They have their own specific setup that I can’t remember (too many schematics in my brain). If it runs for a little bit and then shuts off for a while, kicks on for a bit and yada yada, check your condensate line, might be tripping a “safety switch.” Thats a quick fix, vacuum out the line. Check around the condenser and see if there’s a bunch of droppings. Rodents like to keep warm and chew on wires, those little bastards. Could be a number of things. But I’d start with the condy line. Answer from Deleted User on reddit.com
Reddit
reddit.com › r/hvacadvice › [daikin vrv] [220 vac] u4-01 error code help
r/hvacadvice on Reddit: [Daikin VRV] [220 VAC] U4-01 Error Code Help
September 6, 2024 -
My air conditioning failed on me some time today when I was at work, and when I returned home it was 92° inside my home. Figures this would happen during the (hopefully) hottest week of the year in Los Angeles. This system was professionally installed in June of 2020, and has worked without issue until now. The company that did it was bought out by another larger firm, and they are unable to send a tech out for another 17 days. I’m kind of SOL there. I change the filters every six months in the air handlers, and regularly hose down/clean the exterior unit. With a basic visual inspection, it does not appear that there are any blockages/impediments to air flow. I have tried powering off both the exterior unit and both interior air handlers by switching off the breakers on two separate occasions. The cooling works for about 10 minutes and then the error message is displayed again on the interior control panel. Any ideas?
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They have their own specific setup that I can’t remember (too many schematics in my brain). If it runs for a little bit and then shuts off for a while, kicks on for a bit and yada yada, check your condensate line, might be tripping a “safety switch.” Thats a quick fix, vacuum out the line. Check around the condenser and see if there’s a bunch of droppings. Rodents like to keep warm and chew on wires, those little bastards. Could be a number of things. But I’d start with the condy line.
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So the error you're getting is for the loss of communication between the indoor and outdoor unit. Usually you would get this immediately if the communication wire actually has an issue, but since the unit runs and cools for 10 mins that's kind of giving the sign of power loss at the outdoor unit at the 10ish min mark. Sadly I think there is more to your issue than just this error code.
JustAnswer
justanswer.com › hvac › kv8uf-daikin-support-air-con-heater-error-code-u4-01.html
Daikin U4-01 Error Code? Troubleshooting Help & Fix Guide
December 22, 2022 - The U4-01 error on Daikin units typically indicates a temperature sensor or communication fault. First, power off the unit and check sensor wiring connections for looseness or damage.
Waarschuwingscode: U4-00 Daikin. There is communication
Waarschuwingscode: U4-00 Daikin. There is communication problem so he says in de insite unit. Half test ago. Half year More on justanswer.com
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August 24, 2024I have a Daikins inverter that is giving a U4 error code. I
I have a Daikins inverter that is giving a U4 error code. I turned off the power, let stand 5 min, restarted and it More on justanswer.com
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August 3, 2024Daikin Mini Split U4 Error
Work for a Daikin dealer and have to fuck around with these more than I’d like. Have you pulled the charge and weighed it back in to ensure it has the proper charge? I’ve seen multiple strange codes be thrown for a low refrigerant situation. It felt like the unit didn’t know what was going on More on reddit.com
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August 14, 2025[Daikin VRV] [220 VAC] U4-01 Error Code Help
They have their own specific setup that I can’t remember (too many schematics in my brain). If it runs for a little bit and then shuts off for a while, kicks on for a bit and yada yada, check your condensate line, might be tripping a “safety switch.” Thats a quick fix, vacuum out the line. Check around the condenser and see if there’s a bunch of droppings. Rodents like to keep warm and chew on wires, those little bastards. Could be a number of things. But I’d start with the condy line. More on reddit.com
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September 6, 2024Videos
Whirlpool
forums.whirlpool.net.au › home › air con › daikin error code: u1-04
Daikin error code: U1-04 - Air conditioners
Error Code:U1-04 · sounds like you had a phase drop, If the reboot dont work , Could of fried a PCB ? User #101110 3582 posts · bigal99 · Whirlpool Forums Addict · reference: whrl.pl/RdDR4D · posted 2013-Jul-7, 5:43 pm AEST · ref: whrl.pl/RdDR4D · posted 2013-Jul-7, 5:43 pm AEST · d angel writes... We lost power in our house (street? it's been pretty windy) earlier this morning and our Daikin aircon/heating system didn't like it.
