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MRCOOL / DIY 5th Generation

PC 44 error code

Outdoor zero-speed protection assigned by the manual to the current overload diagnostic.

Severity
technician
Verified
Jul 18, 2026

What triggers it

Outdoor zero-speed protection assigned by the manual to the current overload diagnostic.

What to do

  1. Check whether protection was activated in standby; if so, replace the outdoor main PCB.
  2. Check power voltage, outdoor terminal voltage, L/N voltage, and current; restart when supply returns to normal or reconnect wiring where needed.
  3. Measure P-N voltage where applicable and check reactor wiring and function.
  4. Replace the reactor if the reactor or inductance is not functioning normally.
  5. Check outdoor ambient temperature, outdoor ventilation, outdoor fan, dirty heat exchanger, system pressure, and refrigerant system; clean, ventilate, repair fan issue, replace outdoor main board, or recycle overcharged refrigerant as directed.

Which systems show it

  • MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.

Related codes

Technician scope

Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3

Source

MRCOOL R454B DIY-5 service manual
Document
data/sources/mrcool-diy5-service.pdf
Section
4.3 Error Display; 4.7 TS08-S
Page
37, 67
Verified Jul 2026

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