jlg 40e "procedure fault"
I hope the Jlg experts out there can help me with this one. JLG 40e worked great until last fall when it just stopped responding. Flash code on controller was one flash, internal fault. Controller replaced, batteries replaced, but unit still will not go fwd/reverse or move boom, (except that all boom controls DO work if function selected and then steer switch applied.) I guess this verifies that the pump and hydraulics are good, but something wrong with controls. I note that the controller flashes 2-flashes when the foot switch is pressed, even if no control input is selected. Strange. Steering function OK, drive motors- nothing.
I have multimeters and am pretty good at troubleshooting but I can't figure this out. Any ideas?
The Steer Override Contactor (pump bypass) bypasses the Motor Controller.
When Steer is activated, power for the steer contactor comes from the Steer Output of the Drive Joystick, through a couple diodes and to the Steer Overide Contactor on a Gray/Black wire. This circuit is functioning ok as the steer function is working properly.
The FWD, REV, and PUMP (changeover) Contactors, Elevation Limit Switches, Tilt Sensor and Brakes get their Battery + from the 7 Amp Fuse that is located on the Tach Interface Board via the White/Red wire. The Steer Contactor does not. (remember the Gray/Black wire)
The Battery - (minus) is provided by the Motor Controller to the individual contactors when selected. Except the Steer Contactor Coil is wired directly to Battery - of the Motor Controller.
Without this Battery +, there will be no Drive, Boom Functions or Brake Release.
Let's begin by checking to see if there is +48 volts at both sides of the 7 Amp Fuse.
If the 7 Amp Fuse has +48 volts on both sides then we will need to check the White/Red wired circuit pointed out in the schematic.
Do not overlook Diode D1 on the Tach Interface Board. Check at terminal 16 of the terminal strip of the Tach Interface Board.
If there is no voltage at the fuse, then we will need to investigate further upstream.
There is also a 20 Amp Fuse on the Interface Board but that is good. If it was not good, steer would not be working.
The 20 Amp Fuse feeds the E-Stop Switch. We know that is working.
The Tach Interface Board is located in the Drive Motor Compartment just to the Left of the Motor Controller.
More about this machine from an earlier episode:
Can this thread be moved to "other construction equipment......." forum?
Tool Carrier people don't want to read about JLGs
I'm on it. Please move to anywhere... I just posted here because the search led to the other JLG 40 question.
OK, here's what I have so far. With pedal depressed and any boom function switch activated, I have +48 at both sides of 7 amp fuse, at terminal 16 of the strip on the tach interface board (with it still plugged in), at the red/white connectors on the drive reverse contactor, and at the red/white connector on the change over relay. (The blue wire at the change over was zero.)
Check for a ground at the Blue wire on the Changeover Contactor when a function switch is activated. Lift Up for instance
Also, before I forget,
Is the Main Contactor turning on?
Never mind...thinking in circles...if the Main Contactor wasn't coming on, the Steer would not be functioning...disregard the Main Contactor question
I see you checked the blue wire already.
Follow the Blue wire back to pin 1 of the 17 pin connector of the Motor Controller.
It should be energized when a function is selected
Last edited by VoodooMojo; 04-28-2013 at 03:21 PM.
The Main Contactor supplies power to the Motor Controller.
There should be about +48 volts on the Battery side of the Main Contactor (big lug) and about zero on the Motor Controller side. If the Main Contactor activates, there should be about +48 volts on the Motor Controller side as well.
When the Main Contactor is deactivated, the power on the Motor Controller side should slowly decrease back to about zero volts. (Capacitors in the Motor Controller take awhile to discharge)
Yes, it is -48 in that situatiuon. I can feel it/hear it engage when I remove and replace the blue wire. You are talking about contactor #1 in your picture illustration above, right?
The Changeover Contactor determines if the output of the Motor Controller goes to the Drive Motors or the Pump Motor.
There will be power on the Blue wire of the Changeover Contactor when a function is selected and there will be no power on the Blue wire when Drive is selected
# 1 is the Main Contactor
Originally Posted by bluegrass
# 2 is the Changeover Contactor
# 3 is the Steer Bypass Contactor
OK, we are on the same page. The contactors are labaled incorrectly in my JLG parts book!
When pedal is depressed, output of main is energized. I also checked downstream of 200A and 80A fuses, and both are energized with pedal depressed.
Follow carefully the pretty colored wires on the drawing of the big lug circuitry.
It is easy to get them mixed up.
Follow wire for wire with your machine
WOrking on it. Odd... started with changeover via output from terminal A on controller. Pedal not depressed, output to pump motor is -48 (and zero to traction motors). Pedal depressed, zero to pump motor and -17.5 volts to traction motors(??) Control inputs have no effect on either.
I will chase the other wires, too.
Depending the state of motor controller capacitor charge, we can get some pretty funky readings when diagnosing this circuit.
Originally Posted by bluegrass
The A terminal will be giving out a pulsed (PWM) negative signal when it is driving or lifting.
Looks like we are on rain delay now. Thank you so much for your help so far. I will get back on it when it isn't raining and continue the saga...