1997 Mercury Sable will not start when turning key Makes no clicking noise no sound at all Everything else comes on radio windows etc Ran fine yesterday only has 80000 miles?

My limited knowledge tells me it may be the soleniod(sp?) or alternator. When my 87 Sable had that prob my friend get underneath the hood and 1)I turned the key in the ignition and held it engaged. 2)He tapped the alternator w/ a hammer. This allowed the clicking sound to happen. If I recall correctly, the clicking sound while knocking the alt meant the alt was bad. If no clicking happens when knocking the alt then the soleniod is bad. The soleniod is a lot easier to replace so hope it's that. I accept no responsibility if something breaks or this only makes the prob worse :)