bobcat 7753 Aux hyd

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tackletree

Member
Joined
Feb 6, 2009
Messages
17
I am having problems with my aux hyd in my 7753 melroe bobcat. I need some help troubleshooting. All other hyd functions work fine. problem is that my aux hyd work but not consistantly. I am running a grapple bucket with it. Sometimes it works right away like it should but then there is a delay. It will close the grapples then it will stop before closed all the way. I can hear the hissing sound when the aux start to activate so I think it isn't the grapple bucket. At a loss. Pulled the spool to aux, springs look good seleniods are magnetizing but at a costant ( was told that maybe they should pulse). Any help would greatly be appreciated thanks
 

thetool

Well-known member
Joined
Mar 22, 2008
Messages
516
If you have pwm aux, or variable-flow aux they will pulse but so fast you won't be able to tell the difference.
If it hestiates in one direction only, try switching the coils (solenoids) around and see if the hesitation changes direction. If it does not change, try then switching the stems.
If it hesitates in both directions, BOTH coils and/or stems could be on the fritz, but not likely.
Things common then to act-ups in both directions are the switch on the handle, the valve spool sticking, the controller, and of course the wiring harness.
The outputs from your handle switch in neutral will be about 4 volts, or range with movement from very low or zero up to 8V or so. This is a potentiometer for controller input.
The controller is usually condemned by eliminating everything else. Oh yeah-the button pad can get you, too, but I don't know how to troubleshoot that thing, except for a feeling I get when I see the way lights flash on it.......=).
If you don't have variable flow, you still have the coils and stems but they are 12v on/off and simpler to troublshoot. Rather than a controller, you have relays, under the cab, a cluster of four, if I remember correctly. If they are getting worn, they can cause such problems, too.
Some stuff to look for, good luck
Shane
 
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tackletree

Member
Joined
Feb 6, 2009
Messages
17
If you have pwm aux, or variable-flow aux they will pulse but so fast you won't be able to tell the difference.
If it hestiates in one direction only, try switching the coils (solenoids) around and see if the hesitation changes direction. If it does not change, try then switching the stems.
If it hesitates in both directions, BOTH coils and/or stems could be on the fritz, but not likely.
Things common then to act-ups in both directions are the switch on the handle, the valve spool sticking, the controller, and of course the wiring harness.
The outputs from your handle switch in neutral will be about 4 volts, or range with movement from very low or zero up to 8V or so. This is a potentiometer for controller input.
The controller is usually condemned by eliminating everything else. Oh yeah-the button pad can get you, too, but I don't know how to troubleshoot that thing, except for a feeling I get when I see the way lights flash on it.......=).
If you don't have variable flow, you still have the coils and stems but they are 12v on/off and simpler to troublshoot. Rather than a controller, you have relays, under the cab, a cluster of four, if I remember correctly. If they are getting worn, they can cause such problems, too.
Some stuff to look for, good luck
Shane
I think they are just the 12v. What do I need to look for in the relays? I still feel like it is something in the cotrol valve. Checked power from the thumb switch to seleniods. All good. Just dont know enough about the "Guts" of the control valve. It seems like it is bypassing. Hit the tswitch "either way" then there is a delay, hear the hissing sound then grapples activate, sometimes all the way and sometimes not. when it does this i can move the sticks or foot peddles and it helps it to begin working again. But sometimes it works as if there is nothing wrong.
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
I think they are just the 12v. What do I need to look for in the relays? I still feel like it is something in the cotrol valve. Checked power from the thumb switch to seleniods. All good. Just dont know enough about the "Guts" of the control valve. It seems like it is bypassing. Hit the tswitch "either way" then there is a delay, hear the hissing sound then grapples activate, sometimes all the way and sometimes not. when it does this i can move the sticks or foot peddles and it helps it to begin working again. But sometimes it works as if there is nothing wrong.
On the Aux mode button up on the dash, it has 2 green lights, one light on makes the aux work for intermittent use like a grapple, 2 green lights on for continuous flow like a hoe or brusher. Anyway, these two lights never go into a alternating flash? If not then your wiring and electrical should be fine.
Swap the coils, then the stems as mentioned
Ken
 
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tackletree

Member
Joined
Feb 6, 2009
Messages
17
On the Aux mode button up on the dash, it has 2 green lights, one light on makes the aux work for intermittent use like a grapple, 2 green lights on for continuous flow like a hoe or brusher. Anyway, these two lights never go into a alternating flash? If not then your wiring and electrical should be fine.
Swap the coils, then the stems as mentioned
Ken
No flashing lights. I will try swapping the selenoids. Not sure if I can swap the stems. Any Idea how to do this. there is a nut on the top of the seleniods to remove but did not see any way to remove the stems. Thanks
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
No flashing lights. I will try swapping the selenoids. Not sure if I can swap the stems. Any Idea how to do this. there is a nut on the top of the seleniods to remove but did not see any way to remove the stems. Thanks
1st off, Don't torque the nut that holds the coil on the stems, you will ruin the stem. (if they flex the control needle inside wil jamb) Finger tight only with blue loctight would be good.
Pull the coil off and below the coil will be a a place to put a wrench on the stem. Unthread it and swap it with the other stem.
If you have problems going on direction (say close the grapple) it could be a stem, but if you problems are in both open and close, then you either have 2 bad stems (not likely) or some other problem.
Ken
 
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tackletree

Member
Joined
Feb 6, 2009
Messages
17
1st off, Don't torque the nut that holds the coil on the stems, you will ruin the stem. (if they flex the control needle inside wil jamb) Finger tight only with blue loctight would be good.
Pull the coil off and below the coil will be a a place to put a wrench on the stem. Unthread it and swap it with the other stem.
If you have problems going on direction (say close the grapple) it could be a stem, but if you problems are in both open and close, then you either have 2 bad stems (not likely) or some other problem.
Ken
Hopped in the machine today and aux worked like it should. Didnt put too many hours on it but it is working better than ever before. Not sure what the deal is but hope it was something simple that just worked itself out. I will for sure let yall know if it begins to act up. never did anything with the coils or stems. thanks for the replies
 

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