1989 power antenna trouble
 

I am having trouble with the antenna motor on my 89' w124. The antenna will go up when the radio is switched on but will not retract when turning the radio off. I have opened the cover and was able to manually retract the antenna. The mast is fairly new and there are no obstructions in the way. Has anyone encountered this problem and if so what is the resolution short of purchasing a new unit.

Thanks,

Sam