i have a 1999 genie manlift that i bought from iron planet (las Vegas) It worked good until late fall when it got cold then the brakes started to lock on me. it started out with just one locking and if i wiggled the joystick enough it would break free and work ok. eventually it got worse and both are now stuck on and i have to release the wheel hubs and tow it to move. Any ideas what it could be?
Welcome to HEF gillis. :drinkup We need to know the machine model and serial number.
sorry, model s-40, serial #3184
The brakes are spring applied, it takes hydraulic pressure to release them. The pressure to release brakes comes from the charge pump that feeds drive pump and is controlled by a solenoid valve. As long as the machine tries to drive/load engine when you work drive joystick, likely charge pump is good and developing pressure necessary to work brake release. Start checking the electrical. When you operate joystick controller, fwd or rev, you should see voltage on terminal 1 of controller, white/red wire. That wire goes to the solenoid valve, check if voltage is getting to solenoid valve, also check ground at solenoid valve. If charge pump pressure is good, voltage and ground at solenoid is good, could have a failed solenoid coil or valve spool, and could also be seal failure in rotary swivel causing loss of pressure to release brakes.
What is the connection between charge pump pressure and voltage and ground at solenoid being good?
I'm saying if charge pump pressure is good, which if machine loads engine and tries to drive when you operate the controller, it's likely good. If you have verified voltage at brake control solenoid when you operate drive controller is good. If you have verified ground at brake control solenoid is good. Then other possible problems could be faulty brake control valve solenoid or valve cartridge, or faulty seals in center rotary joint causing loss of pressure to release brakes.
Charge Pressure is used, among other things, to release the brakes. The charge pressure should be 360psi. This pressure is directed to the brakes through the brake valve. If the charge pressure is too low or if the voltage at the brake valve is too low or not there, then your symptom will be evident. There is a pressure test port on the drive pump that will let you connect a pressure gauge to (0 to 5000psi). Connect the gauge and start the engine. 360psi should be present. (The 0 to 5000psi gauge is in case the joystick is pushed while the gauge is hooked up. The pressure could soar to 3500 immediately). If the pressure is less than 250, brake issues can develop. If this pressure is ok then the next point of concern in the circuit is the brake valve. We need to verify there is at least 10volts at the brake valve when the drive joystick is stroked. 12volts is better but the valve should open at 10 or so. As Willie said, there should be 12 volts at terminal 1 of the drive joystick when it is stroked either direction. If there is, the next point to check will be terminal 32 of the terminal board in the upper control box. The next point to check there is at terminal 32 in the lower control box, and finally at the valve coil itself. If there is no voltage at terminal 1 of the drive joystick when stroked, check the angled micro-switch on the joystick. This is the brake release switch. If the voltage is ok, the solenoid coil will need to be checked out. With engine off, remove the brake valve cartridge from its block. Install the coil to the cartridge, apply 12 volts to the coil and verify the cartridge spool is moving in the cartridge. This will probably be as far as you need to go before you find the problem. If not, it will get a bit more of a challange. This machine was built before the usage of divider-combiner valves in the circuit. They used flow regulator and flow control valves in the drive manifold. What appears to be brakes locking up can actually be flow that is blocked from a motor or flow added to both sides of a motor at the same time. This happens when the valves in the manifold stick. The drive manifold is the lowest hydraulic assembly in the system so it is where all the water and debris settle. Very prone to causing problems of this nature on older machines or machines not well maintained. We will cross that bridge when we come to it
Thankfully...the Cavalry has arrived.
yeah, like in "F-Troop"! :tong Here is a photo of the joystick's switch side: