MRCOOL air conditioner E5 error code: indoor coil temperature sensor fault

What the E5 code means

E5 on a MRCOOL air handler means the evaporator coil temperature sensor (T2) has an open or short circuit. Gen 4 and Gen 5 units show it as EH 61. The sensor tells the unit how cold the indoor coil is, so the unit stops when the reading is lost.

The T2 sensor clips into the middle of the indoor coil. The board uses it to stop the coil icing in cooling and to manage the fan in heating. Without a sensible reading, the unit cannot run safely.

Code meanings differ by display. On the indoor unit of every generation, E5 or EH 61 is the coil sensor. On the outdoor display of a Gen 1 to 3 multi-zone unit, E5 is a voltage fault instead.

Common causes

Listed from most to least common.

1. Coil temperature sensor failed (open or short circuit)
2. Sensor plug loose on the indoor control board
3. Sensor wire frayed, corroded or damaged
4. Dirty or blocked indoor coil affecting the reading
5. Indoor control board fault

How to fix the E5 code

Unplug the air conditioner or switch it off at the breaker before removing any panel or filter.

1. 1

   Step 1: Power cycle the unit

   Turn off the breaker for at least 15 minutes, then turn it back on and watch for the code.

2. 2

   Step 2: Clean the filters

   Lift the front panel, slide out the filters and rinse them in lukewarm water. Let them dry fully before putting them back.

3. 3

   Step 3: Check the sensor plug

   If you are comfortable removing the air handler cover with the power off, check that the sensor wire is firmly plugged into the board and is not frayed or corroded. MRCOOL's own guide includes this step.

4. 4

   Step 4: Book a repair if it returns

   If E5 comes back, the sensor likely needs replacing. MRCOOL sells replacement sensors for its DIY series.

You'll need: Screwdriver, flashlight, multimeter (optional).

How to reset the MRCOOL air conditioner

1. Turn the mini-split off with the remote.
2. Switch off the breaker for the system and the outdoor disconnect switch. MRCOOL suggests leaving the power off for 15 minutes so the boards fully reset.
3. Restore power and turn the unit back on. The compressor normally waits about 3 minutes before starting, so give it time before judging.
4. If the same code comes back straight away, the fault is still there. Work through the fix steps above, or call a technician.

Parts that may need replacing

Check your model number on the label inside the door or on the back before ordering.

• MRCOOL indoor coil temperature sensorCheck prices

When to call a technician

If E5 returns and you do not want to open the air handler, a technician can test the sensor with a meter and replace it. If the sensor tests fine, the indoor board is the next suspect.

A typical repair for this code costs $150–$400 in the US, including parts and labor. Prices vary by area and model.

Models this applies to

• DIY Series ductless mini-splits (Gen 1 to 5), single-zone and multi-zone
• Advantage Series mini-splits
• Olympus Series mini-splits
• EZ-PRO mini-splits

Codes can differ slightly between models. Your owner's manual is the final word and is available from MRCOOL support.

Frequently asked questions