Two wires from the relay are connected to a resistance sensing probe in the pump seal cavity and the grounded motor housing or across two probes to monitor the seal leakage using a low-voltage DC signal. If the seal starts to leak, contaminating fluid enters the seal cavity. This lowers the resistance between the internal probe and the common connection. When the resistance drops below a user-adjustable sensitivity set-point of the relay, the output relay energizes and the LED turns red. The relay output can be used to give an alarm indication of a leaking seal.