Secondary drain pan shut-off switch, Safe-T-Switch Model SSW, detects clogged A/C condensate drains and shuts off system to prevent water damage. With no moving parts to break or become clogged, the patent-pending SSW water sensor is placed directly into a metal or plastic secondary drain pan or on a floor. The logic circuit of the SSW continuously samples the sensor probes for the accumulation of water and determines if the presence of water is transient or permanent. When proprietary sensors detect as little as a 1/16-inch level of permanent water, the SSW water sensor automatically shuts the HVAC system down. A red LED on the top cover of the unit indicates that the SSW has been activated. After the water has cleared, the SSW water sensor will automatically reset.