This problem is often caused by a faulty relay on the alarm module.
The module has three identical relays on it, one for the front wipers, one for the rear wipers, and one for something else. You can probably find a small 12V relay at your local Radio Shack. If not, Mouser Electronics (
www.mouser.com) sells everything you need.
Remove the alarm module (A & C module - under the glove box). You might also want to remove the keyless remote box and the support bracket to give you more room to work). Desolder the relays and install new ones. You'll need a small soldering iron (about a 40 Watt) with a pencil tip, a solder removal bulb (solder ******), some desoldering braid, and some rosin core solder. Be careful with the heat around other components on the board. Too much heat may damage one or more of the surrounding chips or relays. Once the new relays are soldered in, slide the board back into the plastic module, snap it together, and reattach it under the glove box.