It sounds like a wire problem.
You may need to call out a pro.
This can be done by do it your selfers, but it can be tricky with out the right tools. It can be tricky even with the right tools.
But it can some times be very easy.
I know that is not much help.
Good Luck!
It is very important that all wire connections be made with a water tight connection, often installers try to save a dollar by not using good connections.
Some installers make splices at the controller to the field wires.
This is a good place to start checking or redoing the splices with good connectors.
If you know how to use a mulitimeter and check the wires with it at the controller, it can save you a lot of time and money.