Thermistor, Control Thermostat, Hot Spring and Tiger River

Item #: 38415
This item is obsolete and replaced by:
78970

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 outside of the spa’s control box. If your existing thermistor plugs directly onto the main circuit board (motherboard) inside the IQ2020 control box, then use item 39205. Always replace thermistors in pairs (ie; 38415 & 38416).

Description

This control thermostat thermistor sensor detects the spa water 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 outside of the spa’s control box. If your existing thermistor plugs directly onto the main circuit board (motherboard) inside the IQ2020 control box, then use item 39205. Always replace thermistors in pairs ( ie; 38415 & 38416 ). Check your serial number in the parts finder above to be sure this part is for your spa.

Note: Symptom of this part failing is fluctuating spa temperature even though the temperature setting has not changed. A 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 of 6-8 years or so.

Note#2: ALWAYS REPLACE THE THERMISTORS IN PAIRS. If a new thermistor differs in temperature sensing more than five degrees from the old thermistor, the system will go into a “fault mode” and prevent the heater, jet pump(s) and light from operating. So again, when replacing a control thermostat thermistor always replace the high limit thermistor as well and vice versa.

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 do 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.

Printable PDF

View Diagrams & Part Compatibility

Ref. Diagram
# 10 No Fault 5500 Cartridge Heater 1995-1996 (Hot Spring 1995 - 1996) View Diagram
Thermistors (PUG, ORCA, and EAGLE Compatible) (Hot Spring 1995 - 2000) View Diagram
# 8 No Fault Heater 1997-2002 (Hot Spring 1997 - 2000) View Diagram
brand model years
Hot Spring Classic (F) 1995, 1996
Hot Spring Classic 230v. (FH) 1995, 1996
Hot Spring Grandee (G) 1995, 1996
Hot Spring Grandee (GQ) 1996
Hot Spring Prodigy (H) 1995, 1996
Hot Spring Sovereign (I) 1995, 1996
Hot Spring Sovereign 230v. (IH) 1995, 1996
Hot Spring Sovereign 230v. (IHQ) 1996
Hot Spring Sovereign (IQ) 1996
Hot Spring Jetsetter (J) 1995, 1996
Hot Spring Jetsetter (JQ) 1996
Hot Spring Highlife (K) 1995, 1996
Hot Spring Summit (R) 1995, 1996
Hot Spring Landmark (S) 1995, 1996
Tiger River Siberian (L) 1995, 1996
Tiger River Bengal (M) 1995, 1996
Tiger River Manora 230v. (MH) 1995, 1996
Tiger River Tondi Round (P) 1995, 1996
Tiger River Tondi Round 230v. (PH) 1995, 1996
Hot Spring Classic (F) 1995, 1996, 1997, 1998, 1999, 2000
Hot Spring Classic (FQ) 1998, 1999, 2000
Hot Spring Grandee (G) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Grandee (GQ) 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Prodigy (H) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Prodigy (HQ) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Sovereign (I) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Sovereign 230v. (IHQ) 1996
Hot Spring Highlife Limited Edition (ILE) 2002
Hot Spring Sovereign (IQ) 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Jetsetter (J) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Jetsetter (JQ) 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Summit (R) 1995, 1996
Hot Spring Landmark (S) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Landmark (SQ) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Vanguard (V) 2001, 2002
Hot Spring Vanguard (VQ) 2001, 2002
Tiger River Siberian (L) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Tiger River Siberian (LA) 1997
Tiger River Khyber (LH) 1995
Tiger River Siberian (LQ) 1999
Tiger River Bengal (M) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Tiger River Bengal (MA) 1997
Tiger River Manora 230v. (MH) 1995, 1996
Tiger River Bengal (MQ) 1999
Tiger River Sumatran (N) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
Tiger River Sumatran (NA) 1997
Tiger River Sumatran (NQ) 1999
Tiger River Tondi Round (P) 1995, 1996
Tiger River Tondi Round 230v. (PH) 1995, 1996
Hot Spring Classic (F) 1997, 1998, 1999, 2000
Hot Spring Classic (FQ) 1998, 1999, 2000
Hot Spring Grandee (G) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Grandee (GQ) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Prodigy (H) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Prodigy (HQ) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Jetsetter (J) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Jetsetter (JQ) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Landmark (S) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Landmark (SQ) 1997, 1998, 1999, 2000, 2001, 2002
Hot Spring Vanguard (V) 2001, 2002
Hot Spring Vanguard (VQ) 2001, 2002

You may also like…

  • O-Ring, Control Thermistor
    Control Thermostat Thermistor o-ring for the 79006 and 78970 thermistors This o-ring is located on the "inlet" side of the heater and is the larger of the two thermistor o-rings For the outlet side of the heater see the part# 34879 o-ring
    $1.48
    Add to cart