1999 Bobcat 753 auxiliary stopped working

[dynapl]

Hi,

I've been a Bobcat owner for quite some time without any issues until now. I'm currently experiencing difficulties with the auxiliary hydraulics, which had been working fine the last time I used them a couple of years ago. I just bought a snowplow and rototiller and nothing is happening.

I've searched this forum for answers but to no avail. Checked all fuses. My safety seat, bar, power traction etc. lights are on, the auxiliary light turns on. I can drive the Bobcat, and the lifting and tilting functions are working as expected. It seems there is pressure in the lines, as attaching the high-pressure hose to the coupler is challenging. I've attached pictures of my current situation for reference.

I'm unsure of the next steps to take. I haven't checked the solenoid valves directly yet (from my research, they should be located under the seat on the right-hand side). Can these valves be operated directly with 12V? Any guidance or advice would be greatly appreciated.

 

[laurencen]

all V plows I have seen and used require a signal thro the 7 pin I believe to divert the flow so either side can move, same my snowblower requires the hookup to rotate the discharge chute does this V plow have any sort of connector as well as the hydraulics?

what brand of plow is it?

 

[dynapl]

all V plows I have seen and used require a signal thro the 7 pin I believe to divert the flow so either side can move, same my snowblower requires the hookup to rotate the discharge chute does this V plow have any sort of connector as well as the hydraulics?

what brand of plow is it?

The plow is FCC by Paladin 120 series mnf. in 2018. The plow doesn't have any electrical connections besides the hydraulic hoses. I've also tried rototiller which doesn't have anything but hydraulics to rotate the blades and it also did not work. It seems that my issue is bobcat related. It's just with all good fuses and all indicator lights ON, I'm not sure what to check next.

When pressing the auxiliary button should I be hearing any hyd. engagement sounds like solenoid strike etc.?

 

[reaperman]

You could unhook one of the hydro lines from either attachment and turn on the aux just to see if the machine is pumping out fluid. Naturally you would put the open end in a bucket to catch the fluid if it's coming out.

 

[richmond802]

It may the switch. I am having the same issue with my 2000 753G with a grapple bucket I just purchased. You have to replace the whole handle on the right side there are not separate parts available

 

[Hulsey shit showX7]

It may the switch. I am having the same issue with my 2000 753G with a grapple bucket I just purchased. You have to replace the whole handle on the right side there are not separate parts available

Has there been any resolution to this issue.

 

[dynapl]

I know it's been over a year, but I wanted to provide an update for anyone experiencing a similar issue. I troubleshooted the handle switch, both the rocker and trigger, using MM to check for continuity. Both were good. Next, I removed the PWM module to inspect the wiring, and nothing stood out visually. I then traced the wires to the solenoids and disconnected both. With the Bobcat running and the auxiliary hydraulics in the ON position, I checked the DC voltage at each solenoid by pressing the rocker switch. The voltage went from 0 to 0.5V DC, which was far too low but indicated some activity. This pointed to the PWM module as the likely culprit.

The original module in my unit was a 6669529 REV C HECO 4097. I couldn't find an exact match, but the Bobcat website, based on my Bobcat's serial number, recommended a replacement: the Aux Control Module for Loaders, part number 6671669, described as "for loaders without the factory-installed front auxiliary hydraulics option." This was odd since my Bobcat appears to have factory-installed auxiliaries. Regardless, I purchased the module for $584, installed it today, and voila IT'S WORKING!

 

[WVRoger]

The control module is a common issue for that vintage of bobcat. My 751 bobcat module failed two years ago and I merely bypassed it b cause there were so many different symptoms and failures causing the machine not to operate. I think this can be directly related to leaving the machine outdoors without being covered. Over time the electronics become worm and brittle. I continue to use my 751 with no module, no breaks and stilll have working front end hydraulics. You did a great job of troubleshooting this issue!

 

[reaperman]

The control module is a common issue for that vintage of bobcat. My 751 bobcat module failed two years ago and I merely bypassed it b cause there were so many different symptoms and failures causing the machine not to operate. I think this can be directly related to leaving the machine outdoors without being covered. Over time the electronics become worm and brittle. I continue to use my 751 with no module, no breaks and stilll have working front end hydraulics. You did a great job of troubleshooting this issue!

