trane TUE060 furnace won't start
I was unable to find a similar problem in previous posts. I have a Trane TUE060 furnace. The furnace is not turning on when I set the temperature below the ambient temp. The AC functions properly and the blower fan runs when I switch to fan "on" mode (not heat mode). I'm getting an error code of three flashing red lights indicating pressure switch problem. The filter was just replaced. Based on other posts, I checked the tube behind the pressure switch and the exhaust fan turns freely. I also temporarily removed the exhaust tube to rule out blockage. I hope I didn't damage anything in doing so, but I also pushed back the plunger on the pressure switch with a screwdriver while holding the panel safety switch down. Still nothing. The unit doesn't seem to be doing anything (no hums or clicks...heard a click the first time I took the panel off and tried to start holding safety switch). Is it worth it to replace the switch ($45) before calling a professional? I don't have a voltmeter (and don't know how to use one anyway). Sidenote, the AC needed a charge last spring and there was considerable leakage of water down the unit when the ice melted off the coil (wonder if that damaged anything). Thanks in advance!