S175 Auxiliary Hydraulics Problems

[chabel]

I have a 2008 S175 BICS combo valve without ACS. When I hit the aux button (either variable or max flow) on top left of cab with an attachment on like an auger, the auger starts to turn even though I have not pushed the thumb paddle switch on the right joystick. If I push the thumb paddle switch slightly to the left of center the auger stops spinning and if I push it further left it will spin the opposite direction. I thought one of the solenoids and valves on the aux spool may have gone bad so I replaced all of them. That didn't fix it. Someone at the local Bobcat shop said it is probably a bad or broken spring on one end of the aux spool that was keeping it from centering. That made sense so I replaced both ends springs and spacers on the aux spool and inspected the spool and didn't see anything obvious. That didn't fix it. Then I thought problem was with the thumb switch on the right joystick head so I bought a new one and replaced that (the old one was in bad shape anyway). That didn't do it. After studying the wiring diagrams and hydraulics schematics I'm now thinking this must be an electrical issue maybe something to do with the Pulse Width Modulation (PWM) which I think is how this thumb switch works. I'm also thinking it's electrical because if I unplug the rear solenoid on the aux spool, nothing happens on the aux attachment when I push the aux button in the cab. I have not yet gone hunting for shorted wires, but I plan to do that this weekend. Other than that, I think I'm left either resetting or replacing the Electronic Control Unit (ECU) that I think the PWM is a part of. So one question is whether the PWM is part of the ECU or a separate box? I think its in the ECU but internet is unclear with some people talking about a PWM box. Next question is whether there is any way to calibrate or reset the PWM/ECU so that the aux spool centers in "neutral." I have pretty much thrown in the towel and have field service coming with a $900 ECU in about 10 days because they say they have to install it and program it. If anyone has an idea that can spare me that, would love to hear it. Thanks

 

[Tazza]

You replaced teh stems on the control block, did you change the coils too? I don't know how they get power, but if it's switched ground, there is a “possibility” the coil has a slight conducivity to ground, and when you enable the aux hydraulics, some of the power is grounding, making the coil energize partially?
I know it's a long shot, but you have replaced everything else that is not the main computer...

 

[chabel]

You replaced teh stems on the control block, did you change the coils too? I don't know how they get power, but if it's switched ground, there is a “possibility” the coil has a slight conducivity to ground, and when you enable the aux hydraulics, some of the power is grounding, making the coil energize partially?
I know it's a long shot, but you have replaced everything else that is not the main computer...

Thanks Tazza. Yes, replaced the coils (bobcat calls them solenoids) on the stems. Spent a couple hours the other day checking the + wires from both of those coils back to ECU to confirm first they had conductivity and were not broken and then that they had no connectivity to ground and thus were not shorting. All + wires checked out fine with multimeter. Then checked the - from each coil to make sure they had good connection to ground and those checked out fine. Never say never but at this point I think its got to be something in the ECU. I'd love to know if there is any way to factory reset the ECU. Assuming I can't figure that out, I am going to ask Bobcat tech if he can do it first before I have to eat the cost of an ECU. Regardless what happens I will post the ultimate resolution so I can hopefully spare someone else a little cursing and some brain cells.

 

[Tazza]

Thanks Tazza. Yes, replaced the coils (bobcat calls them solenoids) on the stems. Spent a couple hours the other day checking the + wires from both of those coils back to ECU to confirm first they had conductivity and were not broken and then that they had no connectivity to ground and thus were not shorting. All + wires checked out fine with multimeter. Then checked the - from each coil to make sure they had good connection to ground and those checked out fine. Never say never but at this point I think its got to be something in the ECU. I'd love to know if there is any way to factory reset the ECU. Assuming I can't figure that out, I am going to ask Bobcat tech if he can do it first before I have to eat the cost of an ECU. Regardless what happens I will post the ultimate resolution so I can hopefully spare someone else a little cursing and some brain cells.

You sure have done everything possible to try and find the cause, i hope it's not the ecu, but there really isn't anythig left is there?
One thing to try, very long shot is to disconnect the alternator, just in case there was bad diode or something, it could be messing with the ECU. It's just one plug on the back of the alternator. I highly doubt it, but any power issues could mess with a computer.
Totally grasping at straws for ideas at this stage.

 

[chabel]

You sure have done everything possible to try and find the cause, i hope it's not the ecu, but there really isn't anythig left is there?
One thing to try, very long shot is to disconnect the alternator, just in case there was bad diode or something, it could be messing with the ECU. It's just one plug on the back of the alternator. I highly doubt it, but any power issues could mess with a computer.
Totally grasping at straws for ideas at this stage.

Tazza and anyone else who follows, to close this thread . . . so I had the Bobcat field tech out. He plugged into the computer and it indicated the detent switch (the index finger switch on the front of the right joystick) was permanently on. Didn't change at all if we played with the switches. He tried to upgrade software on my old ECU and that did not solve it. So he put new ECU on and set it up for my machine. That solved the problem. I guess the good news is I have basically rebuilt every component of the Auxiliary hydraulics now so hopefully no more issues with that for years to come..

 

[Tazza]

Tazza and anyone else who follows, to close this thread . . . so I had the Bobcat field tech out. He plugged into the computer and it indicated the detent switch (the index finger switch on the front of the right joystick) was permanently on. Didn't change at all if we played with the switches. He tried to upgrade software on my old ECU and that did not solve it. So he put new ECU on and set it up for my machine. That solved the problem. I guess the good news is I have basically rebuilt every component of the Auxiliary hydraulics now so hopefully no more issues with that for years to come..

Shame it turned out to be the controller, but at least you know it's right now, no reason why it won't run essentially forever now