Watkins Control-Stat Thermistor 38415

 HotSpring Tiger River Control Stat Thermistor 38415

Watkins PN 38415 Control Thermistor for HotSpring and Tiger River spas (see Model List Below). Used in conjunction with the 38416 Hi-Limit Thermistor and the 73790 or 73791 No-Fault Heater. 

This control thermostat thermistor sensor detects the spa waters temperature and relays that information back to the system. It simply screws into the No Fault Heater Housing (hand tight only) and plugs into the side of the spas control box. This item is found on the 1995-2000 Hot Spring Classic, 1995-2002 Hot Spring Grandee, Jetsetter, Landmark, Prodigy and Sovereign. It was also used on the 1995-1996 Highlife, 2002 Sovereign ILE (Special Edition) and 2000-2002 Hot Spring Vanguard. This thermistor also found on the Tiger River 1995-1996 Khyber, Manora and Tondi and the 1997-2002 Siberian, Bengal and Sumatran spas.

Spa Models Using Hi-Limit PN 38415:

HotSpring: Classic 1995-2000; 1995-2002 Grandee, Jetsetter, Prodigy, Sovereign; 2001-2002 Vanguard

Tiger River: 1995-2002 Khyber/Siberian, Manora / Bengal; 1997-2002 Sumatran; 1195-1996 Tondi

Note: newer model spas 2003-current use Control Thermistor PN 39530

Related Item: Watkins  No Fault Titanium Heater:

73790  -- OR -- 73791

Note: Symptom of this part failing is fluctuating spa temperature even though the temperature setting has not changed. Symptom of this part failing completely is a flashing green "Ready" light on the control panel of a Hot Spring spa model. This thermistor is larger in diameter than the High-Limit Thermistor (38416).  It screws into the port (hand tight only) marked "Inlet" on the PDR replacement heater. Typically, when one thermistor needs replacing the other is close to failing and should be replaced at that same time. Thermistors have a reliable lifespan 6-8 years or so.

Test Procedure

1. Set the meter to 20K on the OHM scale.
2. Record the temperature of the spa water.
3. Unplug the thermistor from the control box.
4. Meter across the two Thermistor leads.
5. Refer to the Temperature versus Resistance chart below to find the correct resistance value for the temperature measured. If the temperature and resistance does not match that of the chart, this test has failed and the thermistor must be replaced. Remember if the spa has been inactive, the spa water temperature may be different
than the water temperature in the heater housing.