Power Antenna Relay
If the mast is not bent or broken, I think the problem is the antenna relay. If you want to disable the power actuation of the antenna, you can disconnect the under-dash relay without having to go into the fender well. The relay is a cigarette box-sized thingy that's mounted on the inside firewaill behind the brake pedal.
Put the antenna in the position you want to keep it (up or down) and unplug the relay. The antenna will still provide signal to the radio, just won't go up & down. Then, you can plug the relay back in if you want to power the antenna down for a car wash, etc.
I'm trying to find a source for replacement relays....if you know of any, please post. Thanks.