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Friedrich Air Conditioner E3 / E4 Error Code

Frost probe open or shorted on Friedrich air conditioners.

FriedrichAll Friedrich air conditioner codes

E3 / E4
May need a pro

The frost probe is a sensor on the cold coil that warns the control when ice is forming. E3 means the probe circuit is open and E4 means it's shorted. The unit keeps cooling, but without the probe it can freeze up.

Compatible models

Friedrich window and wall units from 2008 and 2009: QuietMaster, XStar, and the Premium (KS, KM, SL) and TwinTemp (YS, YM, YL, ES, EM, EL) lines.

Also shown as

These meanings come from Friedrich's 2008-2009 room air conditioner service manual. The Uni-Fit and ZoneAire owner's manuals don't list E3 or E4.

Difficulty

Try the basic checks, but the usual fix is a technician's job.

Not sure you are reading the code right? See how to read Friedrich air conditioner codes.

Safety first: unplug the air conditioner (or switch off its breaker) before touching filters, hoses or panels. If you smell burning or gas, or see water near the outlet, stop and call a professional.

How to fix Friedrich E3 / E4

  1. Watch for icing

    If you see frost on the coil behind the filter, or the airflow drops off, switch the unit to fan-only for an hour so the ice can melt.

  2. Keep the filter clean

    Unplug the unit and wash the filter. Good airflow helps keep the coil from icing while you wait for a repair.

When to call a technician

Book a technician. Friedrich's manual has the probe checked with a meter and either the probe or the control board replaced.

Parts linked to E3 / E4

These are the parts most often behind this code. Tap one to see what it does and the signs it is failing.

Order parts by your full model number so they fit.

Step-by-step guides for this problem

Frequently asked questions

Which Friedrich models show the E3 / E4 code?

Friedrich window and wall units from 2008 and 2009: QuietMaster, XStar, and the Premium (KS, KM, SL) and TwinTemp (YS, YM, YL, ES, EM, EL) lines.

Can I fix Friedrich E3 / E4 myself?

Only the basic checks. You can safely try the steps above, but E3 / E4 usually points to a part or fault that needs a technician.

Other Friedrich air conditioner codes

Last reviewed 2026-10-19. Codes and steps can vary by model; check your owner's manual.

Sources we checked