I have a 2005 grand marquis the wipers blades come on themself while driving the swicth is off

The wiper arm.

probably need nylon inserts in arms...auto parts store

You need to take the plastic cowls off that cover the wiper arm linkage and wiper transmission to inspect it...cowl is held on with 3 Phillips screws near windshield and some one inch wide metal clips, take off the gasket that fits on top. If both are not working check the transmission where linkages attach, if one wiper blade is not working it is usually the drivers side where the nylon bushing that forns a ball/socket sort of connection fails due to build up of debris and the rusting of parts that follows, let me know if this helps.

We have the same problem on our 97 Grand Marquis. We have replaced the wiper blades and the drivers wiper arm with a used one. The problem was not completely solved but it did work better. We are going to replace the arm with a new one and see if that works better.

bad wiper blade or wiper arm

If your'e just removing the wiper blade, check for a "release lever" where the wiper attaches to the arm, push (or pull) the lever and pull down on the blade at the same time. Do the opposite to install, except you do not have to push the release lever.
If you are removing the whole arm, there is a special tool that you slide under the arm that releases it from the 'gear'.

this is a very common problem on these vehicles. the wiper motor has a park switch built into it that fails. replace the wiper motor and this will stop problem. hope this info helps you!

go to link

http://www.streakfreewiperblades.com/site/990209/page/561743

Its the intermittant/park relay.

Yes the spring in the arm is weak, replace the arm and your problem will be solved.