Keep wet or damaged equipment off and correct the ingress path before service.
If water, corrosion or moisture damage is found inside a snow-melt controller, de-energize the affected equipment and have a qualified electrician inspect it. Do not reach into an energized enclosure or repeatedly power wet electronics to see whether they recover.
Inspect the enclosure, mounting location, cable entries, conduit path and seals against the exact controller’s installation instructions and enclosure rating. The presence of a top conduit entry alone does not establish the cause; water can enter by more than one route.
Use fittings, drainage and sealing methods permitted for the equipment and electrical installation. Generic expanding foam or silicone is not a universal listed conduit-sealing method. Correct the moisture source before installing replacement equipment.
Have the manufacturer or qualified service provider determine whether the affected controller must be replaced. Do not assume an undamaged appearance proves the circuit board safe, or transplant instructions between SCP-120/APS-3C and SCA-DUAL models.
Source for the SCP-120 arrangement: SCP-120 / APS-3C installation manual.