I had a problem with my antenna not wanting to go back down after it had been extended. Inside the case of the antenna is a relay that switches the direction of the antenna motor. The contacts in this relay get eroded over time which then has problems making good contact thus causing no current to flow. In my case it was the contact for the retract circuit. Disassemble the antenna and release the antenna's relay. It's mounted inside the cover where the ribbon gets coiled up. You have to pry off the plastic cover on the relay to access the contacts. They can than be cleaned with a small nail file.
I cleaned mine 2 times in a 3 month period but the problem came back. I then researced power antenna's and found a replacement antenna that is exactly like the original Acura antenna from a place in Miami called Antennnaworld.com. Their service was good and a complete antenna is available for approx. $125 VS. $450+ from Acura. You will however need to be mechanically inclined because there are some minor mods that need to be made. If you need some assistance, let me know and I can talk you through it.