Just finished putting new chain oil in the chain case and re-bushing the drive assembly and everything was fine until after running for about an hour. could be I dislodged or knocked something in the wiring OR a new problem? Problem is the thumb switch for opening the bucket works fine but the closing switch just stopped working. Then it worked a bit with fiddling the switch then it stopped again. Now at the same time the close bucket switch stopped working when I checked the other switches the stabiliser stands on the rear also stopped working and along with that came the fact that when I operate the stand switch it actually closes the bucket slowly?????????? So I am part way through filling a new septic trench so I will make the best of it but is someone can assist in giving me direction knowing that I know very little that would be a great help. Are you reading ATCO - I am sure you would have a good idea - the other thing that I think may have changed but cant be sure is there appears to be a loud tappet type noise (but not tappets) coming from over my left shoulder that was not there before - is there some sort of valve assembly that could have frozen??? Guidance as to where it is or a photo??? Thanks for anyone who can help, Regards, MX45
Switch for opening/closing bucket? Are you talking about that thumb switch on right drive lever knob that operates the auxiliary circuit, like a grapple bucket attached to the machine? I haven't worked on a unit that has the rear stabilizers. The switch that operates them, would that be one of the rocker switches on the drive lever knob? Not sure what the tapping noise would be. If it's doing it constant, should be able to narrow down the area it's coming from.
G'day Willie, Yes the thumb switch on the right lever. The switch that operates the stabilisers (lift hydraulics for using backhoe) is the same switch but on left hand lever. Intermittent fault - rear stabilisers worked and the bucket switch did not but the bucket still closed very slowly and with little real pressure when stabilisers worked and when they did not. Could not associate the fault with anything in particular except I was inside it doing that chain case and the drive levers - could have sat on something or stood on something that connects underneath. When the bucket does not operate it is a complete failure - as when it does operate you can see the hydraulic hose jump with the pressure supply. So my thinking is electrical but dont know how that would effect the stabilisers unless the supply is from the same source - but then why does the bucket close - some sort of pressure relief valve flowing into that circuit???? Sorry dont know a thing so just making any thoughts. Bobcat worked fine today with no issues and finished the septic infill -thank God for that smell being buried! Regards.
Well, I'm a little vague in memory of exactly how the switches on drive lever knobs were configured on the 753, got too much misc junk inside my head. If it's like the later model controls, the switch on left knob is a rocker switch that toggles from center position, the switch rocks up and down. There is a similar switch on the right knob, probably the one you are saying operates the backhoe stabilizers, same type of rocker switch. I assume those are the switches that you are saying is giving you trouble. There is also a side to side operating proportional switch on right knob on later models that operates the main aux pipes on side of boom, you're not having problems with this switch or circuit? The 753, does it have a seat switch that requires your arse to be sitting in seat to get things to operate? I only ask this as to know if seat switch is on machine and would affect testing switches. Those rocker switches on Bobcat control knobs do go bad, I've replaced a good number of control knobs. Problem is, Bobcat made those switches a sealed unit inside the control knob, you have to replace the drive lever control knob as a unit.
Willie, the problem I had with the Bobcat 753, fixed itself (yea I know, things dont fix there self) the bucket tilts like it should. I still have the alarm buzzer, I have always had. The upper RH panel has never worked since I bought it (18 days ago) Now the old problem started again, engine starts and shuts off. the fuel solenoid, goes to shutoff. I guess there is something telling it to shut down. I checked the oil press switch, I looked for a temp shutoff sending unit, but I didnt see one, I found the temp sending unit (I think) on the radiator. the relay just before the fuel shutoff solenoid is clinking. You can turn the key on, fuel shutoff goes to run and in about 5 seconds it goes to shutoff I needed it bad and I disconnected the shutdown and tied it in run position. I know I was taking a chance, but this is my second used Bobcat in two months, so Im a chance taker LOL This problem exists the very first time I try to start in in the am, so its not running hot, hyd fluid is full, everything looks normal. Machine runs and operates like it should, with the shutoff tied back. Im wondering if the relay is bad?? Serail number 508611942
753, that's getting back in my memory of how they were set up. If I remember correctly, they used the 3 wire pull solenoid to put engine in run position. Red wire=hold, black wire=ground, white wire=pull. The white wire can only have power for appx 5 seconds max, any longer it will smoke the solenoid. If the 753 is similar to the later versions, the ground on black and voltage feed on red is controlled by ECU. When you turn on ignition, the ECU also powers up a fuel relay which sends voltage to white wire, then ECU takes power away from that relay after a few seconds. I hope this may give you some info to work with.
