Its for a 480V motor for a hoist. We got it from our Pittsburgh warehouse. They said it worked when they last used it When you press the up or down button the coil to the contactor sometimes energizes and sometimes doesn't. It pulls contacts in but immediately releases them. Like i said its intermittent that it even does this. It doesn't hold in long enough for the motor to start or something else is wrong. THere is 480V coming in and I wonder if there were a large voltage drop on the line would this be the cause of problem.
Call a qualified professional electrician to do the work. Somewhere in the circuit you have a bad connection that is in need of repair. Depending on the use of the hoist, I would suggest either sending it to the manufacturer for a complete overhaul or the purchase of a new unit. If this is a small weight rated unit, replace it, if it is a heavy duty one of 10 tons or more then a factory service may be warranted. Trying a DIY repair in this case is not a safe long term practice and may violate some OSHA regulations and could be very dangerous to any personnel using the unit. These motor hoists involve a locking brake system, a reversible motor and contactor in the unit and the control pendant. The problem could be nearly any location in the electrical system and if your maintenance department is not able to solve it, replace it.
Troubleshoot through the entire circuit. I would start with the push buttons first, you could have a problem with the buttons having intermittent contact... I have run across that several times. Next, check the connections on the coil and the starter. Depending on the size of the hoist, it may have a few interlocks, I would check those also. Most of the smaller hoists have a switch to prevent the hoist from going too high, this may have something to do with your problem as well. There may be several other things that could cause this, but this will be a good start. Please feel free to email me if you need any help or have any other questions.
