willie59
Administrator
Yes, open the platform control box. If you don't have a terminal block in there, I'm really gonna wonder what kind of machine you have. LoL
-
Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
JLG 40HA won't idle up after depressing the foot switch.
- Thread starter ksp
- Start date
grandpa
Senior Member
Sorry to throw a wrench into your train of thought atco, but my JLG throttles up too when you step on foot switch.......must be something you flatlanders don't need...bah ha ha
willie59
Administrator
willie59
Administrator
It's ok ksp, pics are still not working since forum bug from a couple weeks ago. Be patient, they'll get pics working as soon as they can. 
Instead of pictures I would refer you to page 4-26 of the parts manual. This is what I have for controls. There is no junction block inside like the other types of controls. I am also using the 7-6 and 7-10 electrical diagrams for troubleshooting. I got these from the JLG web site and downloaded them. The file name is "Parts_3120673-08-01-06_ANSI_English"
Last edited:
willie59
Administrator
Aw shucks...I had completly forgot that you and I had discussed your machine had hyd controls instead of electrical controls. :tong
Nevertheless, the throttle control wiring remains pretty much the same. The high engine is controlled by the orange wire in the 16/12 cable that goes from platform control box to lower control box. I still would like to figure out how your getting a mid engine speed, because that's not on the original diagram. Initially, I'm curious how many relays are in the upper control box, there should only be one, the drive creep relay. Also, is there anything connected to the Blk/Red wire in the 16/12 cable.
Nevertheless, the throttle control wiring remains pretty much the same. The high engine is controlled by the orange wire in the 16/12 cable that goes from platform control box to lower control box. I still would like to figure out how your getting a mid engine speed, because that's not on the original diagram. Initially, I'm curious how many relays are in the upper control box, there should only be one, the drive creep relay. Also, is there anything connected to the Blk/Red wire in the 16/12 cable.
willie59
Administrator
Ok.
I'm trying to noodle out how your getting a mid range engine rpm. This is just a starting point. All the wires on the 16/12 cable are being used by something, except the blk/red wire. Maybe they have the footswitch connected to it and it's sending a singnal to something to throttle it up a bit. But thats the next problem...how? Without a mid range board, I gotta figure out how you are obtaining a mid range speed with you Precision Governor control box. We'll dig around here and see if we can figure this one out. Plus, your just learning a little bit more about your machine.
willie59
Administrator
I'm looking at the wiring diagram and see that the 12/4 cable has a +12v to platform. Can I assume this supplies all the power to the platform controls? If I read this right the wire supplies volts to the circuit breaker then goes to the footswitch and to the ignition back on the 12/4 wire. The yellow wire on the foot switch when depressed supplies + power via the yellow wire to the creep relay and pin 3 "voltage supply". Wher does that go? Would that be the drive controller? Trying to figure out the flow and orign of electricity. Also, what purpose do the diode and capacitor serve?
Thanks again for your help.
Thanks again for your help.
Last edited:
willie59
Administrator
Yep, you are reading it correctly.
Let's see if we can help you out in reading JLG diagrams, as they are not the easiest out there to read.
The 12/4 (which means 12 gauge wire, 4 conductors or wires) has red wire to supply battery voltage to horn at platform. That way if something was to fail with the igintion circuits or wiring, the horn has it's own power supply so you can sound the horn and get someones attention. Orange wire is power supply to platform controls. Blue wire is ignition wire, it sends ignition voltage back down to lower control box to power up the machine and engine. Black wire is ground (earth) for platform controls.
Power on the orange wire goes to the E-Stop switch, the E-stop sends power to the circuit breaker at platfom, then the power goes back to lower controls for iginiton, and it sends power to the foot switch using another 12/4 cable on the orange wire. The footswitch basically does three things. 1) it powers all platform electrical/hyd controls, making it a deadman switch. For example, if you were driving the machine, and removed your foot from the foot switch, the machine would stop, 2) It prevents you from operating the engine starter while foot switch is depressed and operating the machine. So you can only operate engine starter with foot off of foot switch, and 3) it prevents platform controls (such as drive controller) from operating while footswitch is up during engine cranking mode. When you depress foot switch, it sends power via yellow wires to creep relay and to pin #3 of the PQ drive controller harness plug. That provides power to the PQ controller. The resistor and diode in the yellow "power" circuit is to bleed off residual power after you release foot switch so it becomes a dead circuit. The yellow wire at the creep relay terminal 86 is to power the magnetic coil in the relay, but the relay needs ground to activate. Terminal 85 of the relay goes to lower control box via brn/blk wire. The brn/blk wire goes through the Tower boom stowed switch and the upper boom stowed switch, then to ground (earth) at lower control box. This provides ground for the creep relay when the tower and upper boom are down. If you raise either, it takes ground away from the creep relay causing the machine to drive in slow speed only.
