Dear PA24 driver,

Hope you're well. Here's the link to the FAQ section dealing with the control board, in the climate control unit: https://www.brickboard.com/FAQ/700-900/HeatingAirConditioning.htm#MCCClimateControlACNotWorking .

You're correct. The circuit board in the climate control unit is behind the front panel, on which are the three knobs that control: fan speed, air flow direction, and temperature.

The solder joints develop micro-cracks - too small to be seen with the unaided eye - as a result of repeated on-off cycles (heating and cooling). Eventually, the solder fatigues, and cracks.

To avoid missing a micro-crack, touch the tip of a soldering iron (not more than 40 watts; 25 watts is ideal) to each joint where the relay's pins go through the board, and on the main connector. If I recall correctly, there are 13 pins on the main connector.

When the solder changes color - from dull gray to shiny silver - the solder has liquefied. That closes any micro-cracks.

Hope this helps.

Yours faithfully,

Spook