Daikin
daikin.com › products › ac › services › error_codes
Error Codes | After Sales Service | Air Conditioning and Refrigeration | Daikin Global
Error Code Search offers information on the cause of the malfunction and the status of your air conditioner by entering the error code.
JustAnswer
justanswer.com › hvac › bvmqb-u4-error-daikin-indoor-unit-keeps.html
Daikin U4 Error Code: Expert Solutions and Fixes
The U4 error on Daikin units often indicates a fan motor or flap actuator malfunction. First, power off and vacuum dust from the indoor unit’s fan and flap mechanisms. Check for obstructions preventing flap movement.
Quality Home Air Care
qualityhomeaircare.com › daikin-thermostat-error-code-u4-01-troubleshooting
Daikin Thermostat Error Code U4-01 Troubleshooting Guide – Quality Home Air Care
The U4-01 code indicates an issue related to communication between the Daikin thermostat and the outdoor unit or a sensor fault within the indoor components. While the exact interpretation can vary by model, the common theme is a disruption in data exchange or measurement accuracy.
JustAnswer
justanswer.com › hvac › c107x-fault-code-u4-u0-two-head-units.html
Daikin Error Code U0-04 & U0: Expert Solutions | JustAnswer HVAC
Fault codes U4 and U0 typically indicate communication errors between the indoor head units and the outdoor condenser. Check wiring connections for loose or damaged cables linking the two head units to the condenser.
Star-supply
star-supply.com › content › Daikin Single- Multi -U4 Error Code.pdf pdf
Daikin Single-Multi U4 Error Codes
Only good for Daikin Single Zones & Multi-Splits-NOT VALID ON VRV OR SKYAIR · U4 Fault code is a Signal Transmission Error (between Indoor Unit and Outdoor Unit)
AirReps
airreps.com › 2025 › 11 › understanding-the-u4-error-code-in-daikin-vrv-systems
Understanding the U4 Error Code in Daikin VRV Systems - AirReps
November 19, 2025 - The U4 error code signals that your Daikin VRV system needs professional attention for a communication problem. While it’s frustrating to see your system shut down, this error code is actually protecting your equipment from operating incorrectly.
JustAnswer
justanswer.com › hvac › pvzz2-waarschuwingscode-u4-00-daikin-communication.html
Daikin U4-00 Warning Code? Expert Troubleshooting Guide
August 24, 2024 - The Daikin U4-00 error code signifies a communication issue between the indoor and outdoor units of your Daikin HVAC system, indicating that the signal between these units has been disrupted or lost.
Airway Group
airway-group.co.uk › home › help & advice › daikin air conditioning fault codes explained [infographic]
Daikin Air Conditioning Fault Codes Explained [Infographic] | Airway
April 2, 2026 - U1 – Reverse phase – The three phase power supply has been reversed. U2 – Open phase or power voltage imbalance – There may be an open phase or a voltage imbalance in the power supply.
HVAC Toolkit
hvactoolkit.org › home › resources › error codes › daikin
Daikin Error Codes - Complete Fault Code List & Solutions | HVAC Toolkit
Complete Daikin error code list for mini-splits, VRV systems, and air conditioners. Find meanings, causes, and troubleshooting solutions for all Daikin fault codes.
ADK Kooling
adk.co.uk › home › air conditioning › daikin error code u4 — vrv communication fault explained
Daikin Error Code U4 | Communication Fault Fix | ADK London
March 23, 2026 - U4 is one of the most common error codes on Daikin VRV and VRF systems. It indicates a communication fault between the indoor and outdoor units. The system can’t operate if the units can’t talk to each other.
Scribd
scribd.com › document › 425197901 › Daikin-error-code-pdf
Daikin VRV Error Code Troubleshooting Guide | PDF | Manufactured Goods | Electrical Engineering
U1 − 01 Reverse phase/open phase for power supply (Master) U1 − 04 Reverse phase for power supply [with power supply turned ON] (Master) U1 − 05 Reverse phase/open phase for power supply (Slave 1) Refer to the “U1” flow chart of each ...