Another thing the yellow circuit from the footswitch does is power up the dump valve at the machine turntable. It does this via a red wire from the 16/12 cable connected to the yellow circuit at the steer switch. The dump valve is what prevents you from operating the boom functions by using the control levers unless you have your foot on the footswitch. Which "may" be what is causing your throttle to rev up, something connected to the dump valve circuit at lower controls. Even then, I'm not sure how it would be sending a signal to the Precision Governor control box and which model Precision Governor box you have. It originally would have been equipped with an E-301 control box.
Let's see if we can help you out in reading JLG diagrams, as they are not the easiest out there to read.
The 12/4 (which means 12 gauge wire, 4 conductors or wires) has red wire to supply battery voltage to horn at platform. That way if something was to fail with the igintion circuits or wiring, the horn has it's own power supply so you can sound the horn and get someones attention. Orange wire is power supply to platform controls. Blue wire is ignition wire, it sends ignition voltage back down to lower control box to power up the machine and engine. Black wire is ground (earth) for platform controls.
Power on the orange wire goes to the E-Stop switch, the E-stop sends power to the circuit breaker at platfom, then the power goes back to lower controls for iginiton, and it sends power to the foot switch using another 12/4 cable on the orange wire. The footswitch basically does three things. 1) it powers all platform electrical/hyd controls, making it a deadman switch. For example, if you were driving the machine, and removed your foot from the foot switch, the machine would stop, 2) It prevents you from operating the engine starter while foot switch is depressed and operating the machine. So you can only operate engine starter with foot off of foot switch, and 3) it prevents platform controls (such as drive controller) from operating while footswitch is up during engine cranking mode. When you depress foot switch, it sends power via yellow wires to creep relay and to pin #3 of the PQ drive controller harness plug. That provides power to the PQ controller. The resistor and diode in the yellow "power" circuit is to bleed off residual power after you release foot switch so it becomes a dead circuit. The yellow wire at the creep relay terminal 86 is to power the magnetic coil in the relay, but the relay needs ground to activate. Terminal 85 of the relay goes to lower control box via brn/blk wire. The brn/blk wire goes through the Tower boom stowed switch and the upper boom stowed switch, then to ground (earth) at lower control box. This provides ground for the creep relay when the tower and upper boom are down. If you raise either, it takes ground away from the creep relay causing the machine to drive in slow speed only.
Another thing the yellow circuit from the footswitch does is power up the dump valve at the machine turntable. It does this via a red wire from the 16/12 cable connected to the yellow circuit at the steer switch. The dump valve is what prevents you from operating the boom functions by using the control levers unless you have your foot on the footswitch. Which "may" be what is causing your throttle to rev up, something connected to the dump valve circuit at lower controls. Even then, I'm not sure how it would be sending a signal to the Precision Governor control box and which model Precision Governor box you have. It originally would have been equipped with an E-301 control box.
Thanks for the info, it cleared some things up for me. My diagram is so hard to see that I can't tell sometimes what the wires are intended to operate.
It would make things a lot easier if I had a diagram that I could read.
With this info in hand I'll take a look again and see what I can discover when I get time.
My platform cover is screwed up so it is rather difficult to get it off without messing the thing up but will look at it this weekend. I am in the middle of a house remodel and work with it as time allows.
I need to finish the kitchen wiring and ceilling.
I really appreciate your help on this.
It would make things a lot easier if I had a diagram that I could read.
With this info in hand I'll take a look again and see what I can discover when I get time.
My platform cover is screwed up so it is rather difficult to get it off without messing the thing up but will look at it this weekend. I am in the middle of a house remodel and work with it as time allows.
I need to finish the kitchen wiring and ceilling.
I really appreciate your help on this.
I have been looking at the diagram and was wondering if you could expand a little on how the foot switch works?
1) Why are the yellow and black wires crossed over from side to side?
2) How does the circuit work to choose between high and low speed?
I'm getting there!!
1) Why are the yellow and black wires crossed over from side to side?
2) How does the circuit work to choose between high and low speed?
I'm getting there!!
willie59
Administrator
I'm not sure how your changing engine speed with foot switch, trying to figure that out myself. My best guess is engine governor control is somehow connected to the dump valve circuit, the red wire connected to steer switch.
