I have a newly installed Trane 4 ton xl20i, all factory matched components. Within days of installation I had the red light come on showing error code 90. Installer has been out numerous times to check wires, clean wires, change wires, check voltages, etc. Last visit a new factory shipped circuit board was installed and it worked fine for one day, but alas, now inop again due to error code 90. Now what? 02/09/2011