.

As an aside, my valve cartridge is Sun brand and there are identifying numbers on the side(s) of the cartridge that allowed me to find the cartridge on the Sunhydraulics web site. That gave me a better understanding how it works.