Hydro-Quip Gecko 4-Pole 3 Wire Hi Limit Sensor with 1/4 Inch Bulb, 34-0201

The Hydro-Quip 34-0201 is a hi limit sensor for Gecko spa controls. It uses the Gecko 4-pole 3 wire connector, has a 1/4 inch sensing bulb and a 14 inch lead.

What it protects

The hi limit is the safety sensor at the heater. It is not the one that holds your set temperature; its job is to notice when the water at the heater has gone past a safe point and shut the heater down before anything is damaged or anyone is scalded. Because it is a safety device, a spa will refuse to heat rather than run without a working one.

The symptom that leads here

Repeated overheat or hi limit faults on a spa whose water is plainly not hot. A sensor that has drifted out of range or failed open reports a temperature that is not real, and the controller does the safe thing and locks the heater out.

Getting the right one

The connector is what matters most. Count the poles and wires on the sensor you are removing and confirm it is the Gecko 4-pole 3 wire style before ordering.