Tech Tips: What Causes Evaporator Freeze Up in a Refrigerator?

If you repair refrigeration units, you know that evaporator freeze up is a very common issue in commercial coolers and freezers. However, figuring out why isn't always easy. Fortunately, Heritage Service Group put together a helpful diagnostic list for technicians fixing evaporator coil freeze up in a commercial refrigerator.

Before you begin, remember that you CANNOT just check and resolve one issue and think the job is complete. In many cases, there are multiple issues that simultaneously cause freezing. 

Common Reasons for Evaporator Freeze Up

Below is list of potential issues associated with specific parts and areas in the unit:

Thermostat

• Thermostat is unresponsive intermittently and runs on past its set point.
• Thermostat is INOP and does not shut down power to solenoid.
• Thermostat is set incorrectly (too low) and runs continuously never reaching the set point.

Solenoid

• Solenoid won’t shut down or close even when de-energized.
• Solenoid partially closes but never totally. Unit will generally short cycle because system is constantly equalizing and pressure control energizes condensing unit.

Fan

• Fan(s) are not moving air ( fan bad or wiring short de-energizing fan)
• Fan intermittently dropping out when it runs for a while (check by spinning fans by hand to see if it free-wheels easily or stops short because of bad windings or bushings)
• Fan blade was obstructed and stopped by frost or wires which led to more frost and freezing.

Coil

• Coil airflow was obstructed by debris or plastic.
• Product is stacked too close to coil obstructing airflow.
• Coil fins are badly damaged leading to a small area of freezing which in time grows in size.

Heating Element

• Heating elements (pan and coil) are INOP or not receiving voltage.
• Heating elements (pan and coil) are weak, check recommended amp draw according to factory.

Defrost Timer

• Defrost timer is moving but not energizing elements.
• Defrost timer has been recently adjusted and does not have enough defrost cycles or enough time on each cycle.
• Defrost termination switch is defective.

Delay Switch

• Fan delay switch is defective.

Evaporator Drain Line

• Evaporator drain line is obstructed and water isn’t draining.
• Evaporator drain line heater is not working or de-energized.

Doors

• Doors were left open for an extended period of time.
• Door does not close and make o good seal, gaskets are bad.

Interior Cabin

• Unit was loaded with product that was not frozen to begin with.  Load was too much for unit and moisture content was too high.

Compressor

• Compressor is inefficient and cannot handle what it was designed for therefore running all the time.

Thermal Expansion Valve (TXV)

• TXV is out of adjustment or defective.

Refrigerant

• Unit is low on charge. This cannot be diagnosed until the unit is completely defrosted. (NOTE: This is very unlikely because the unit would have to run quite a while to freeze up and the customer would've noticed the unit was not holding its temperature)

As stated above, the reasons for evaporator freeze up can be one or more of the reasons listed. By thoroughly checking all these potential issues during a service call, you can avoid having a customer call again.

About Heritage Foodservice Group

Are you interested in being featured on techtown? You’re in luck!

We’re currently looking for service companies and technicians just like you to contribute to our website. At the moment, there are two ways you can get featured.

•             As interviewee to be featured on the site

•             Write a guest blog post

Email feedback@techtownforum.com and let us know of your interest. We’ll take it from there.