23rd Oct 2026
How to Test an RV Refrigerator AC Heating Element (Ohms Chart for Norcold and Dometic)
HOW-TO · ELECTRIC
How to Test an RV Refrigerator AC Heating Element (Ohms Chart for Norcold and Dometic)
Cools on propane but not on 120V? The heating element is the first thing to test. Here’s how, with the manufacturer resistance specs.
The short version
- Unplug the fridge, disconnect the element’s two leads from the board, and measure ohms across them at room temperature.
- Compare with the spec. Dometic allows ±10%. Open (OL) or way out of range = replace the element.
- In range but still no electric cooling? Norcold’s flowcharts point to the power board; on Dometic, check the 5 A AC fuse and the lower board.
- No spec for your element? Use Dometic’s formula: ohms = volts × volts ÷ watts, with the volts and watts stamped on the element.
Before you start
- You’ll need a multimeter that reads ohms, a screwdriver and a flashlight.
- Unplug everything disconnect 120V and 12V. Norcold points out the fridge draws power from more than one source.
- Let it cool test at room temperature. A hot element reads higher.
- Access the element sits in a tube (heater well) on the back of the cooling unit, under the insulation, behind the lower outside vent. Its leads run to the power board.
Covers these models
Absorption refrigerators that run on 120V and propane (and 12V on 3-way models).
What you’ll see
- Cools on propane, not on 120V. The classic sign.
- Norcold codes: “AC HE” on the 1200/1210, 2118 and N6/N8 means the AC heater circuit is open. N7X/N8X flashing once means an AC heater fault. See 1200 AC HE, 2118 AC HE, N6/N8 AC HE and N7/N8 1 flash.
- Dometic: no AC operation while gas works. See Dometic not cooling on AC.
Step-by-step: test the heating element
STEP 1
Check that 120V is getting to the fridge
Plug something into the fridge outlet or measure it. Norcold wants 108–132 VAC; Dometic lists 100–132 V. Also check the fridge’s AC fuse on the board: 5 A on the Norcold 1200 and Dometic, 8 A on the Norcold 2118 and N7/N8.
Power present and fuse good?
Fix the power first
Reset the breaker or GFCI, or replace the fuse. Dometic says to find out why a fuse blew before replacing it. A shorted element can blow it, so still test the element.
STEP 2
Disconnect the element leads
Unplug the fridge again. Find the two heater leads where they connect to the power board (Dometic: terminals J7/J8 on the lower board) and disconnect them. Norcold 1200 and 2118 models have two heaters; test each one.
STEP 3
Measure resistance across the two leads
Set the meter to ohms and touch one probe to each lead. Compare with the table below.
Reading within spec?
Replace the element
OL (open) means the element has burned out. A reading near 0 Ω on a 120V element means it’s shorted. Either way, replace it with the same wattage. Dometic: “Never over or under size the AC heater.”
Element is good: look at the board
Norcold’s flowcharts (1200, 2118, N7/N8) say to replace the power board when the heater reads in range. Dometic: if 120V reaches the board but not the heater terminals J7/J8, replace the lower board. Reconnect the leads firmly first: a loose terminal causes the same symptoms.
STEP 4
Optional: check for a short to ground
With the leads still disconnected, measure from each lead to the metal sheath of the element or the cooling unit frame. It should read open (no continuity). Any reading means the element is shorted to ground. This is standard electrical practice; Norcold and Dometic don’t publish a ground test.
Manufacturer resistance specs (120V AC heaters)
| Model | Heater | Spec (room temp) |
|---|---|---|
| Norcold 1200 / 1210 | 2 × 225 W | 58–68 Ω each |
| Norcold 2118 | 2 × 300 W | 45–51 Ω each |
| Norcold N7 / N8 Polar | 1 × 300 W | 45.7–50.5 Ω (spec page); flowchart says 38–50 Ω |
| Norcold N600 / N800 (older N6/N8) | 300 W | 40.3 Ω ±5% (rated at 110 V) |
| Dometic RM2652, RM2662/63, RM2852, RM2862 | 325 W | 44 Ω ±10% |
| Dometic RM3762 / RM3962 | 325 W | 44 Ω ±10% |
| Dometic RM2351–2354, RM2451–2454, RM2551–2554 | 175 W | 80 Ω ±10% |
| Dometic RM2612 / RM2812 | 295 W / 325 W | 48 Ω / 44 Ω |
From Norcold and Dometic service manuals. Norcold 2117: no published spec found; use the formula below with the wattage stamped on your element.
