Bobcat 763 aux Hyd problem ?

[toohp]

Hi , I have a 1999 763 thats giving me Aux Hyd problems . It wont let me open the 4 in 1 bucket but will let me close it . Ive thrown $ 1000 trying to fix this problem with the mech but no luck . I have replaced the coils several times , resealed the valves , replaced the 4 relays , installed a new switch on hand control but still no luck . It works in the morning but after say 1 -2 hrs it stops working, sometimes works after resting it for an hr or so , to me I think its an electrical heat issue re a component ??? I read the way bobcat powers up the coils is complex , can I bypass the bics & rewire it in a more simple way ? Mine has the led gauges . Cheers

 

[Tazza]

Have the stems been replaced too?
When it stops, does it stay that way for a while?
I'm wondering if you can keep it running, flip the cab up and see if the coil is still getting power when activated. This will tell you if it's electrical or mechanical

 

[toohp]

Have the stems been replaced too?
When it stops, does it stay that way for a while?
I'm wondering if you can keep it running, flip the cab up and see if the coil is still getting power when activated. This will tell you if it's electrical or mechanical

No Stems havn't been replaced . Will look into that today . Yes once the problem happens stays like that for a while , sometimes after shutting the machine down for say 1 hour it comes good but yesterday it didn't .

 

[Tazza]

No Stems havn't been replaced . Will look into that today . Yes once the problem happens stays like that for a while , sometimes after shutting the machine down for say 1 hour it comes good but yesterday it didn't .

You can actually dismantle them if you're careful. Give them a good clean and re-assemble. It may work, it may not.

 

[toohp]

You can actually dismantle them if you're careful. Give them a good clean and re-assemble. It may work, it may not.

Mech replaced the seals on stems but the dealer said I should have replaced them . One of those stems is $650 ! Is the stems & coils the only thing that controls the flow for the Aux Hyd ? or is there more inside the control valve ? My machine has 7000 hrs ive spent $5000 since xmas I need to put a budget on the repairs thinking I should just upgrade it as it needs a lot spent on bobtach pins & bushes plus axle bearing on the way out too ? Looking at a Bobcat S!85 2010 witrh 1200 hrs in it on monday , they ok ? Cheers

 

[Tazza]

Mech replaced the seals on stems but the dealer said I should have replaced them . One of those stems is $650 ! Is the stems & coils the only thing that controls the flow for the Aux Hyd ? or is there more inside the control valve ? My machine has 7000 hrs ive spent $5000 since xmas I need to put a budget on the repairs thinking I should just upgrade it as it needs a lot spent on bobtach pins & bushes plus axle bearing on the way out too ? Looking at a Bobcat S!85 2010 witrh 1200 hrs in it on monday , they ok ? Cheers

The stems aren't that expensive, surely. I paid about $100 USD each for PWM ones for an S250, yours can't be much more than that.
The way I understand that they work is they have a tiny spool inside, this allows fluid to move in either end of the main spool inside the control block, sort of like this:
---> ======= <------
The arrows being fluid from the stems and the ====== being the spool that diverts the axu oil in the control block.
If you get some aluminium to use as soft jaws on a vice, grab the part with the Orings in the soft jaws then un-screw the hex part, it should simply un-screw.
Once open, be careful to not loose anything, there are small washers and springs in there. Give it a good wash and blow out, make sure the little spool is free to move in the end that you held in the vice. Give it a good oil up and put back together.
I had an S150 that was sitting for a while before I got it. The bucket opened one way only. I opened the stem and freed the spool and it works perfectly now.