Im curious how you bypassed the module?

 

[WVRoger]

Im curious how you bypassed the module?

I ran a hot wire directly to the solenoid and use it as not only a bypass but as a kill switch to protect the machine from theft. My module has only one light lit on it at the bottom! My first failure was the break Solenoid, and I removed the metal bar initiated by the solenoid. I also had severe leakage at the control valve and was able to rebuild it in place. If you can’t work on these older machines you can’t afford to own one! My concern is safety of the machine so I am the only one to operate it and do so in WV where the terrain is hillly!

 

[WVRoger]

Im curious how you bypassed the module?

I ran a hot wire directly to the solenoid and use it as not only a bypass but as a kill switch to protect the machine from theft. My module has only one light lit on it at the bottom! My first failure was the break Solenoid, and I removed the metal bar initiated by the solenoid. I also had severe leakage at the control valve and was able to rebuild it in place. If you can’t work on these older machines you can’t afford to own one! My concern is safety of the machine so I am the only one to operate it and do so in WV where the terrain is hillly!

 

[WVRoger]

I continue to have an issue with my 751 Bobcat that has me baffled. The boom goes up but not down using the foot pedal, the boom tilts down but not up using the foot pedal. I have traced wires, checked
And verified the operation of the three hydraulics valve solenoids, checked fuses and have been asking for help at every resource I can find. No one seems to have had this issue or not exactly in this way so it’s a hard fix. Any ideas or comments are appreciated
Because this is a tough one! Is there something inside the valve bypassing or sticking? Is there a blockage in the system? Both pedals is the down motion and both horizontal actuator stems are not producing the wanted result. Thanks for your comments!

 

[brdgbldr]

I continue to have an issue with my 751 Bobcat that has me baffled. The boom goes up but not down using the foot pedal, the boom tilts down but not up using the foot pedal. I have traced wires, checked
And verified the operation of the three hydraulics valve solenoids, checked fuses and have been asking for help at every resource I can find. No one seems to have had this issue or not exactly in this way so it’s a hard fix. Any ideas or comments are appreciated
Because this is a tough one! Is there something inside the valve bypassing or sticking? Is there a blockage in the system? Both pedals is the down motion and both horizontal actuator stems are not producing the wanted result. Thanks for your comments!

Have you checked the pedal linkages for loose or broken connections?
Also, make sure that there is nothing blocking the pedals from full movement. I’ve seen machines with debris under the pedals that no one thought to was a problem until it was.

 

[spitzair]

Sounds like your auxilliary hydraulics are stuck on. I know you said you tested your solenoids but more than likely your spool valve is stuck somehow. Easy way to tell is to get a short length of 1/2" hydraulic hose, say something 3 or 4 feet long, put a male quick coupler on one end and a female on the other, then plug the hose into your aux quick couplers on the machine, thereby looping it back on itself. Start the machine and see if the problem went away. If it did then your aux hydraulics are stuck on for some reason that we'll try and figure out then.

 

[WVRoger]

Have you checked the pedal linkages for loose or broken connections?
Also, make sure that there is nothing blocking the pedals from full movement. I’ve seen machines with debris under the pedals that no one thought to was a problem until it was.

Yes, linkages are good and pedals are clear! All the solenoids are actively working and the tilt forward and boom up work fine. Tilt up and boom down do nothing. I do however have a pretty large leak on the left boom cylinder hose that will be fixed and we will try again. I suspect an issue on the valve, perhaps bypassing or gummed up

 

[WVRoger]

Sounds like your auxilliary hydraulics are stuck on. I know you said you tested your solenoids but more than likely your spool valve is stuck somehow. Easy way to tell is to get a short length of 1/2" hydraulic hose, say something 3 or 4 feet long, put a male quick coupler on one end and a female on the other, then plug the hose into your aux quick couplers on the machine, thereby looping it back on itself. Start the machine and see if the problem went away. If it did then your aux hydraulics are stuck on for some reason that we'll try and figure out then.

I suspected that could be a problem but was not sure how to unstick that valve. I thought about trying to rotate it back and forth hoping it would loosen to allow flow. Any thoughts or suggestion will be acted upon. This is going on six month issue!