Mauldin MG622 drive issue

[SamsDuramax1026]

Hello everyone I’m new to this forum, thought maybe someone out there in the world would be able to shed some light on this problem we are having. Mauldin MG622 will not move. Runs fine, all hydraulic functions work fine, low hours, the machine just stopped all of a sudden. Drives are completely controlled electronically. We’ve ruled out everything possible that us and the folks at Mauldin can think of over the past few days. Anyone out there ever seen or heard of this issue? Please help - thank you!

 

[funwithfuel]

My experience lies with Volvo and champion. I have seen the FnR controller break the wires off right at the switch. Have they provided you with an electric schematic or a description of how it's supposed to work? I did not find anything other than parts on their website.

 

[SamsDuramax1026]

Thanks for the response. Yes I have a schematic. It’s a somewhat complicated system, the forward/reverse joystick sends signal to the dash monitor as well as the computer/drive controller. Dash monitor is showing it in forward/reverse and the gears as it should be. Computer is receiving the signal as well. Computer is then supposed to send signal to the electronic swash plate controls on the hydraulic pumps. We just don’t know if it is or is not. We understand the signal going to these swash plates is is milli-amps, and don’t know how to read those. However the wires for this circuit from the computer to the swash plate controls do check out fine for continuity. Kind of at a dead end road.

 

[funwithfuel]

Ok, so its hydrostatic? 2 opposing solenoids on a common valve? Do you have a DVOM ?

 

[SamsDuramax1026]

Yes hydrostatic. 2 pumps run off the engine, one drives the front 2 drive wheels the other the rears. Each of the 4 drive motors has the feed and return hose, mounted between each 4 there is a block with what they have called an anti-slip solenoid mounted in them. We have since tried to bypass this system and still no changes. Have even tracked down the previous owner who has said they had the same problem from day one with the machine, have replaced both pumps to no avail. The problem is definitely electrical. We do not have a way to plug into the unit. The computer has since been discontinued, however we don’t think the computer is a problem. There are LEDs that flash on the side of it and you count the order they flash in, we do have a schematic from Mauldin as to how to read these, the code boils down to one of the anti slip solenoids I mentioned being open or a bad solenoid, but again we’ve tried to bypass these with no changes. Again it’s as if the drive controllers on the pumps aren’t getting any signal. All wires in the whole system check out fine, so no opens or shorts anywhere.

 

[SamsDuramax1026]

Yes we have a digital multi meter

 

[funwithfuel]

You can back probe the connections carefully. Watch value in volts to pwm valves.
The other thing you could do is verify that there is no signal from the inching pedal. Basically in the brake pedal, there should be a valve that sends a signal to the hst pump to destroke. After verifying that the pedal is fully retracted and there is no trash keeping the pedal from returning you could follow the inching hose back to the pump, disconnect it and there should be no oil flowing while running. If it does, there's a problem, the inching pedal is telling the pump that your stepping on the brake.
Happy hunting.

 

[cuttin edge]

does it have a foot brake? We have the maintainer models. just a foot pedal with a cable to the side of the pump. push the top of the pedal to go forward, bottom for reverse take your foot off the pedal to stop. Only electrics are high and low range.

 

[SamsDuramax1026]

Thanks for the response. Completely different setup from the maintainers. This one is all electric controlled to the drive pumps. Only cable/mechanical part is the throttle pedal to the engine.