 

[mmsllc]

The stems aren't that expensive, surely. I paid about $100 USD each for PWM ones for an S250, yours can't be much more than that.
The way I understand that they work is they have a tiny spool inside, this allows fluid to move in either end of the main spool inside the control block, sort of like this:
---> ======= <------
The arrows being fluid from the stems and the ====== being the spool that diverts the axu oil in the control block.
If you get some aluminium to use as soft jaws on a vice, grab the part with the Orings in the soft jaws then un-screw the hex part, it should simply un-screw.
Once open, be careful to not loose anything, there are small washers and springs in there. Give it a good wash and blow out, make sure the little spool is free to move in the end that you held in the vice. Give it a good oil up and put back together.
I had an S150 that was sitting for a while before I got it. The bucket opened one way only. I opened the stem and freed the spool and it works perfectly now.

To easily verify the problem at hand with out throwing even more money at the problem, install two test lights that are tapped into both hydraulic auxiliary coils. Carefully run wiring into the cab to watch them while operating the machine. The next time the issue occurs, make sure the lights still come on while the auxiliary switch(s) is / are pressed. By doing that, it will help rule out an electrical / control issue versus a stuck stem. If the light stays on, then repair / replace the stems. If the lights don't stay on, then start chasing the electrical harness from the stems to the control switches. Despite the installation time / labor, it will help keep more of YOUR money in YOUR pocket.

 

[toohp]

To easily verify the problem at hand with out throwing even more money at the problem, install two test lights that are tapped into both hydraulic auxiliary coils. Carefully run wiring into the cab to watch them while operating the machine. The next time the issue occurs, make sure the lights still come on while the auxiliary switch(s) is / are pressed. By doing that, it will help rule out an electrical / control issue versus a stuck stem. If the light stays on, then repair / replace the stems. If the lights don't stay on, then start chasing the electrical harness from the stems to the control switches. Despite the installation time / labor, it will help keep more of YOUR money in YOUR pocket.

Thanks heaps guys , just 1 more question if ok ? I just tilted the cab & disconnected the wire to each coil to try & find out which coil & stem the aux hyd work off , there s 2 coils on top of valve bank & 1 going into the side of Bics . But I disconnected 1 coil at a time then ''ALL 3'' & the aux hyd still works ,( how does this work ) so.... is it the 2 ontop of valve bank that work the aux hyd or all 3 Inc the horizontal bics one ?? The only thing that wouldn't work was lift & tilt once the bics was disconnected . The issues getting worst as I got the aux hyd the stop only after several minutes of opening & closing with all wires ''connected '' unlike previously after several hours after getting hot , a good thing if I need a electrician to check . And yes unfortunatly 1 of those stems here in Oz is $650 ! Part no 6665758 stem Part no 6666616 stem $193 6667687 $ 231 Parts here are getting Crazy !!!! Several years ago I replaced the fan motor , I got it from the states for $200 on special Here in Oz they wanted $1,300 !!!!!!! Cheers Toohp

 

[Tazza]

Thanks heaps guys , just 1 more question if ok ? I just tilted the cab & disconnected the wire to each coil to try & find out which coil & stem the aux hyd work off , there s 2 coils on top of valve bank & 1 going into the side of Bics . But I disconnected 1 coil at a time then ''ALL 3'' & the aux hyd still works ,( how does this work ) so.... is it the 2 ontop of valve bank that work the aux hyd or all 3 Inc the horizontal bics one ?? The only thing that wouldn't work was lift & tilt once the bics was disconnected . The issues getting worst as I got the aux hyd the stop only after several minutes of opening & closing with all wires ''connected '' unlike previously after several hours after getting hot , a good thing if I need a electrician to check . And yes unfortunatly 1 of those stems here in Oz is $650 ! Part no 6665758 stem Part no 6666616 stem $193 6667687 $ 231 Parts here are getting Crazy !!!! Several years ago I replaced the fan motor , I got it from the states for $200 on special Here in Oz they wanted $1,300 !!!!!!! Cheers Toohp

The coils you want are the two that are vertical, not the one that is horozontal, that is to lock the lift function out.
When one coils is removed, it should only work in one direction.
You're right about prices over here, they really nails us on some things.

