Had a frustrating time figuring this out but this may help others. On 210 volt mini splits L1 and ground also carry the serial communications between the units. This is also true on 230v units, however there you have L1 and L2 plus ground. Only L1 carries the comm. If you use the same color wire for L1 and L2 it is easy to inadvertently connect the wire from L1 on the outdoor unit to L2 on the indoor unit, and if you do this, the units cannot communicate. Simply swap the wires at L1 and L2 on either unit, but not both. As soon as I did this the error disappeared and the unit functioned perfectly. Next time I will not use black wire for both L1 and L2 (which otherwise is standard practice normally). Instead I will use black for L1 and red for L2. Then I will know that L1 on the outdoor unit is connected to L1 on the indoor unit.
This requirement for L1 ou to connect to L1 iu is nowhere in the Fujitsu trouble shooting manuals, but speaking to a Fujitsu tech, he casually mentioned this as he was telling me a series of complex trouble shooting techniques. I wrote down all these other tests, but I tried this first for a quick fix of a vexing problem.
Paul
This requirement for L1 ou to connect to L1 iu is nowhere in the Fujitsu trouble shooting manuals, but speaking to a Fujitsu tech, he casually mentioned this as he was telling me a series of complex trouble shooting techniques. I wrote down all these other tests, but I tried this first for a quick fix of a vexing problem.
Paul
