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  1. #1
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    Fujitsu split error help


    Hi there. I have a Fujitsu AST12LSACW/AOT12LSAC heatpump that has an issue. When I turn it on and put it into, say, heating mode the operation light stays lit and the timer light starts flashing 1 second on 1 second off. The outdoor unit does nothing although it is getting power and the interconnecting wiring is correct. I can hear the indoor 'click' to signal the outdoor but this is when the timer light starts to flash. I suspect it is some sort of signal error but as I dont have a manual I cant be sure. Any help would be greatly appreciated.



  2. #2
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    Re: Fujitsu split error help

    Flashing lights indicate comms error. If you press the test button you can get a bit more detail.

    Operation should flash quick the 2 or 3 flashes of timer mean indoor unit can't see outdoor. 4 or 5 flashes mean outdoor can't see the indoor.
    Health and safety first..........unless I'm in a hurry.

  3. #3
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    Re: Fujitsu split error help

    Hey thanks Tayters. The timer flashes 2 times. I have checked the outdoor pcb's with no obvious burn outs or fuses blown and the signal cable has no breaks. Am I correct in thinking its probably stuffed?

  4. #4
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    Re: Fujitsu split error help

    Possibly but there are a few outdoor PCB's to diagnose.

    First off I'd see if there was comms voltage (50-100V AC between neutral and terminal 3). Sounds like indoor board livens the relay up so fair chance no outdoor livening up. If there is comms voltage then strange but you'd have to diagnose the comms is corrupted due to poor cabling/terminals or faulty controller outdoors or if you are unlucky indoors.

    If no comms voltage then try this approach:

    Check the fuse on the outdoor unit then follow the route the power takes.

    It goes from the fuse to the controller PCB on W1 and W2.
    Out on W6 and W5 to the diode bridge.
    Out of the diode bridge as 340V DC on the red and black wires to the ACTPM.
    Out of ACTPM (still 340V DC) on yellow and blue to the capacitor then back to the controller PCB on the white and purple wires (terminals TM1 and TM2.

    TM1 goes to a 15A fuse F1 (also check the smaller 3.15A fuse)on the controller PCB then out to Transistor PCB
    TM2 is the neutral line and pops out at W15 to Transistor PCB.

    If there is no mains AC voltage between W5 and W6 Search 'Posistor' on the site to explain more although bear in mind you don't have the fancy fan motor so you will need to follow the diagram for checking that one. You will need to power down for a couple of minutes. Unplug components the main voltage follows, power back up and see if you get voltage. If you do, it's a case of powering down for 2 minutes, plug in the next component and power back up. Follow this until you find the component which is causing the posistor to go open circuit.

    I'll send a diagram of the circuit to your email.

    Hope that helps.

    Cheers,
    Andy.
    Health and safety first..........unless I'm in a hurry.

  5. #5
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    Re: Fujitsu split error help

    hi a ast12 should still be under warranty ring fujitsu agent and get them to sent someone round

  6. #6
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    Re: Fujitsu split error help

    So I tested the comms with multimeter and seems ok (fluctuating but was around 55-60v). W1 had 240v and W2 nothing when to earth but 240v across them. W5 and W6 nothing at all and therefore nothing any further on. On the main PCB a little black box at W10 and W11 gets warm though but I cant find it on the wiring diagram. I unplugged everything off the main pcb and turned the power on (Dont know if thats good for it) bu still nothing and the error lights on the indoor still point to comms error from the outdoor.

  7. #7
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    Re: Fujitsu split error help

    Quote Originally Posted by beatnik View Post
    So I tested the comms with multimeter and seems ok (fluctuating but was around 55-60v). W1 had 240v and W2 nothing when to earth but 240v across them. W5 and W6 nothing at all and therefore nothing any further on. On the main PCB a little black box at W10 and W11 gets warm though but I cant find it on the wiring diagram. I unplugged everything off the main pcb and turned the power on (Dont know if thats good for it) bu still nothing and the error lights on the indoor still point to comms error from the outdoor.
    hei tayters, i was browsing around and saw u trying to help this guy out aswell.. hope you dont mind i try....
    correct me if am wrong or giving out unnecessary steps..

    allright beatnik:
    I have seen some fujitsu models do that, Im also not very sure bout the heat pump models but i reckon there are pretty much the same ..just a reverse cycle ...

