There's a six-terminal relay called the Evaporator Temperature Regulator. It's a bit of a pain to get to as you have to remove the rear and center console to get to it. The ETM will help you in locating it.
Once it's out, you can apply the tests in the ETM to the socket it plugs into.
On Christ the solid Rock I stand, all other ground is sinking sand. (Edward Mote 1797-1874)