As for the foot switch operation, there are two switches inside the foot switch housing. Each switch has three terminals and they are described using terminology that is common when describing electrical switchs, relays, contacts, etc. One terminal is called C (Common), the other two are called N O (Normally Open), and N C (Normally Closed). The term Normal is used to described any switch, relay, or contact when it's not activated, such as when the engine is off and machine is not in use. All schematics are drawn in the "machine off" position. In the case with the foot switch, Normal would be when the switch is not depressed. The Common terminal of a switch or relay connects to either the N O, or N C terminals of the switch/relay depending on whether they are being activated or not. The N O and N C terminals never connect with each other. In the case with the foot switch, you can see on the diagram the orange wire sends power to the first switch at the C terminal of that switch. So with foot switch in Normal position (not being activated/depressed) the power at C terminal would be connect to the N C terminal being it's the close circuit. The N O is the open circuit in this position. The blue wire for the engine starter circuit is connected to the N C terminal, so in this position, you can start engine. At the same time, the red wire is connected to the N O terminal, this is the circuit for powering up controls at platform. Since it's on the open circuit in this position, there's no way you can operate machine functions while cranking engine. Once you have machine running and are going to operate it, you step on foot switch. Now things are not in there "Normal" position, which means things reverse. The N C is now the open circuit, and N O is the closed circuit. Now, with foot switch depressed, the red wire has power on it to enable platform controls, and the blue wire has no power, so starter will not operate. You have to study it for a minute, but you'll figure out the jumper wires to the second switch. The second switch is connected to the ground (earth) terminal on C of the switch. The function of the second switch is simply to remove residual power from the starting and control circuits after you have used them. For example; your foot is not on foot switch. You crank engine with the power from blue wire. Once engine starts, there could be (theoretically) some residual voltage on the blue wire. When you step on foot switch to operate machine, this action connnects the blue wire circuit to ground (earth), draining any residual voltage left in that circuit effectively disabling it. Same thing happens with the yellow jumper. It removes residual voltage from the operating circuit while cranking engine by connecting operating circuit to ground.
As for the foot switch operation, there are two switches inside the foot switch housing. Each switch has three terminals and they are described using terminology that is common when describing electrical switchs, relays, contacts, etc. One terminal is called C (Common), the other two are called N O (Normally Open), and N C (Normally Closed). The term Normal is used to described any switch, relay, or contact when it's not activated, such as when the engine is off and machine is not in use. All schematics are drawn in the "machine off" position. In the case with the foot switch, Normal would be when the switch is not depressed. The Common terminal of a switch or relay connects to either the N O, or N C terminals of the switch/relay depending on whether they are being activated or not. The N O and N C terminals never connect with each other. In the case with the foot switch, you can see on the diagram the orange wire sends power to the first switch at the C terminal of that switch. So with foot switch in Normal position (not being activated/depressed) the power at C terminal would be connect to the N C terminal being it's the close circuit. The N O is the open circuit in this position. The blue wire for the engine starter circuit is connected to the N C terminal, so in this position, you can start engine. At the same time, the red wire is connected to the N O terminal, this is the circuit for powering up controls at platform. Since it's on the open circuit in this position, there's no way you can operate machine functions while cranking engine. Once you have machine running and are going to operate it, you step on foot switch. Now things are not in there "Normal" position, which means things reverse. The N C is now the open circuit, and N O is the closed circuit. Now, with foot switch depressed, the red wire has power on it to enable platform controls, and the blue wire has no power, so starter will not operate. You have to study it for a minute, but you'll figure out the jumper wires to the second switch. The second switch is connected to the ground (earth) terminal on C of the switch. The function of the second switch is simply to remove residual power from the starting and control circuits after you have used them. For example; your foot is not on foot switch. You crank engine with the power from blue wire. Once engine starts, there could be (theoretically) some residual voltage on the blue wire. When you step on foot switch to operate machine, this action connnects the blue wire circuit to ground (earth), draining any residual voltage left in that circuit effectively disabling it. Same thing happens with the yellow jumper. It removes residual voltage from the operating circuit while cranking engine by connecting operating circuit to ground.
ahhh. makes sense when you explain it that way. You certainly have a gift in that you are clear and concise when you write. This will help a lot when "looking under the hood".
Can you explain how it works to go between low and high ground speed?
This thread my have to be a sticky!!
Can you explain how it works to go between low and high ground speed?
This thread my have to be a sticky!!
willie59
Administrator
Well, thanks for the compliment ksp, but I'm just trying to help you learn how to read schematics. Clear and concise is necessary in that respect.
Hi and low ground speed? Do you mean drive speed or engine speed? Or, if you mean that mid engine speed, I'm still trying to figure that one out.
Hi and low ground speed? Do you mean drive speed or engine speed? Or, if you mean that mid engine speed, I'm still trying to figure that one out.
willie59
Administrator
Ok, drive speed. It's complex, yet simple. Hi speed drive is achieved by simply applying maximum current (voltage) to servo on drive pump via output from PQ controller. Creep (low speed drive) is achieved by reducing, or limiting, the current to the drive pump servo. The complex part of it is the output of the PQ controller. It's not an output you can measure with a voltmeter because the output is Pulse Width Modulation (PWM). This means, the PQ controller sends a voltage signal that is "fully on, then fully off, fully on, fully off". So, hi drive would be a signal that is "fully on" for a wide period of time and "fully off" is a short period of time, causing the pump servo to provide maximum output of the drive pump. Creep would be a short burst of "fully on" and a wide period of "fully off" to lessen the degree of pump output. Not easy to explain this operation.