Mitsubishi Electric MXZ-2C20 to MXZ-5C42 multi-zone outdoor units (NA, NAHZ Hyper-Heat): quick sheet

Covers: Mitsubishi Electric MXZ multi-zone outdoor units covered by service manual OBH702: MXZ-2C20NA2/3/4, MXZ-3C24NA(2/3/4), MXZ-3C30NA(2/3/4), MXZ-4C36NA(2/3/4), MXZ-5C42NA(2/3/4) and the Hyper-Heat MXZ-2C20NAHZ, MXZ-3C24NAHZ, MXZ-3C30NAHZ families. The first digit after MXZ- is the number of indoor ports; the two digits after C are the nominal capacity in kBtu/h. They serve two to five indoor units (wall, floor, ceiling cassette or ducted).

Single sourceBrands: Mitsubishi Electric5 components

The outdoor control board has three LEDs: LED1 (red), LED2 (yellow) and LED3 (green). LED1 and LED2 blink counts identify the fault; LED3 patterns show the status of each indoor unit (A-E) and the result of the automatic piping/wiring line-correcting function. Indoor units also blink their operation lamps when the outdoor unit is abnormal.

Safety first

Power board capacitors stay charged after power off.
No refrigerant charge or LEV body work: refer to an EPA 608 certified technician.

How it works

When the indoor OPERATION INDICATOR blinks at 0.5 s intervals with a beep and the outdoor recall shows outdoor, go to the outdoor LEDs.

Auto line correcting: a switch on the outdoor board starts a routine that detects crossed piping/wiring between ports and corrects the assignment; the LEDs show the result. Hold the switch more than 5 seconds to cancel; previous records are erased when the outdoor control board is replaced.

Discharge temperature protection limits differ by model (for example 222.8 F on MXZ-3C24/3C30/4C36NA versions and 240.8 F on NAHZ and 5C42 versions).

Components & tests

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Two ductless mini-split outdoor units on a house wall, one on a steel wall bracket, with the insulated line set running into the wall by Pedalito, CC0

Diagnostic guides for this appliance

Guide · Air Conditioner

PTAC not cooling (fan runs, air not cold)

Most PTAC no-cool calls are airflow (filter, coils), a wrong control setting or a failed compressor start component. Rule those out before suspecting the sealed system.

6 steps ~60 minmoderate

Guide · Air Conditioner

PTAC not heating (electric heat or heat pump)

PTACs heat with electric strip heat, a heat pump, or both. Heat pump models switch to strip heat in cold weather. Check settings, then the heater element and its limits, then the reversing valve.

5 steps ~60 minmoderate

Guide · Air Conditioner

PTAC error codes: how to read and clear them

Most PTAC brands store fault codes that can be shown with a button combination on the control (for example, on GE Zoneline (2019 technical service guide) you hold FAN and the red AUX button together while the unit is OFF, and AUX clears stored faults; other models use other sequences, so use the model's tech sheet). Read the active code, fix the cause, then clear it.

4 steps ~20 mineasy

Other air conditioners manuals

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Carrier Infinity Greenspeed 24VNA6 air conditioner and 25VNA4 heat pump (variable speed): quick sheet

Carrier Infinity Greenspeed Intelligence variable-speed outdoor units: 24VNA6 air conditioner (up to 26 SEER) and 25VNA4 heat pump (up to 24 SEER, up to 13 HSPF), 2-5 ton. Nomenclature from the service manual: 24 = AC, 25 = HP; V = variable speed; N = Infinity series; A = Puron (R-410A); 6 / 4 = SEER tier; two digits = nominal capacity (e.g. 36 = 36,000 BTU/h); voltage digit 3 = 208/230-1; compressor ID 4 = variable-speed scroll, 5 = variable-speed rotary. Serial format: week + year + plant letter + sequence (e.g. 0118E00001). Other 24VNA families (24VNA0, 24VNA9) use different software and code lists.

5 components4 common failuresCarrier

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Trane XV20i / XV18 variable-speed outdoor units (4TTV0 AC, 4TWV0 heat pump, ComfortLink II): quick sheet

Trane variable-speed TruComfort / ComfortLink II communicating outdoor units: 4TTV0 air conditioners (XV20i family, e.g. 4TTV0024A1000C, 4TTV0036, 4TTV0048, 4TTV0060, 4TTV0061) and 4TWV0 heat pumps (Service Facts 4T-V0-SF). They use an Integrated Variable Speed Control (IVSC) board and a Communicating Display Assembly (CDA) in the outdoor unit. Distributor listings note several 4TTV0 revisions; confirm the full model on the nameplate before ordering parts. Single-stage XR14/XR16 units are on a separate sheet.

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Lennox XC21 air conditioner and XP21 heat pump (Dave Lennox Signature, iComfort-enabled): quick sheet

Lennox XC21 (air conditioner, service literature Corp. 1007-L2) and XP21 (heat pump, Corp. 1031-L7), 2, 3, 4 and 5 ton, R-410A, expansion valve indoor coils only. Both use an A175 main control (outdoor control part number 101798-xx) that works in communicating (iComfort) or conventional 24 V mode, plus a separate fan motor control. The XP21 literature describes a two-stage scroll compressor; the 2018 XC21 literature describes the compressor as one-stage while the same control section covers two-stage units, so confirm staging on the nameplate. For ML14XC1/EL16XC1 single-stage units see the separate sheet.

4 components3 common failuresLennox