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How to repair or reset Code U4 in Daikin mini split Inverter 12,000BTU? Thanks.

I had to disconnect the breaker and remove cables, for doing some repair work on the roof (not related to the AC) when I put them back and turned the breaker ON again, the indoor unit kept flashing. I found out it was code U4. I turned OFF and ON the breaker but nothing changed. I removed both PCB (indoor and outdoor) but could not find any obvious fault. I reinstalled everything back but again nothing changed. Curiously, while playing with the remote control, when going through the error codes, the unit started and began to cool. After about an hour, I stopped the unit to install the covers, etc. When I tried to turn it on again, about two hours later, the U4 Code came back again. The indoor fan unit works when I select the fan mode. Any ideas of what could be wrong? Thanks.

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Posted on Jan 02, 2017

  • 659 Answers

SOURCE: carrier split 42G250HF-1(indoor unit

I'm not sure exactly what unit you have and what controls you have installed on the unit. But....there usually is a flash code schematic on the unit. Usually on the inside of the blower compartment cover. This should tell you what is wrong with the unit. It could have a low voltage short somewhere and is loosing the call for cool. So the answer can be a possible yes to your question but without knowing the flash code, it's hard to tell from my point of view. You might end up calling a service professional out to check it.

Posted on Mar 30, 2009

greenspan
  • 1734 Answers

SOURCE: LG split (3 indoor) LMU360CE

The LED #2 is only flashing while in disconnection or short in Thermistor (3 sec off / 0.5 sec on). If you want to change it, note: this is not an easy job to do! You will need to remove the top panel, then remove the control paneland then the front panel to gain access to the thermistor. The part isnot available to the public and requires an authorized service techfrom LG to take care of this problem. You will need a special tool toremove the front door seal spring clamp.
But you can call customer service @ 800 243 000 and see if theycan transfer you over to parts. Just give them the model and serial #and see if they would be willing to sell you the thermistor part. Youwill also need the door seal spring clamp removal tool to make the jobeasier.

Posted on Aug 02, 2009

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