    1. turn off from mains, then start up again - hit test run from remote and hear the click ( outdoor terminal should receive the supple from indoor) if so try step 2.

    2. for the small unit, 12000btu like your, try checking the indoor pcb - makesure fuses are good.

    3. check indoor pipe thermistor and outdoor discharge thermistor (i know it aint relevant, but i have seen units give out this error signals when after trying/diagnosin for hours we found it was d thermistor thats faulty)



    Im not an expert, but some of these hav thought me a thing or two during my troubleshooting....

  8. #8
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    Re: Fujitsu split error help

    Quote Originally Posted by beatnik View Post
    So I tested the comms with multimeter and seems ok (fluctuating but was around 55-60v). W1 had 240v and W2 nothing when to earth but 240v across them. W5 and W6 nothing at all and therefore nothing any further on. On the main PCB a little black box at W10 and W11 gets warm though but I cant find it on the wiring diagram. I unplugged everything off the main pcb and turned the power on (Dont know if thats good for it) bu still nothing and the error lights on the indoor still point to comms error from the outdoor.
    If you just had W5 and W6 disconnected, when the system was powered up then there should be 240V AC between them. If not then it looks like the controller PCB is goosed.
    It's a fairly straight forward circuit between power in and power out on that PCB. The 240V goes in, darts off to a reversing valve relay, fan motor and an IC (from memory) then through a thermal fuse (posistor in Fujitsu language) to W5 (or W6, the other is the neutral line).

    I can't see W10/11 either. But then I can't find the butter in the fridge when it's staring me in the face! Think it harkens back to a caveman thing - focusing on ones prey whilst the female knack of peripheral vision is due to their nesting instinct protecting the young. You heard right ladies - I'm a born hunter gatherer!


    Quote Originally Posted by rashVRF View Post
    hei tayters, i was browsing around and saw u trying to help this guy out aswell.. hope you dont mind i try....
    correct me if am wrong or giving out unnecessary steps..

    ...

    Im not an expert, but some of these hav thought me a thing or two during my troubleshooting....
    I'm no expert either so the more the merrier mate. Can't say I've seen a thermistor fault causing a comms error but sometimes with a PCB, who knows what's going on in there. LG's are a favourite for playing up because of dodgy thermistors but no or odd fault codes. Nothing like an LG to keep the mind active.

    Cheers,
    Andy.
    Health and safety first..........unless I'm in a hurry.

  9. #9
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    Re: Fujitsu split error help

    Quote Originally Posted by Tayters View Post
    If you just had W5 and W6 disconnected, when the system was powered up then there should be 240V AC between them. If not then it looks like the controller PCB is goosed.
    It's a fairly straight forward circuit between power in and power out on that PCB. The 240V goes in, darts off to a reversing valve relay, fan motor and an IC (from memory) then through a thermal fuse (posistor in Fujitsu language) to W5 (or W6, the other is the neutral line).

    I can't see W10/11 either. But then I can't find the butter in the fridge when it's staring me in the face! Think it harkens back to a caveman thing - focusing on ones prey whilst the female knack of peripheral vision is due to their nesting instinct protecting the young. You heard right ladies - I'm a born hunter gatherer!




    I'm no expert either so the more the merrier mate. Can't say I've seen a thermistor fault causing a comms error but sometimes with a PCB, who knows what's going on in there. LG's are a favourite for playing up because of dodgy thermistors but no or odd fault codes. Nothing like an LG to keep the mind active.

    Cheers,
    Andy.
    lol... lets us know wat happen beatnik...

  10. #10
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    Re: Fujitsu split error help

    Ok, so I tested the thermistors and they were fine. All fuses indoor and out are also fine. There was a suggestion that it could be under warranty still but the user and service manuals are dated 2003/04 so I best not risk getting someone out here to find that I have to pay. I am reasonably sure its a PCB fault and who knows how much they cost now. Anyway I have a spare old aot12rsgc system and since its only a sleepout that its in I have swapped systems and now have a nice warm room. Thanks to everyone who helped out but it looked like a dead end for me so I to the easy road.

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