20 Most Recent Fujitsu 18R1 Air Conditioner - Page 9 Questions & Answers

Serial signal reverse error. Basically the outdoor unit is not talking to the indoor unit. This is normally due to damage to the outdoor controller PCB and it needs to be replaced.

As stated, sounds like a reversing valve issue, likely need a technician. What exactly happens when in heating? Does it run, still cold, just warm not hot??? If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

the heating function feeds power to the reversing valve to enable heating the valve coil should be electrically tested, pos opened circuit (burn out )

That's no easy chore to achieve! My friend from another HVAC company changed 1, said he'd never do it again. He had to pull the unit from the wall. But if you try it, most of these units are snapped together by plastic tabs. I've tried to pull 1 to clean the blower wheel. I have 15yrs exp. in the field, 2 yr associates degree, been pulling wrenches since I was a kid, and I will not change that style of blower wheel. I usually ask the customer to change the unit. I know this won't help your situation but it's my opinion from experience.

Without any knowledge or tools your only attempt could be pulling the disconnect for 10 seconds and reinserting. If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

Try changing the batteries and if that doesn't work then call the manufacturer for a replacement. If you need more questions for your AC Repair needs, check us out online.

Change batteries in remote.

Check error code is correct as this extremely rare. Possible fan motor fault instead. If error code is correct, replace indoor controller pcb.

From the service manual: Serial forward transfer error during the operation When the outdoor unit does not receive the signal for 10 consecutive seconds during the operation > Outdoor unit stops. [Diagnosis Point] Check the indoor /outdoor cable connection (in order). If the cable wiring is not abnormal, measure the voltage of the outdoor unit terminals and diagnose the defective location. (Refer to the after mentioned [Serial Signal Diagnosis] for the voltage measuring method and diagnosis method.)

This is an "outdoor temperature thermistor open/short" error. An easy and cheap fix but you will have to buy the part from Fujitsu.

The red light (operation) flashing 5 times can be one of four things depending on the green light (timer) but the green light should flash at the same rate as the red light, not faster - either 2,3,5 or 6 times. Anything other than these is abnormal and you will need a tech to diagnose. Could be a faulty controller board or compressor.

Is this unit battery powered?