90 tbi firebird. fan comes on when moving a/c selector to an a/c position. aside from that it won't cycle thermostatically. Removed green wire from sensor and grounded it and fan came right on. Now question is, is the switch for sure bad or is this wire run into the ecm and my ecm is randomly not seeing a signal. Just want to be sure it's actually the switch before removing it since it's a hassle in itself.I realize the fan only comes on at high 220+ temps but my car will go to boiling over and it's fan will never come on. Switch was replaced like 2 months ago for same reason and now the car is doing the same thing. Do these switches really go bad this quikly. Or am I dealing with something that is damaging the switch? My connector looks perfect and no hacking has been done to the harness.