Need help diagnosing serial communication error with Fujitsu Halycon mini-split

Illinois_Sam

Indoor unit ASU18RLXS
Outdoor unit AOU18RLXS

I don't know the age but it was here when I bought the house 10 years ago. It has worked fine until recently.

Symptoms: No heating or cooling, but the fan in the inside unit does blow. The outside unit never fires up.
The orange Timer LED on the inside wall unit blinks orange twice every 12 seconds. On the remote wired thermostat, a yellow LED, next to the orange ON/OFF button blinks continuously.
The thermostat error code 1 seems to point to a serial communication error.

There are no Fujitsu dealers nearby. Closest is maybe 45 miles away. I called a big HVAC contractor in our area and he looked at it for 45 minutes, then said he would get back to me. Never did. Two days later I called his office and no return call, so they don't want to work on it. I'm sure they would be happy to sell me a new system though.

I have been unable to find diagnostics for this exact unit, though some model numbers seem close.

Checkpoint 3:
The input voltage to the outside unit is 235 VAC.

Checkpoint 4:
The three wires that go from the outdoor unit to the indoor unit read:
Red to Wh 0 VAC
Blk to Wh 235 VAC steady
Red to Blk 120 - 205 VAC

However, when those wires come to the inside unit, the black and red wires seem to be reversed. I assume there is a splice somewhere in the line and they got switched.

I saw the other thread with a similar, unfortunately I can't find any similar fuses in my unit. There are two glass fuses soldered to the main PCB and on the power board. I really scrutinized them and they all seem to be okay.

The outdoor fan motor turns freely when I spin it by hand. There is a red LED soldered to the main PCB, but I've never seen it light up. I don't know if that means anything.

So folks, any suggestions? Further questions for me? It seems like things point to the main PCB. I found one on Ebay, but it didn't quite match up and one of the connectors was different. I see AliExpress has one but I thought I'd check with you kind folks and see if I am something missing here.

The part number is K07BS-C-A (04) and there is another number 9707656015.
The AliExpress number is K07BS - C - (04) 9707656015 A, very slightly different. Their photo of the board is a little blurry and I see that a couple of connectors on their board are white, while they are pink on the current board on my outside unit. Don't know if that means anything or not.

pecmsg

Splicing is not allowed on the communication wiring.
Run a new 3 wire between the indoor and outdoor unit and see if the issue goes away. If it does than a new wire is needed, if not than a contractor is needed.

Illinois_Sam

pecmsg said:

Splicing is not allowed on the communication wiring.
Run a new 3 wire between the indoor and outdoor unit and see if the issue goes away. If it does than a new wire is needed, if not than a contractor is needed.

Thanks. I can chase that down tomorrow, it is a long run from our up stairs, through the garage attic, etc.

But still, after at least 10 years, what changed?

pecmsg

If there’s a splice ?

Jamie Hall

I really don't like the voltages you quoted. Like... really don't like them. Unless someone screwed up the colour coding -- which is possible, but not likely if it was professionally done -- both red and black to white should be around 110 to 120 VAC, and red to black should be 220 to 240 VAC. All those voltages should be rock solid. Check all your power supply wiring, right back to the main breakers.While you are at it, check the ground as well.

Illinois_Sam

Jamie Hall said:

I really don't like the voltages you quoted. Like... really don't like them. Unless someone screwed up the colour coding -- which is possible, but not likely if it was professionally done -- both red and black to white should be around 110 to 120 VAC, and red to black should be 220 to 240 VAC. All those voltages should be rock solid. Check all your power supply wiring, right back to the main breakers.While you are at it, check the ground as well.

These numbers seem to jive with the Fujitsu trouble shooting. There are the voltages between the outdoor and indoor units. They say the voltages should swing between 90VAC and 270VAC. I have no idea why they want this. Checkpoint is the input terminals to the outdoor unit. Checkpoint 4 Checks the serial signal, what ever than means. They also don't describe what is abnormal.

Jamie Hall

Hmm. Well, let's go back to square one here. Find the AC input wires at the unit -- wherever they are. There may be three (red, black and green or bare) or four (red, black, white, green or bare). At the AC input, red to black may, as Fujitsu suggests, be between 187 and 254, but should be absolutely stable. If your house has 110/220 wiring, which is much more common, red to black should not be less than 198, nor more than 242.

Now check the voltage to ground -- bare or green. Both red and black should be within 5 volts of half of whatever you measured between red and black. If there is a white wire, measure from rad and black to white. Each should be within 2 volts of half the value between red and black.

Any other result indicates a serious wiring problem -- not necessarily in the same circuit as the unit. If you are not up to troubleshooting this, please get a licensed electrician to make certain that all your neturals and grounds are intact.

The serial communication line does fluctuate, and the only way to determine whether it is correct or even close to correct is with an oscilloscope. Voltage measurements are almost useless.

Illinois_Sam

Here are the power leads at the outdoor unit. L1&L2 are the supply power, from the house circuit breaker, and show 233VAC from the white lead to the black wire. White to ground is 116VAC, as is the black to ground.


Leads 1, 2& 3 go to the indoor unit, and the colors do correspond from the outside to the inside.
Red to White 233VAC
Red to ground 116VAC
White to ground 116VAC
Red to Black 234VAC
White to black Varies approx. 38VAC to 150VAC
Black to ground. Varies approx. 0VAC 10 115VAC

Jamie Hall

Please go back to your main switch panel. If you are not comfortable opining it and taking measurements, get an electrician to do so. There will be two power feeds to the main breaker and one neutral to a busbar. There will also be a ground to a different busbar.

Now. Each power feed should read 110 to 120 volts to both the neutral busbar and to the ground busbar. The voltage between the two power feeds should be 220 to 240 volts. The voltage from the neutral busbar to ground should be very small -- certainly ness than 10 volts.

If this is not the case, find out what is wrong with the wiring.

Now. Coming from the circuit breaker in the panel to your main power feed poiint in your unit, you shiould have red, black, white, and ground.. What bothers me is that you appear to have white and black on the power feed block (and a ground). A white wire may be used instead of red or black, provided it is clearly and permanently labeled -- which yours isn't. Trace that back to the units breaker on the main panel, and make sure that the white wire in the cable is connected correctly to a hot, not to a neutral,

ratio

The indoor unit is fed with 240 volts via terminals 1&2, communications is via a voltage superimposed on the third wire—referenced to one leg of the 240 volts. The white wire is not a neutral (it should probably have been taped with a different color). While you can't actually validate the communications without a 'scope, a varying voltage inside the limits they give means it's probably ok.

My first guess is a failed control board, followed by a failing indoor feeder. Maybe pull the wires off & check them to see if they're grounded, although I would expect that to blow a fuse if it were happening.

pecmsg

Fujitsu wants stranded wire not solid. 

tim smith

True on comm over 1 of the legs. Been a long time since I installed the 1st halcyon multi split on the west coast, think it might have been 1st in US if memory serves me. Was a steep learning curve at the time. It was working well after 10 yrs or so but then the waterfront house went through major remodel/addition. I have done mostly mitsubishi over the years since.