I posted this on the Pro area and thought to also try here.
I have a water cooled air handler with the old style of display. Nothing lights up on the display except the SET light which doesn't turn off. The unit runs but we had to disassemble the chill water valve to get it to cool. Both boards were changed and so was the panel. Could the unit be stuck in test mode?
the unit is an '83 model.
Also on the same type unit, the CWV is not opening on a couple units. I have AC voltage to the motor but no signal voltage. I replaced the temp sensor and still nothing. Where can I look further?