On Daikin RZR-TA and RZQ-TA SkyAir systems, AJ is an indoor unit error code meaning "Defective capacity setting" (service manual SiUS281811EA). The indoor unit PCB reads its capacity from the resistance of a capacity setting adaptor and from its own IC memory, and sets AJ when the capacity code is not saved and no adaptor is connected, or when a capacity that does not exist for that unit is set. Daikin lists only two causes: a defective capacity setting adaptor connection and a defective indoor unit PCB. If the indoor PCB was replaced with a spare and no adaptor was installed, the manual's fix is to install a capacity setting adaptor.
What does Daikin AJ mean?
SiUS281811EA covers RZR18-48TAVJU (cooling only) and RZQ18-48TAVJU (heat pump) outdoor units with FCQ, FHQ, FAQ, FBQ and FTQ indoor units. Its error code table and sub-code table list:
| Code | Daikin's description | Diagnosis as printed |
|---|---|---|
| AJ (indoor unit) | "Defective capacity setting" | Operation lamp blinks; listed on p. 208 with a pointer to section 4.18 (p. 237) |
| AJ-01 | "Capacity setting error" | "There is an error in the capacity setting of the indoor unit PCB." (p. 210) |
| AJ-02 | "Electronic expansion valve setting error" | "There is a fault in the setting of the gear type electronic expansion valve/direct acting type electronic expansion valve." (p. 210) |
The sub-codes appear when a navigation remote controller (BRC1E series) is in use. On the BRC1E73, a blinking green operation lamp means "The system stops operating", and pressing the Menu/OK button shows the error code (p. 205). AJ-02 is a valve setting fault, not a capacity adaptor fault; the manual gives no separate procedure for it.
How does the indoor unit decide it is an AJ?
Section 4.18, "Defective Capacity Setting" (p. 237):
| Item | As printed in SiUS281811EA |
|---|---|
| Method of error detection | "Capacity is determined according to resistance of the capacity setting adaptor and the memory inside the IC memory on the indoor unit PCB, and whether the value is normal or abnormal is determined." |
| Error decision conditions | "The capacity code is not saved to the PCB, and the capacity setting adaptor is not connected." "A capacity that does not exist for that unit is set." |
| Supposed causes | "Defective capacity setting adaptor connection"; "Defective indoor unit PCB" |
How do you fix a Daikin AJ error?
The AJ flowchart (p. 237) has two questions. Power off before connecting or disconnecting connectors.
- Was the indoor unit PCB replaced with a spare PCB? If not, "Replace the indoor unit control PCB (A1P)."
- Was the capacity setting adaptor installed when replacing the PCB? If not, "Install a capacity setting adaptor." If it was, "Replace the indoor unit control PCB (A1P)."
Our practical advice, not Daikin's wording: AJ that appears right after a board swap points first at the adaptor. Before removing an old board, note whether a capacity setting adaptor is plugged into it and the marking on it, and compare it with the replacement board's instructions.
Does the outdoor unit need a capacity setting adaptor?
On some sizes, yes. Section 2.1 "Capacity Setting" (p. 169) is a field setting on the outdoor unit, separate from the indoor AJ check. It carries a caution: "Be sure to carry out capacity setting after changing the main PCB (A1P) to spare PCB. (for RZR30/36/42/48TAVJU and RZQ30/36/42/48TAVJU only)". The instruction is "Attach the capacity setting adaptor corresponding to capacity class to connector X51A." and "Capacity setting is not required for RZR18/24TAVJU and RZQ18/24TAVJU."
| Outdoor model | Adaptor type (as printed) | Connector |
|---|---|---|
| RZR30/36/42/48TAVJU, RZQ30/36/42/48TAVJU | J56 | X51A on main PCB (A1P) |
| RZR18/24TAVJU, RZQ18/24TAVJU | Capacity setting not required | None |
That is the only capacity setting adaptor table we found in the manual. It gives an adaptor type, "J56", not an orderable part number, and we found no table of indoor unit adaptors.
The AJ section covers the indoor unit PCB and its adaptor only. A missed outdoor setting is listed elsewhere: the manual's UA section, "Improper Combination of Indoor and Outdoor Units, Indoor Units and Remote Controller" (p. 285), lists "Setting of outdoor main PCB was not conducted after replacing to spare PCB." as a cause. Daikin's general SM-TS3 list has the same idea in a UA row: "Setting of outdoor unit PCB was not carried out after replacing to spare PCB". See our Daikin U4 transmission fault article, which also covers the RESET (BS5) step the manual requires after an indoor or outdoor PCB is changed (section 3.7, p. 193).
