Norcold High Temperature Sensor (HTS)

Part Numbers 637360 & 634677

Limit Switch (recall switch) -- All About

The Norcold recall will disable your refrigerator after the cooling unit has failed, or the device fails1. While the Fridge Defend will prevent most cooling unit damage from occurring in the first place. In the event of an unpreventable cooling unit breach, the Fridge Defend will react at a much lower temperature than the Norcold High Temperature Sensor (HTS) device, thus significantly lessening the chance of fire 2.

See this video and the companion videos below, you decide for yourself what is safe.

By Norcold's words, the Norcold High Temperature Sensor (HTS)3 device will not prevent fridge failure (click here to read letter from Norcold to Fridge Defend). It could be that a letter from Norcold may not be totally convincing, nor the fact that Norcold attempted, unsuccessfully, to get a patent (click here for Norcold's application). This video should be the 3rd and final convincing factor, seeing is believing!

Default4 Fridge Defend Set-Point ~217°C (422°F) - Boiler Steel Strongest
Norcold HTS Set-Point @ 62°F ~600°C (1112°F) - Boiler Steel Not Safe
Video Length: 2:28 (minutes:seconds)
Actual Test Length: 5:27
Sample Rate 1 second
Red Hot Test Curve

QUESTION: If Norcold states in an NHTSA document "the steel material can soften and rupture", how do you feel about the red hot metal in this test? click here to read letter from Norcold to NHTSA

SCIENCE: "The steel structure of the World Trade Center would not have to melt in order for the buildings to lose their structural integrity. Steel can be soft at 538°C (1,000°F) well below the burning temperature of jet fuel." click on this link to read more about this quote.

Why & How We Performed the Test

First the why, ever since we have been producing the ARP/Fridge Defend control, it has been reported that Norcold states that the Recall, or High Temperature Monitor does the same thing as the Fridge Defend. First, the Fridge Defend is patented, therefore it cannot preform the same task in the same way. Second, Norcold sent us a letter stating that their High Temperature Monitor does not protect the fridge from leaks, click here to read the letter.  Clearly Norcold's statement are in conflict with the letter to us, and the test results, which clearly demonstrate this fact.

Below is the plot of the Norcold High Temperature Monitor seen in the video. We show what the normal boiler temperature of the fridge is ( green zone ). We show the temperatures that the Fridge Defend turns off the fridge to help prevent damage to the boiler ( yellow zone ). And then the temperatures at which damage will occur to the boiler ( red zone ). Damage to the boiler leads to failures of the fridge, and in turn fires. The top of the ( red zone ) is 600°C (1112°F), the temperature at which the Norcold High Temperature Monitor turned off the fridge in this test. The blue line/curve (diagonal line) in the plot is data from the tests on the Norcold circuit combined with the real time tests shown in the video above. The dots on the plot are the measured temperature from the video test, the temperature values for the dots are read on the right of the plot.

Norcold Recall Test Curve

Sensor and Instrument Calibration

The Fridge Defend works on a simple, yet complex to understand principle that is used commonly to calibrate temperature monitoring test instruments. This physical law is called phase change.

Simply put, phase change is the phenomena where substances hold a constant temperature while changing phase from one state to another at a fixed pressure. In this context the term "state" means the physical state of the substance, solid, liquid, or gas. Water is used to calibrate instruments as seen in this video. The Fridge Defend uses the phase change temperature in the cooling unit to determine that the boiler is at a safe temperature.

Red hot steel, as seen in the video above is also used to determine temperature. Thus, the tests are confirm for accurate temperature by the equipment used combined with the known physical properties for states of the measurements.

NHTSA Recall Campaign 08E-030, 09E-026, 09E-027, & 10E-049

Norcold models listed in tables below from years 1999-2001 add thermal switch kit on replacement cooling units. Then, 1996-2010 NHTSA campaign 10E-049 mount thermocouple (seen in test video) to identify overheat situations sooner than the thermal switch could and shut the system down before a fire can manifest (Norcold stated to the NHTSA, but fires continue to be reported). For fridge after the year 2010, the thermal switch is standard equipment.

Norcold 1200 Series RV Fridge Dates & Serial Numbers

Model Affected Manufacture Date Serial Numbers
1200 Series January 1, 2002 to January 31, 2005 999032 to 1449595
1200; 1210 Models February 1, 2005 to October 1, 2012 8000101 to 16310278

Norcold 1200 & 1210 Models That Have Boiler Failure Leading to Fire

1200 1200LRIMSSD 1210ACIMD
1200AC 1200LRIMWH 1210ACIMSS
1200ACIMBK 1200LRWH 1210IMBK
1200LR 1201LRIMSSD 1210IMSSD
1200LRBK 1201LRIMWH 1210ACSS
1200LRIM 1201LRIMWPM 1210SS
1200LRIMBK 1210 1211IM
1200LRIMBKD 1210AC 1211IMSS
1200LRIMD 1210ACIM 1211IMWPM

Norcold 2118 Models That Have Boiler Failure Leading to Fire

2118 2118SS 2118BK
2118IM 2118IMSS 2118IMBK
2118IMD 2118SSIMD 2118IMDBK


1) Failure rate of the HTS, "why are they not doing something to improve that one part that fails on a regular basis?".

2) Although the Fridge Defend is designed to prevent damage to your refrigerator, when installed and maintained properly, the Fridge Defend will prevent the boiler temperature from ever reaching the high temperature that would trigger the Norcold device. We do not recommend the removal of the Norcold device.

3) Norcold Refrigerator Cooling Unit Temperature Monitor Control 637360 kit started its life as an NHTSA recall for the Norcold 1200, 1201, 1210 & 1211 refrigerators as a result of fire issues.  It came as standard equipment on fridges such as the 1210 & 2118 after the year 2010. For the refrigerators that were recalled, please click here for offical Recall Notice "no cost to you".

4) We use the term "Default Fridge Defend Set-Point" simply because the Fridge Defend can be tuned for either a Dometic, Norcold, or Amish cooling unit fridge. This will change the temperature that the Fridge Defend turns off a particular fridge heat source.