N811 • N820 • N821 • N823 • N841 • N842 • N843 • NX811 • NX841 • NXA811 • NXA841

Welcome to our Fridge Defend installation and Norcold N811, N820, N821, N823, N841, N842, N843, NX811, NX841, NXA811, & NXA841 troubleshooting page.

Before reading this page, please click here and view our wiring video.

Click here and view our ARP sensor install video.


Table of Contents

Instructions: Subjects are listed on left. Click the link to the right to go directly to the subject matter on this page.

Norcold N8xx & NX8xx Series Fridge

We have installed the Fridge Defend by ARP on many of these fridges; some are over 16 years old! The installation is very similar to the N6xx refrigerators because the cooling units are just about the same configuration. Thus, we recommend using this page in conjunction with the Norcold N6xx page, please click here .

N811 Cooling Unit

Fridge Defend Location

The photo to the right is a Norcold 811 cooling unit with the Fridge Defend mounted on the factory refrigeration controller cover. The Norcold, N8xx & NXA8xx all have slightly different controllers, but the principles behind the operation and control of the different models is all similar. The fridge in this photo is a Norcold N841.3, where the ‘.3’ indicates that this is a 3-way fridge. Please note that there is a black and yellow pair of wires going to the electric heating elements. One wire pair is for 12VDC heat source and the other is for 120VAC heat source to drive the refrigeration process. Due to the high amperage draw for the 12VDC, most users only run the 12VDC when they are driving, we do not recommend using the 12VDC heaters as they can damage the fridge if your fridge is not protected by the Fridge Defend.

Norcold EZ Install

Wiring Fridge Defend by ARP with Boiler Housing Thermal Switch

The following two drawings show the typical methods of wiring the ARP with the Norcold N8xx series.

The first figure shows the older style wiring scheme. On these refrigerators the power is routed into the boiler housing thermal switch and then to the Norcold control. The Fridge Defend is just wired inline with the power wire to the thermal switch. Power coming from the RV is connected to the ARP red wire, the ARP yellow wire is connected so it sends the power to the Norcold control.

Norcold N611 N811

Wiring Fridge Defend with Boiler Housing New Style Thermal Switch

This next drawing shows the newer style wiring. The boiler thermal switch is wired directly to the Norcold fridge control circuit board. In this case, just remove the 12 Volt power wire from the Norcold control and connect it to the red ARP Control wire. Next, connect the ARP yellow wire to the location on the Norcold control where you removed the power in the earlier step, this will complete the power circuit.

Norcold N811.3 Factory Wiring

Late Model N8xx.3 & NXA8xx.3 3-Way Fridge

This drawing shows how the original wiring is on the Norcold controller (2). Please note the purple wire (the color of your wiring may differ) with the brown arrow. This wire will be removed in the next step.

Norcold N811.3 Factory Wiring

Remove the jumper between terminal 2 and 6 and connect the ARP red wire to terminal-6 and the ARP yellow wire to terminal-2.

ARP Sensor on Boiler

ARP Temperature Sensor

The final photo shows the boiler housing door open, and the boiler sensor of Fridge Defend Control is clipped onto the boiler tube. All versions of the Fridge Defend use the same sensor installation. Please note that insulation is placed between the temperature sensor wires and the boiler tube. This installation is helpful because the temperature sensor cable is isolated from the boiler tube. Do your best to insulate the boiler housing so that heat loss does not affect the cooling efficiency of your fridge. Also, insulate the sensor wire where it passes through the sheet metal boiler housing, the sheet metal will cut the sensor wire and cause the Fridge Defend to display short (SHt) if the wire is not wrapped with some kind of protection.

