A/c unit not working. Temp gauge reads dashes.

My car a/c will turn off and stop cooling .
temperature gauge reads dashes ( just lines)...un
hook the battery and re-connect...will work fine.
Untill I shut car off..then ahve to do same stuff ove
again...anhway ive tried every thing possible. Spent
over 500$ and still not fixed...but also I have never
went to the dealer ship for the recall on....
  . Ignition... The switch...i promise other than
changing the a.c. and heater unit inside the car
nothing has solved the problem...but I am going to
go have the switch replaced...free because of the
recall...and if that fixes it. I will post a update.