Where is the turn signal flasher on a 2000 ford windstar
 

There are 6 relays under the dash - which one is the flasher?

Only a suggestion, go to your nearest auto parts supply store and purchase a flasher for your vehicle. They have the listings for them. Once you have the flasher , you will now know what it looks like and it is different from other relays. If you remove the relays from the panel one at a time you will see the one that looks like the one you purchased.
A good idea is to locate the flasher by sound when it is working and mark it. Then when it comes time to replace it , it's marked. They don't make any sound when they don't work.

flasher location for 2000 ford windstar
 

It is part of the signal switch, a blue relay that can be removed by lifting the upper cover on the steering column.