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JLG 40 HA LIFT Brake question

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Kohl

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Jul 1, 2020
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6
Location
Nesquehoning PA
I’m hoping somebody might know the answer to this. We have a JLG 40 HA lift and the front wheels are locked. You can hear the motors trying to turn but the breaks will not disengage. I believe they are a hydraulic drake? Can someone tell me where the release valve or solenoid is located so I can check it and try to disengage the breaks please?

Thank you!!

Kohl
 
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Alberta, Canada
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HD Mechanic
The brakes are spring applied and hydraulically released. make sure you have hydraulic pressure getting to those two drive motors. There is a little cap on the center of each drive motor, held on by two 1/4" bolts (7/16 head). They have a dimple usually pointed outward. Remove these caps and turn the dimple inward, then re-tighten the bolts. This will release your brakes on those hubs. it will also disconnect the drive motors on those two hubs.
 
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Kohl

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Joined
Jul 1, 2020
Messages
6
Location
Nesquehoning PA
Is there anyway to release the brakes but keep the motors active so we can test it to see if it will move?

The overall problem is when you move the stick you can hear the hydraulic pump load up but then just bogs the motor and doesn’t move. I tried moving the small plastic lever on the pump solenoid and it bogs down the same exact way.

How can I test that I’m getting fluid down to the drive motors? I’m hoping it’s not the pump now. Was thinking it was just the brakes but I’m guessing there’s no valve that controls the release of the breaks?
 
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it is 4wd, correct? Your drive motors on the solid axle are still working while the drive motors on the steer axle are locked?

I have no access to JLG information at this time, but I suspect that whatever switches from 4wd to 2wd is malfunctioning. Not sure what that device is or where it might be located. I believe manuals are available for the 40HA from the JLG web site still. If you don't have manuals for this machine, it might be a good time to get them.

Looking at the locked drive motors, there should be 3 or 4 hydraulic hoses. Two larger ones, and one or two smaller ones. One of the smaller hoses will be the brake, other other small hose will be a "case drain" going back to the hydraulic tank. The brake hose will be going to a location closest to the wheel. You can follow that hose back and see where it goes to.
 
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Kohl

Member
Joined
Jul 1, 2020
Messages
6
Location
Nesquehoning PA
It’s a 2 wheel drive model. We did actually track the break hose back and found it ran to a solenoid. If we powered that solenoid directly it would unlock the brakes. So we tracked it farther and found it went to a Bosch relay. When we tested it there we weren’t getting any control voltage so we chased that wire down to terminal block 22. At that point we saw that the wire ran all the way back to the basket. So we went there next and found that wire on terminal 22. Weirdly enough there was no wire coming out of the other end of 22. We scratched our heads for a while and second guessed ourselves until I looked at the terminal directly next to it. I found a wire broken off and tucked under the other ones. Followed it back and it went to the stick. We tested the stick to that wire and in forward or reverse discovered 12 volts. Tracked it back and eventually found that it powered the Bosch relay which in turn powered the break solenoid. So we basically found the problem but learned a whole bunch in the process so that’s a definite plus!! Thank you for your advice and I hope this helps someone else out in the future!!
 
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Kohl said:
It’s a 2 wheel drive model. We did actually track the break hose back and found it ran to a solenoid. If we powered that solenoid directly it would unlock the brakes. So we tracked it farther and found it went to a Bosch relay. When we tested it there we weren’t getting any control voltage so we chased that wire down to terminal block 22. At that point we saw that the wire ran all the way back to the basket. So we went there next and found that wire on terminal 22. Weirdly enough there was no wire coming out of the other end of 22. We scratched our heads for a while and second guessed ourselves until I looked at the terminal directly next to it. I found a wire broken off and tucked under the other ones. Followed it back and it went to the stick. We tested the stick to that wire and in forward or reverse discovered 12 volts. Tracked it back and eventually found that it powered the Bosch relay which in turn powered the break solenoid. So we basically found the problem but learned a whole bunch in the process so that’s a definite plus!! Thank you for your advice and I hope this helps someone else out in the future!!
Click to expand...

Good find!! You did well. That's pretty much how most JLG repairs go btw.
 
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