Rheem R96VA0702317MSA Error Code 59: Water Sensed
What Does Code 59 Mean?
Error code 59 on the Rheem R96V means the control board has detected water in the collector box area. This is a critical fault — gas heating is disabled to prevent water damage, but cooling and fan modes still work.
As a high-efficiency condensing furnace, the Rheem R96V produces condensation during normal operation. This water is collected in the collector box and drains out through a condensate drain line and trap. Water sensors on the control board (pins 1 and 2 of connector P4) monitor for water accumulation. If current flows through these sensors for more than 10 continuous seconds, the control board declares code 59.
The most common cause is a clogged condensate drain line or trap that prevents water from draining properly. Over time, algae, mineral deposits, or debris can block the drain. When the drain is blocked, water backs up into the collector box and triggers the sensor. If left unaddressed, water can overflow and damage the furnace or surrounding area.
Common Causes
When to Call a Professional
Contact a licensed HVAC technician if:
- Code 59 returns after clearing the drain line
- You see water pooling inside the furnace cabinet or around the base
- The condensate drain line is frozen and cannot be thawed safely
- The collector box appears cracked or damaged
- You suspect the water sensor wiring may be damaged or touching sheet metal
Sources
✓ Verified against manufacturer service manual — March 2026