No spec for yours? Calculate it
Dometic’s method: volts × volts ÷ watts = ohms, and a good element reads within 10% of that. Use the voltage stamped on the element. Some older elements are rated at 110 V or 115 V, which changes the answer: a 300 W element rated at 110 V works out to 40.3 Ω, not 48 Ω.
| Stamped rating | Calculated ohms | About ±10% |
|---|---|---|
| 175 W @ 120 V | 82.3 Ω | 74–91 Ω |
| 225 W @ 120 V | 64.0 Ω | 58–70 Ω |
| 300 W @ 120 V | 48.0 Ω | 43–53 Ω |
| 325 W @ 120 V | 44.3 Ω | 40–49 Ω |
| 420 W @ 120 V | 34.3 Ω | 31–38 Ω |
| 300 W @ 110 V | 40.3 Ω | 36–44 Ω |
Calculated by us from the formula, not manufacturer specs. Where the manufacturer publishes a spec (table above), use theirs.
Testing the 12V heater on 3-way models
The same method works, but 12V elements read under 1 Ω, so use a good meter on its lowest range and subtract the reading you get with the probes touching each other. Examples: Norcold N7LX / N8LX 0.81–0.91 Ω (service manual flowchart) and Norcold N600 / N800 3-way 0.87 Ω. Dometic’s example: a 200 W, 12 V element is 0.72 Ω. Dometic protects the 12V heater with a 30 A fuse. On Norcold N6/N8 3-way models, “dc HE” means the DC heater failed (dc HE flowchart).
12V heaters
Match the part number on your old element.
Parts for this repair
Norcold AC Heater 638374 (Polar N7 / N8 / N10, newer N6XX / N8XX)View part →
Norcold AC Heating Element 618872 (1200 / 1210)View part →
Norcold AC Heating Element 630807 / 638372 (1200 / 1210)View part →
Norcold AC Heating Element 637136 (2118)View part →
Norcold AC Heating Element 638369 (2117)View part →
Norcold AC Heating Element 630811 (many post-2006 models)View part →
Norcold AC Heating Element 621702 (many older models)View part →
Dometic AC Heating Element 3313107.039View part →
Dometic AC Heating Element 3850644414 (RM2620)View part →
Dometic Heater Element 3850644620 (RM1350 / NDA1402)View part →Shop by category: Norcold AC heaters, Dometic heating elements. Match the part number or wattage on your old element, or ask us with your model and serial number.
FAQ
How many ohms should an RV fridge heating element read?
It depends on the wattage. Common values: Dometic 325 W = 44 Ω, Norcold N7/N8 300 W = about 46–50 Ω, Norcold 2118 = 45–51 Ω per heater, Norcold 1200 = 58–68 Ω per heater. Otherwise use volts × volts ÷ watts.
What does OL mean when testing the element?
Open circuit: the element has burned out and needs replacing.
The element tests good but the fridge still won’t cool on electric. Now what?
Check the AC fuse and the leads’ connections, then the power board. Norcold’s flowcharts say to replace the power board when the heater reads in range.
Can I use a higher-wattage element to cool faster?
No. Dometic says never to over- or under-size the AC heater. Use the wattage your model calls for.
Still stuck? Ask a tech with your model, serial number and what you’ve found. We’ll confirm the part before you order.
Specs and procedures from Norcold (1200, 2118, N7/N8, N600/N800) and Dometic (Americana, RM3762/RM3962, Service Tips 81, manual-control service manual) service manuals. Calculated values are labeled.