 

[toohp]

The coils you want are the two that are vertical, not the one that is horozontal, that is to lock the lift function out.
When one coils is removed, it should only work in one direction.
You're right about prices over here, they really nails us on some things.

So Ive thrown more $ at it and still havn't been able to fix it but we have now found out its electrical !! One problem was its a high flow so we were working on the wrong valve bank . Ok Ive got power from switch to relay then it looses pwr from relay o solinoid somewhere . We have fears the harness go's via the computer althou we cannot see that . We tried to bridge the wire from relay to solinoid & bypass the faulty wire but it caused the bucket to open and to continue to open by itself then stick in the open position , we quickly disconnected the bridge for fears of doing damage to computer or something ? Ive asked the sparky why cant we bypass the computer but he does not want to that . Going to try and track down the bad wire but can it be in the computer ? any suggestions ?

 

[Tazza]

So Ive thrown more $ at it and still havn't been able to fix it but we have now found out its electrical !! One problem was its a high flow so we were working on the wrong valve bank . Ok Ive got power from switch to relay then it looses pwr from relay o solinoid somewhere . We have fears the harness go's via the computer althou we cannot see that . We tried to bridge the wire from relay to solinoid & bypass the faulty wire but it caused the bucket to open and to continue to open by itself then stick in the open position , we quickly disconnected the bridge for fears of doing damage to computer or something ? Ive asked the sparky why cant we bypass the computer but he does not want to that . Going to try and track down the bad wire but can it be in the computer ? any suggestions ?

It's always possible the issue is in the computer, but hopefully not. If you think it could be a wire, you will need to trace it from the coils back to the controller. They are all numbered, so that makes it easier to trace.
Check all the points where the harness touches the frame between the computer and the coils.
I really hope you find the problem.... I'd hate be be the one that has to keep putting more money in and it still doesn't fix it.

 

[toohp]

It's always possible the issue is in the computer, but hopefully not. If you think it could be a wire, you will need to trace it from the coils back to the controller. They are all numbered, so that makes it easier to trace.
Check all the points where the harness touches the frame between the computer and the coils.
I really hope you find the problem.... I'd hate be be the one that has to keep putting more money in and it still doesn't fix it.

Ok , I got a electrician out again the other day to try and fix this problem . But no good looks like the problem is in either the PWm module or the smaller other diode module , problem lies with which one do I replace the pwm is $900 Inc or the smaller one is $400 Inc or do I do both $1300 ! Ouch . ?? Ive tracked down a much cheaper new PWM overseas but it will take time to get here . Which one normally acts up the most ? Suspose I could replace the cheaper one first , then wait till the cheaper PWM arrives from OS .

 

[Tazza]

Ok , I got a electrician out again the other day to try and fix this problem . But no good looks like the problem is in either the PWm module or the smaller other diode module , problem lies with which one do I replace the pwm is $900 Inc or the smaller one is $400 Inc or do I do both $1300 ! Ouch . ?? Ive tracked down a much cheaper new PWM overseas but it will take time to get here . Which one normally acts up the most ? Suspose I could replace the cheaper one first , then wait till the cheaper PWM arrives from OS .

I'd like to suspect the smaller module, but without one to plug in to test, it's really just a guessing game.
I have never had one go bad on me, so i can't say what the most common one is to go bad.
Is your machine a G series? the module you are talking about, is it the small box that the BICS box connects to? can you get a picture and look up my profile and send it to me?

 

[toohp]

I'd like to suspect the smaller module, but without one to plug in to test, it's really just a guessing game.
I have never had one go bad on me, so i can't say what the most common one is to go bad.
Is your machine a G series? the module you are talking about, is it the small box that the BICS box connects to? can you get a picture and look up my profile and send it to me?

Update . Problem solved - Faulty Diode Module part no 6664 388

 

[7LBSSMALLIE]

Update . Problem solved - Faulty Diode Module part no 6664 388

thanks for the case closed post that means alot to us. glad we could help.