Where else does the capacity setting cause trouble?
- C6-01 "Defective combination of indoor unit PCB and the fan PCB": "Check whether the capacity setting adaptor is correct and the type of the fan PCB is correct." (p. 210). Section 4.22 (p. 242), for FBQ-P units, lists "Defective connection of capacity setting adaptor" and asks "Was the correct capacity setting adaptor installed when replacing it with a spare PCB?"
- High and low pressure checks. Both fault trees (CHECK 1 and CHECK 2, pp. 292-293) include "Defective main PCB (Including capacity setting)" with the question "If a spare PCB is installed, is the capacity setting properly made?" See our Daikin E3 and E4 article.
Parts involved
| Component | Role in this issue | Where to find it |
|---|---|---|
| Capacity setting adaptor | A missing adaptor after a spare PCB is fitted is the AJ fix in the flowchart; the outdoor 30 to 48 sizes also need one at X51A. These listings are titled "Capacity Setting Adaptor". SiUS281811EA prints no adaptor part numbers, so the titles do not tell you which capacity class or model each fits; match by the part number for your unit. |
065336J — Capacity Setting Adaptor 065331J — Capacity Setting Adaptor 066965J — Capacity Setting Adaptor |
| Indoor unit control PCB (A1P) | A listed cause of AJ, and the flowchart's answer when no spare PCB was fitted or the adaptor is already in place. Match by the part number on the board. | Daikin Parts for VRV Units |
Scope: This article covers the AJ code, the AJ-01 and AJ-02 sub-codes, the outdoor capacity setting and the related UA and C6 entries as printed in Daikin service manual SiUS281811EA for RZR18-48TAVJU(A) and RZQ18-48TAVJU(A) SkyAir outdoor units and the indoor units it lists. Other Daikin product lines may use AJ or capacity settings differently. The adaptor listings are examples by live product title, not a fit confirmation for any capacity class or model.
Before you order
Read the indoor and outdoor model numbers from the nameplates and the part number on the existing board and adaptor. For related codes, see our Daikin U4 article and our Daikin L5 and E9 article, or browse Daikin Parts for VRV Units. To confirm which adaptor your unit takes, contact us at help@totalhvacparts.com or 302-219-4994 with the model numbers, the board part number and the error code.
Frequently Asked Questions
What does AJ mean on a Daikin remote?
On RZR-TA and RZQ-TA SkyAir systems, AJ is an indoor unit code for "Defective capacity setting" (SiUS281811EA). The indoor PCB could not get a valid capacity from its capacity setting adaptor or its memory, or a capacity that does not exist for that unit is set.
Why does my Daikin show AJ after replacing the indoor board?
The manual's AJ flowchart asks whether the indoor PCB was replaced with a spare and whether the capacity setting adaptor was installed when replacing it. If the adaptor was not installed, the fix is "Install a capacity setting adaptor."
What is AJ-01 versus AJ-02 on a Daikin?
AJ-01 is "Capacity setting error", an error in the capacity setting of the indoor unit PCB. AJ-02 is "Electronic expansion valve setting error", a fault in the setting of the gear type or direct acting type electronic expansion valve. Sub-codes show on BRC1E series remotes.
Does a Daikin RZQ outdoor board need a capacity setting adaptor?
For RZR30/36/42/48TAVJU and RZQ30/36/42/48TAVJU, yes: after changing the main PCB (A1P) to a spare, attach the adaptor for the capacity class to connector X51A (adaptor type J56 in the manual's table). The 18 and 24 sizes do not need a capacity setting.
Sources
- Daikin Service Manual, RZR-TA and RZQ-TA Series, SiUS281811EA (model list p. 11; capacity setting p. 169; section 3.7 p. 193; BRC1E73 display p. 205; error codes p. 208; sub-codes p. 210; AJ section 4.18 p. 237; C6 section 4.22 p. 242; UA section 4.54 p. 285; CHECK 1 and CHECK 2 pp. 292-293)
- Daikin Global, Simple Self-Diagnosis by Malfunction Code, SM-TS3 (pages 1-6, list of error codes) (UA row, spare PCB setting cause)
- Live product titles for the parts listed above, as shown on each product page
Daikin air conditioning systems involve line voltage, high-voltage DC on inverter boards, pressurized refrigerant and rotating equipment. Service should be performed only by qualified personnel, following the manufacturer's service manual for your model and your facility's lockout/tagout procedures.