G'day Willie, the control switches are rocker switches (return to centre) and rock from left to right not up and down. There is no other proportional switch as far as I know. The right hand switch(bucket) feels looser than the left - I guess more use and wear? They both return to a central position.(There is a trigger switch on the front of each drive lever that does not appear to do anything when pressed in???? I pulled the rubber boot down from the switch assembly and there appears to be two plastic tabs in the handle assembly which either lift or there is a screw or something under perhaps??? Do you know??? To remove them that is if necessary. The seat appears to have a switch under for the machine to operate - I can hear it click when I press and release with my hand. The kitty cat did allow the bucket to work for a couple of hours the next day without fault - so intermittent gremlin might be a bit hard to chase but would be good to know where to chase it if it happens again. Looked at the recent work and no oil sweat from the new siliconed chain case yet and so hopefully no water ingress. Bobcat has worked about four to five hours since sealing so looks good. Just had it steer a little left going forward and a little right going backwards so I have adjusted the LHS lever a little more forward - will see how that goes soon. Regards, MX45
Well, it's been so long since I've worked on a 753, I can't really remember how the switch controls are set up, don't know if I can advise much on troubleshooting those circuits. On the later models, the trigger on right control knob would lock in aux position, like when you're operating a backhoe, might be different on the 753. To completely remove the control knob from the drive lever requires removing the plug connector at end of harness, where harness comes out of drive lever tube. Then you unlock the knob where it's connected to the drive lever tubes by lifting those locking tabs that you referred to and pull the control knob off of the drive lever tube, pulling wire harness out along with it.
For keeping the aucilliary flow continuous for backhoe you press the aux button the upper right hand dash twice and a second green light comes on indicating continuous flow. so different set up. Thanks for the info on detaching the control knob if need be - did you mean that has to be replaced as an assembly or can the knob be dismantled for replacing just the switch? Since it was both flick switches at the same time I am wondering if they have a relay or valve in common or sequence that could cause this failure? Where would I find those common valves if you might have an idea? I will have a fiddle with those trigger switches just to see if after all this time it is just something I dont understand about how it functions. Thanks Again - Nice to smell clean air on this end.
I had a faint memory in my head that the 753 had that button on the right side that had the two LED's that light up for momentary or continuous aux operation but wasn't sure. I really can't remember much about those machines, can't offer much info on controls or valves, but it would not surprise me if it's happened to be just faulty switches, seen it plenty of times on various models. On the ones I've worked on, Bobcat made those switches a sealed unit inside the control knob, have to replace the entire knob when you have a faulty switch. Bobcat machines originally had an operators handbook attached to a cable in a pouch behind the seat that would tell what the switch functions are, is your handbook missing?
Thanks Willie - the book is there but I think the machine is a little different. I had a look under the seat just in case I moved something and checked all the electrical connections,etc., Could be I got a little water in one of them when cleaning all the garbage from the inside of the machine. Did not find anything though. I will let you have a rest for now and I will update you when it plays up again as to what transpires. I have got the bottom of the trench pretty level as it flooded with the suppressed flow from the old trench line when I broke into it. One of those feelings of oh ... hope that is what I think it is - as I hit it a bit earlier than I had anticipated. River gravel is from my property - bit of a hike more than 100 meters away and about 10 ton I expect of gravel in 20 meter trench. Thanks again - no more questions for now, Regards, MX45
No worries MX45, anytime you have a question just throw it out here. BTW, nice work.
I have a bobcat s220 and the bucket tilt falls on its on and it does it on or off. both tilt cylinders are rebilt and still have same problem.. I have did everything possible looking for a leak and cant find one.. i dont have a schematic or service manual.. so im looking for some input on what to check next. thanks for any help