---
title: "How to Test a Refrigerator Thermistor — With the Maker’s Own Number"
description: "How to test refrigerator thermistor with multimeter: testing a refrigerator thermistor with a multimeter: the ice-water method, U-Line's own published…"
url: "https://ulinemiami.support/blog/how-to-test-a-refrigerator-thermistor/"
date_modified: "2026-08-29"
Category: "Troubleshooting"
---


# How to Test a Refrigerator Thermistor — With the Maker’s Own Number

## How to test refrigerator thermistor with multimeter: why this test is the first one on a U-Line

Most makes tell you when a sensor has failed. This one does not — and what it does instead is the single most useful thing to know about the appliance.

From U-Line's own service manual: if a zone thermistor fails, the unit **continues to cool in a backup mode — Self Preservation Mode — to preserve the integrity of the contents**, and otherwise operates normally. On the 2000 Series that backup is a fixed cycle, ten minutes on and forty minutes off, whatever the cabinet actually needs.

So the appliance does not stop. It does not beep. It does not put anything on the display. It runs, it lights up, it answers every button, and it never quite gets where you set it. The complaint that arrives is *"it runs all the time and it still isn't cold enough"*, and on a bad day that gets quoted as a sealed system.

A thermistor is an inexpensive part. A sealed system is not. That is the whole reason this page exists.

## The number, and why it is worth having

A thermistor is a resistor whose value changes with temperature, so "is it good" is meaningless without "at what temperature". Fix the temperature and the question becomes answerable.

**U-Line publishes the figure: about 16.1k ohms in an ice-water bath, plus or minus five percent.** Its own manual gives it in the same paragraph as the warning about connections. Very few makers print this, and it is the difference between a measurement and an opinion.

## Doing it properly

**Isolate first.** At the breaker if the unit is built in, because you are not going to reach the plug. Everything below assumes the appliance is dead.

**Make a real ice bath.** Ice and water in a cup, stirred, left a couple of minutes. A cup of ice with no water in it is not at freezing point and neither is cold tap water; both will give you a number that means nothing.

**Unplug the sensor from the harness and read across its two pins.** Multimeter on resistance, autoranging or set to the 20k–200k region. Give the tip time in the bath before you read — thirty seconds is not enough, two minutes is.

**Compare.** Within five percent of 16.1k: the sensor works. Open circuit: the sensor or its lead has broken — that is what the control logs as E1, E2 or E3. Dead short or a wildly low reading: E5, E6 or E7. Far off but not open or shorted: it has drifted, which is the one the appliance hides best.

## The half that gets skipped

A sensor that tests good and a cabinet that is still wrong is not a dead end. It is a pointer at the **connection**.

U-Line applies dielectric grease to every thermistor connection during manufacture, and its manual says why: a connection that has corroded changes the resistance values on their way through to the board. In practice that means a perfectly good sensor can be reporting a temperature that is several degrees out because of a dull green contact behind a panel.

So the connector gets looked at, cleaned, and re-greased rather than reconnected as found. A repair that puts a new sensor into a corroded connector fails the same way in a season.

## Which sensor, and how to know before you start

The error log names them, and reading it first saves testing three to find one:

| Logged | What it is |
| --- | --- |
| E1 / E5 | Thermistor 1 — the cabinet sensor, reading the compartment |
| E2 / E6 | Thermistor 2 — the evaporator sensor, which defrost timing is set by |
| E3 / E7 | Thermistor 3 — multi-zone and combination cabinets only |

The odd fact worth knowing: on a single-zone cabinet, U-Line's own service menu writes *"does not apply to this model"* against E3 and E7. The same number means a real problem on one U-Line and nothing at all on another.

## When to stop and call somebody

- **If the reading is fine and the cabinet still is not.** The next steps are in the service menu — sensor offsets, defrost parameters, the model number the board is programmed to — and that is a different kind of work.- **If you cannot reach the sensor.** The evaporator sensor lives behind a panel inside the cabinet, and on an undercounter unit that is a genuinely awkward space.- **If more than one sensor tests badly.** That is rarely three failed sensors. It is usually one thing upstream of all of them.

Whatever you find, write the readings down. A technician arriving to *"I measured 16.4k in ice water and the cabinet still sits four degrees warm"* starts a long way ahead of one arriving to *"it isn't cold"*.

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