Fault / Error Codes 811; 820; 821; 841

Please Turn Cell Phone Sideways to see Table

No Display No DC to Fridge Make sure fridge is on.
Check power and ground to fridge.
ARP Control detected an overheat situation, check ARP display to see if a count down period tells when control will turn back on fridge.
dr Door has been open for more than 2 minutes. Close the door.
no FL LP gas burner did not ignite. LP gas turned off.
Low LP pressure.
Click here for pressure test.
Manual shutoff valve is closed on LP solenoid.
no AC No AC voltage to control. Check for shore power at plug.
Check RV circuit breaker, or if equipped, the GFI.
Try RV generator.
Click here for improved AC heater safety.
AC LO Low AC voltage at fridge. Check with DMM to see that AC voltage is in range at fridge.
Click here to check AC heater.
dc LO Low DC voltage at fridge. Check with DMM to see that DC voltage is in range at fridge.
no co The fridge started, but did not cool within 2 hours. If the fridge has an ARP Control, this message should not appear.
Fridge thermistor has failed.
Click here to check thermistor.
Click here to reset 'NO CO' fault.
Temperature number flashes when TEMP SET button is pushed. The refrigerator is operating in Back Up OS mode. The control unit is not getting an input it needs to run.
Fridge thermistor has failed.
Click here to check thermistor.
Check all wiring connections, power down the fridge and then power up.
AC rE Norcold states that "this is a fault within the controls" We assume this is a fault with the AC relay on the Norcold board? We at ARP Control want to help everyone with a Norcold fridge. If a solution to this issue is found please share with us so we can post it to share the joy.
dc rE Norcold states that "this is a fault within the controls" We assume this is a fault with the DC relay circuit? It is possable that this means that the DC relay is stuck? We at ARP Control want to help everyone with a Norcold fridge. If a solution to this issue is found please share with us so we can post it to share the joy.
AC HE Norcold states that "this is a fault within the controls" Fault with the AC Heater circuit.
Click here to check AC heater.
Sr Flame sense circuit failure Turn off fridge and restart.
Check LP Gas pressure and electrode gap.
Click here for gas valve and igniter check.

Flashing LED Error Codes 811; 820; 821; 841

LED Status Gas LED Meaning
OFF OFF Fridge Off or No 12VDC to Fridge
ON OFF 1 Second Intervals Auto Operation, No AC Power or LP Burner failed to ignite
ON OFF once every 3 seconds System is in limp mode
ON OFF once every 3 seconds Mode switch failure
ON OFF 3 times every 3 seconds AC Heater Failure
ON OFF 4 times every 3 seconds Control failure
ON OFF 5 times every 3 seconds No cooling detected
ON OFF 6 times every 3 seconds High Limit Switch Failure, get the Fridge Defend

Norcold 811, 820, 821, 841 Specification Table

Please note that all of the following specifications are believed to be accurate. If any errors are found, please bring them to our attention as soon as possible. For critical specification please contact Norcold as they make changes to their specifications without notice.

Item Value Units
ARP Control Boiler Temperature See Note 1 Below
N6xx Volume 6.3 cu. ft
N8xx Volume 7.5 cu. ft
Off-Level Operating Limit See Note 2 Below
Temp Setting Range 1 - 5 5 = Coldest | See Note 3 Below


Item Value Units
Board 12V Fuse/Heater Fuse 5/30 Amp
120VAC See Note 4 Below Amp

DC Power

Item Value Units
Automatic Ignition 0.5 Amp
Flapper Heater 0.25 Amp
DC Heater N6xx.3 (at 12.0 VDC) 13.79/0.87 Amp at 12.0VDC/Ohms
DC Heater N8xx.3 (at 12.0 VDC) 13.79/0.87 Amp at 12.0VDC/Ohms
ARP Control Fan (25cfm blower type) 0.36 Amp
Total Amp Draw 14.9 Amp

AC Power

Item Value Units
Operating Range 108 - 132 VAC
AC Heater (S/N before 854647) 2.7/41 Amps/Ohms
AC Heater (S/N after 854647) 2.5/48 Amps/Ohms
Measurement Conditions 110/120 VAC

LP Gas

Item Value Units
Gas Pressure 10.5 - 11.5 inch w.c.
Heat Input 1500 BTU/hour
Gas Jet (new style) LP16
Gas Jet (old style) 0.155 Jeweled
Electrode to Burner Gap 1/8" to 3/16" inch


Note 1: 185-195°C - 365-383°F

Note 2: Dependent on ambient and ARP boiler temp.

Note 3: Thermistor Values

Note 4: 8 Amp type AGC fast acting.