Sanyo Controller (RCS-SH80AG ) Error 4

[Rtic]

Hi Guys

I'm having some trouble with a Sanyo Air Conditioner (1x Outdoor SPW-CR364GVH56 + 2x Indoor Air Handlers), which controller (RCS-SH80AG) is showing Error 4, is flashing “R C 1 - UNIT 1/2" (it alternates between 1 & 2), and has no system operation. This was a working system up until this error.

A quick look at my little code book indicates error 4 is Comms error. So I’ve inspected the comms wire (from the controller to air handling unit 1 to air handling unit 2) and there is no damage.

At this point I isolated the power completely to the whole system and turned it back on. Now the error disappears and the air handler’s strikes up, but after about 5 minutes the error reappears and the air handlers stop. However, in this 5min period I can set the air handler fan speed, and can hear the fans speed up and slow down, so the controller is successfully sending data.

I have had a look at the outdoor unit, which is switch on, has power and I can’t see no obvious problems. However my attention has been cemented inside, as this error occurs on all settings, including “Fan Only”, so I thought this would indicate that the problem can only be inside; am I right to think this?

At this point I’m tempted to replace the controller, but also have a thought that it might be one of the air handling unit PCBs. When I isolate power to just Air Handler 2, I get the same error after 5 minutes of operation, but this time the error is accompanied with “R C 1 - UNIT 1". When I isolate the power to Air Handler 1 there is no power to the controller at all; but I can’t get my head around this, because the comms wire bridges from Air Handler 1 to Air Handler 2, so should be getting power from Air Handler 2?

Any help is appreciated guys!

JV