Proportional control not so proportional

[Tazza]

Anyone had a machine with proportional controls that only work at full power? and not quite as responsive as i believe they should be.
I have a 753G with proportional aux hydraulics but only works at full power. New stems were installed but they work the same. Can put the coils on a screwdriver and you can feel the buzzing alter as you move the thumb switch further across.
The only thing i can sort of think of is the aux. spool isn't moving as freely as it should in the control block. I haven't opened up the control block yet, i was going to leave that as a last resort.
Is this a known issue for the new fangled PWM controlled aux hydraulics that have been sitting for a while?
The machine was used in a coal mine, i don't believe the aux hydraulics were ever used. It had a smooth bucket installed and the wedges were welded down. The quick couplers were rusted shut. I don't think it ever saw an attachment other than the bucket.
It has done a little over 1,000 hours.
My S150 had a sticky stem from lack of uses (only a few months before i bought it), i pulled it apart and it works great, excellent control with the thumb switch that i feel the 753G should have too.
Any ideas fellas?

 

[Bobcatdan]

The aux has two modes, variable and max. I have never played around to see what the real difference is. Honestly if I was faced with this, I would swap controllers. I see if there are any TSBs for this, but I have never seen it.

 

[Tazza]

The aux has two modes, variable and max. I have never played around to see what the real difference is. Honestly if I was faced with this, I would swap controllers. I see if there are any TSBs for this, but I have never seen it.

Thanks Dan. It's as if even though it's in vairable mode it just runs at max, but if you listen to the stem when the engine is off, you can hear the tine change, so it is in the right mode.
Sadly i have no other controller to test it with.....
It may just live how it is yet.

 

[tays87]

Thanks Dan. It's as if even though it's in vairable mode it just runs at max, but if you listen to the stem when the engine is off, you can hear the tine change, so it is in the right mode.
Sadly i have no other controller to test it with.....
It may just live how it is yet.

I had a 2001 753G which always had a 4in1 bucket on it from new, I always ran the bucket in variable mode and the proportional did work but was extremely sensative and took a bit of concentration to use where as the 185K that I know have the proportional is more usable. Jarrod

 

[Tazza]

I had a 2001 753G which always had a 4in1 bucket on it from new, I always ran the bucket in variable mode and the proportional did work but was extremely sensative and took a bit of concentration to use where as the 185K that I know have the proportional is more usable. Jarrod

Thanks for the insight Jarrod
Looks like they have done some work on it since the 753G was made. My S150 has great control, i can close the bucket fast and slow it right at the end without an issue. The 753G just slams open or shut with a delay in both directions. May turn out to be one of those things you just deal with.

 

[tays87]

Thanks for the insight Jarrod
Looks like they have done some work on it since the 753G was made. My S150 has great control, i can close the bucket fast and slow it right at the end without an issue. The 753G just slams open or shut with a delay in both directions. May turn out to be one of those things you just deal with.

That is how I find the 185K plenty of control of the speed. Coming back to the 753 I never had a delay in mine, so could the handle switch no be sending the correct signals/voltage to the coils to operate the valve proportionaly?? Just a thought Jarrod

 

[Tazza]

That is how I find the 185K plenty of control of the speed. Coming back to the 753 I never had a delay in mine, so could the handle switch no be sending the correct signals/voltage to the coils to operate the valve proportionaly?? Just a thought Jarrod

It is possible, but from what i can remember, the stems start buzzing as soon as i move the thumb switch. It could be the controller not sending it correctly to the coils though... The wiring to the handles was messed with by the previous owner, they were crimped together. Made things more interesting when i needed to remove the hand grips and re-install them. Something could be wrong there.
The delay is only say half a second, as you said, yours never had a delay so i may need to keep poking around.

 

[Bobcatdan]

It is possible, but from what i can remember, the stems start buzzing as soon as i move the thumb switch. It could be the controller not sending it correctly to the coils though... The wiring to the handles was messed with by the previous owner, they were crimped together. Made things more interesting when i needed to remove the hand grips and re-install them. Something could be wrong there.
The delay is only say half a second, as you said, yours never had a delay so i may need to keep poking around.

Maybe a software update can help. Bobcat is always tweaking stuff with the software and I easily could see improve aux control something they would play with. If a service laptop has not touched the machine in a couple years, it would be way behind. There are updates sometimes weekly. v80.1 is the most current I know off.

 

[Tazza]

Maybe a software update can help. Bobcat is always tweaking stuff with the software and I easily could see improve aux control something they would play with. If a service laptop has not touched the machine in a couple years, it would be way behind. There are updates sometimes weekly. v80.1 is the most current I know off.

That is a very good point, i highly doubt it has been pluged in since new.....

 

[skidsteer.ca]

That is a very good point, i highly doubt it has been pluged in since new.....

I had a lot of trouble with my 773g in this regard, but the controls also like to stick "flow on".
Turned out it had a broken centering spring on the spool for the aux. There are 2 caps on the valve at the ends of this spool. Held on with 2 allen (I believe ) screws, sealed with a oring. it is easy to remove the cap and springs. Then you can push the spool back and forth by hand to be sure it is nice and free.
Mine had broken bits of spring jambing it up, and when it did work, the spring to center the spool was weak and ineffective so the flow stuck on. Might be worth a check as its a 20 min job. I spent a fortune on stems before I did this.
Ken

 

[Tazza]

I had a lot of trouble with my 773g in this regard, but the controls also like to stick "flow on".
Turned out it had a broken centering spring on the spool for the aux. There are 2 caps on the valve at the ends of this spool. Held on with 2 allen (I believe ) screws, sealed with a oring. it is easy to remove the cap and springs. Then you can push the spool back and forth by hand to be sure it is nice and free.
Mine had broken bits of spring jambing it up, and when it did work, the spring to center the spool was weak and ineffective so the flow stuck on. Might be worth a check as its a 20 min job. I spent a fortune on stems before I did this.
Ken

Thanks Ken i'll have a look at that too when time allows Then i can feel happy that i have done my best to try and resolve it. I can then say i have looked at all the goodies in a control block. Never cracked that part of one open before.