Bob-Tach Not Responding

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owensge

Well-known member
Joined
Oct 17, 2003
Messages
326
Hey all, my bob-tach stopped working yesterday and is not responding when I press the switch in either direction. I don't hear a groan from the hydraulics at all (the hydraulics are working fine everywhere else) when I press the switch.
I'm getting power to the switch and when I press it there is a drop in voltage. I've checked fuses and connections and those look fine.
Could it be a simple as replacing the switch (could it be bad) or is there somewhere else I need to look.
Any ideas on the best way to troubleshoot this?
Thanks
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
I would imagine that you have check the obvious, grease the wedges, looked for bent or binding parts. Does the cylinder try to extend or retract? (see play in the pins move from side to side) Sounds like its trying to move the cylinder but can't. If you hold the switch and try the handles manualy, maybe you can help it enough to get it open.
Ken
 

owensge

Well-known member
Joined
Oct 17, 2003
Messages
326
I would imagine that you have check the obvious, grease the wedges, looked for bent or binding parts. Does the cylinder try to extend or retract? (see play in the pins move from side to side) Sounds like its trying to move the cylinder but can't. If you hold the switch and try the handles manualy, maybe you can help it enough to get it open.
Ken
I haven't tried to grease the wedges. The cylinder does not budge and there is no play in the pins.
I think I'll grease the wedges tomorrow and hold the switch to see if I can do it manually.
I've been running my brush mower attachment on it for a couple of days on some really steep grades. Now that I look at it, the attachment seems to fit a little snug like it gained some weight on me.
I'll give your suggestion a try and let you know if it works.

Thanks Ken
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
I haven't tried to grease the wedges. The cylinder does not budge and there is no play in the pins.
I think I'll grease the wedges tomorrow and hold the switch to see if I can do it manually.
I've been running my brush mower attachment on it for a couple of days on some really steep grades. Now that I look at it, the attachment seems to fit a little snug like it gained some weight on me.
I'll give your suggestion a try and let you know if it works.

Thanks Ken
Owensge
Sorry i miss read your first post, guess is was late last nite...
See this morning you say it does Not groan. I'm asumeming you heard some sort of Hyd noise when you operated the power bobtach switch normally. I personally don't have one of these. However if its like most of Bobcats elec/hyd controls, this is going to be a coil (cylindical shape, color of grade 8 bold , with 2 red wires coming from it) that slides over a spool, with a nut on top of it (in the center) holding the coil down. There is likely one for each direction of the cylinder. These coils are also used to control your front quick couplers, bucket leveling so finding the corect “pair” may take some investigation.
If you take the nut off the top, then the coil can slide off the spool in the center, when the coil is powered up, the magnetic field it creates will try to hold it on the on the spool, and you can verify that it is functioning.
A more common symptom would be either, 1; no voltage drop, hence no responce either direction, 2;voltage drop one way (with responce) and none the other dirrection.
It sounds like your coils are drawing power, I guess first, I'd try to check if its getting to the coils. One wire should be ground and the other hot when the switch is pressed.
As for the nut that hold the coil on, Tighten it VERY gently. (use a little blue loctight and tighten just past finger tight ) Also be very gental with the spool inside the coil. Dropping, banging or rough handling of any sort not permmited. There is a needle inside the spool that the magnetic field of the coil moves to open and close the valve. Any distortion of the spool can bind the needle and ruin the spool. ($90 each), dirt inside the system can have same binding effect.
They way both sides stopped responding it sounds like an power supply issue, if it was hydraulic, then it should be one side or the other. So I may be barking up the wrong tree, but I'd start with checking that the coils have power.
Regards
Ken
 