JustAnswer
justanswer.com › hvac › pphzc-daikins-inverter-giving-u4-error-code.html
Daikin Inverter U4 Error Code? Expert Troubleshooting Guide
August 3, 2024 - The U4 error on a Daikin inverter typically indicates a communication or sensor fault. First, power off the unit for 5 minutes to reset. If persistent, check the indoor unit’s PCB connections and wiring harness for loose or damaged cables.
RemoveandReplace.com
removeandreplace.com › home › home air conditioning › daikin air conditioner ac error codes
DAIKIN Air Conditioner AC Error Codes
December 22, 2022 - U0 System Shortage of refrigerant or EEV failure U1 System Negative phase, Open phase U2 System Power supply insufficient U3 System Wiring check operation not executed U3 System Mismatch of indoor and outdoor units – Split only U4 System ...
Reddit
reddit.com › r/hvac › daikin mini split u4 error
r/HVAC on Reddit: Daikin Mini Split U4 Error
August 14, 2025 -
I’ll try to keep this as brief as possible, I’m trying to resolve a U4 code on a single zone RXL09QMVJU, I do not currently have the model handy on the indoor unit. I know the system is old but I’m with one of the few companies in my area that actually repairs things unless a replacement is absolutely necessary.
I’ve been on the phone twice with Daikin tech support, I’ve run through all of the diagnostic procedures they’ve given me so far and even run through others that shouldn’t throw this particular code. At this point both indoor and outdoor boards have been replaced and I’m starting to question if I might have a board that was DOA when I installed it.
Indoor unit turns on, will run on fan mode but any mode that would involve the compressor errors out, I have proper ac voltage to everything, per their procedure Daikin says I should be looking for 53-55v dc at the indoor board from terminal 3 to ground with the communications wire disconnected. I have 75v dc, I also have the sister unit ten feet away in the next room running fine with 75v dc at that indoor board.
Outdoor board sends no voltage to the compressor, fan was ohmed out and fine, emergency cooling runs the indoor unit at full capacity but again outdoor unit doesn’t run at all and I have continuity in the wiring between indoor and outdoor units.
I’ve been getting some inconsistent information from Daikin between the manuals and talking to them so I figured I’d ask here for opinions.
Top answer 1 of 3
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Work for a Daikin dealer and have to fuck around with these more than I’d like. Have you pulled the charge and weighed it back in to ensure it has the proper charge? I’ve seen multiple strange codes be thrown for a low refrigerant situation. It felt like the unit didn’t know what was going on
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Unplug the outdoor fan motor from the board and then start it up. I’ve seen many times a bad outdoor fan cause a U4 code
Daikin
my.daikin.eu › content › dam › DASW › supportavdelningen › Felkoder_SM-TS3errorcode_chart.pdf pdf
Simple Self-Diagnosis by Malfunction Code After Sales Service Division (SM-TS3)
U1 · Reverse phase, open phase · Power supply reverse phase · T phase open phase · Defective outdoor unit PCB (A1P) k k k k k k k · U2 · Malfunction of power supply or · instantaneous power failure · Abnormal power supply voltage · Instantaneous power failure · Defective main circuit ...
Star-supply
star-supply.com › content › Daikin-Troubleshooting Codes.pdf pdf
Trouble Shooting www.climatecenter.co.uk Daikin Trouble Shooting Guide
Capacity setting error · Incorrect ... Codes · Fault Code · Definition · Supposed Causes · Split · Skyair · VRV · Package · HRV · U0 · Shortage of refrigerant · Undercharged, EEV fault, faulty sensor · • · • · • · • · U1 ......
Daikin ONE
daikinone.com › smart_thermostats › oneplus › pros › PhaseTwoErrorCodes.pdf pdf
Climate Talk Fault Code Dealer error code Possible causes Corrective actions
•Call Daikin support at 1-855-DAIKIN1(option 1) •Replace thermostat if needed · Thermostat · Critical · Communication error · 3 · 04 · Thermostat software upgrade error · ClimateTalk firmware was not able to upgrade. •Conduct a warm start of the thermostat.