The fan works for weeks at at time but then stops. Then it will start working again within a few days. I think I must have a loose connection, but I don't know how to access it.

It may be a switch problem. Try spraying the switch with WD-40.

Thanks for your help. Where is the switch located?

On your control panel--it may be a button or dial. Oil and dirt from your fingers can cause problems. The WD-40 will act as a contact cleaner, moisture displacer, and lubricant. It's worth a try.

Before replacing switches, record any radio codes and disconnect the negative battery cable.