owensge

Well-known member
Joined
Oct 17, 2003
Messages
326
Owensge
Sorry i miss read your first post, guess is was late last nite...
See this morning you say it does Not groan. I'm asumeming you heard some sort of Hyd noise when you operated the power bobtach switch normally. I personally don't have one of these. However if its like most of Bobcats elec/hyd controls, this is going to be a coil (cylindical shape, color of grade 8 bold , with 2 red wires coming from it) that slides over a spool, with a nut on top of it (in the center) holding the coil down. There is likely one for each direction of the cylinder. These coils are also used to control your front quick couplers, bucket leveling so finding the corect “pair” may take some investigation.
If you take the nut off the top, then the coil can slide off the spool in the center, when the coil is powered up, the magnetic field it creates will try to hold it on the on the spool, and you can verify that it is functioning.
A more common symptom would be either, 1; no voltage drop, hence no responce either direction, 2;voltage drop one way (with responce) and none the other dirrection.
It sounds like your coils are drawing power, I guess first, I'd try to check if its getting to the coils. One wire should be ground and the other hot when the switch is pressed.
As for the nut that hold the coil on, Tighten it VERY gently. (use a little blue loctight and tighten just past finger tight ) Also be very gental with the spool inside the coil. Dropping, banging or rough handling of any sort not permmited. There is a needle inside the spool that the magnetic field of the coil moves to open and close the valve. Any distortion of the spool can bind the needle and ruin the spool. ($90 each), dirt inside the system can have same binding effect.
They way both sides stopped responding it sounds like an power supply issue, if it was hydraulic, then it should be one side or the other. So I may be barking up the wrong tree, but I'd start with checking that the coils have power.
Regards
Ken
Ken, I took a look at the coils and they were off the stem just dangling there. The nut must have come off.
0530062318a.jpg

I haven't pulled the coils out yet to see if they have been bored out by the vibration, but I went ahead and bought two new ones anyway (I ordered a new stem as well).
Any suggestions/tips on removing and replacing the stem?
Thanks for your help..
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
Ken, I took a look at the coils and they were off the stem just dangling there. The nut must have come off.

I haven't pulled the coils out yet to see if they have been bored out by the vibration, but I went ahead and bought two new ones anyway (I ordered a new stem as well).
Any suggestions/tips on removing and replacing the stem?
Thanks for your help..
The nuts can't be torqued to hold things together, hence the blue loctite.
Hmmm... I was expecting 2 separate coils, but these are combined I see.
The coils just slip loosely over the stems, say .030 to .050 clearance. You don't even need the nut to hold them on (you could use black tape or something), you can test their function just buy slipping the on. Hold the switch and see if there is a magnetic field pulling them onto the stems. If they function, I believe I'd leave the existing stem in and return, or pehaps keep the new one for a spare, especially if it is the same part # as the stems for the front quick couplers
If you decide to change the stem, just don't bang the stem or drop it and don't try to torque the nut more then barely snug. Aside from that just normal precautions, clean dirt away, use correct wrench on base of stem, new stem should come with new o rings on it.
If one of these electric functions act up you can test the coil as described above, or if you think the problems is in the stem they can be switched side to side to see if the problem is electrical or the stem.
However I can't say I have been formally trained in this, its just some trouble shooting I pick up along the way, (and based on the 3rd valve coils on my 773) I hope it helps
Ken
 

owensge

Well-known member
Joined
Oct 17, 2003
Messages
326
The nuts can't be torqued to hold things together, hence the blue loctite.
Hmmm... I was expecting 2 separate coils, but these are combined I see.
The coils just slip loosely over the stems, say .030 to .050 clearance. You don't even need the nut to hold them on (you could use black tape or something), you can test their function just buy slipping the on. Hold the switch and see if there is a magnetic field pulling them onto the stems. If they function, I believe I'd leave the existing stem in and return, or pehaps keep the new one for a spare, especially if it is the same part # as the stems for the front quick couplers
If you decide to change the stem, just don't bang the stem or drop it and don't try to torque the nut more then barely snug. Aside from that just normal precautions, clean dirt away, use correct wrench on base of stem, new stem should come with new o rings on it.
If one of these electric functions act up you can test the coil as described above, or if you think the problems is in the stem they can be switched side to side to see if the problem is electrical or the stem.
However I can't say I have been formally trained in this, its just some trouble shooting I pick up along the way, (and based on the 3rd valve coils on my 773) I hope it helps
Ken
Ken, things are working fine now after I cleaned everything up and put in a new nut and spacer.
Thanks for the tips!
 
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