Fujitsu AOT36LMADL

[m00t]

Hi There,

I have Fujitsu AOT36LMADL (outdoor unit model num that is currently displaying e0:01 on the wall control panel. The unit is approx 6 years old.

Not sure when this started, it could have been when we were away on holiday or sometime after we got back.

In any case I pulled the case off the outdoor unit and noticed that the F2 fuse was gone. I replaced the F2, this was to no avail, I also think that with the F2 pulled the control board is getting power (DC??) where as with F2 replaced there is no power at the control board. Further to this when I took the case off a saw a dead gecko around the diode bridge. With the help of my father in-law (electronics engineer), we did some dead and live testing, noting that there was no DC coming out of the diode bridge (however diode bridge tested OK with diode check function of MM). Tracing where the voltage was lost, if turns out that the posistor is knocking out the 240v as it comes in. Further looking on this forum this suggests that there is a short either in the fan motor (im going to check tonight with diode check) or the compressor (dont have the tools to megger the compressor). Long story short, my father in-law said it would be most beneficial if we had a detailed circuit diagram (as opposed to the block plan on the underside of the lid of the outdoor unit) to work with. Is anyone able to provide this? Also I would be grateful if anyone can point me where to look further from here.

Thanks

[Tayters]

Sent to your email fruity.

[m00t]

Further update on the above.

I used my multimeter in diode test mode, to test the fan motor. Red(MM) to Red and Black(MM) to Black gives 0.054v and Red(MM) to Black and Black(MM) to Red 0.054v. Additionally testing the black and white connections gives similar results Red(MM) to White and Black(MM) to Black gives 0.091v and Red(MM) to Black and Black (MM) to white gives 0.091v. From my reading this is bad?? (for the record the fan casing is metal). However leaving the fans unplugged and turning the unit on there is still no AC getting to the diode bridge (i.e. the posistor is still kicking in). What would be the next thing to disconnect / where to from here?

Thanks,

[m00t]

Just a quick update. With the fans unplugged the same error was present, so disconnected everything from the control board, still no AC at the diode bridge. The only way I could get AC to the diode bridge and DC out was disconnecting the power supply to the control board.

So my question is, what is next? I am hesitant to replace the control board without further testing at risk of damaging the new board, especially given the potential bad result posted above from the fan motor?

Any help would be much appreciated.

Thanks,

[leegally1983]

Just a quick update. With the fans unplugged the same error was present, so disconnected everything from the control board, still no AC at the diode bridge. The only way I could get AC to the diode bridge and DC out was disconnecting the power supply to the control board.

So my question is, what is next? I am hesitant to replace the control board without further testing at risk of damaging the new board, especially given the potential bad result posted above from the fan motor?

Any help would be much appreciated.

Thanks,


send me your email and i will send you a circuit diagram

[Tayters]

Ah, that motor testing is if you have a brushless DC type. Your type is a bog standard PSC jobbie (4 wires, not 6).

To confirm best follow the route of the circuit and plug it in as you go until the posistor goes open, then you have plugged in a faulty part. Not sure what power supply you have disconnected so to take it from the top (I guess you might have sussed some of this out anyway..)

Circuit route is:

240V into power supply PCB, +ve then goes out to posistor then back into PCB to diode bridge, 340V(ish) DC comes out to TM102, TM103 to ACTPM (this improves power factor, take out noise etc) on red and black and out of ACTPM on white and violet back into power supply PCB. In the power supply PCB it goes 2 ways, on TM107, TM110 to transistor PCB to power inverter module and also to W25, W27 to provide DC to controller PCB.

Once everything has power and if all is good the posistor will handle the low current and when ready for action relay K101 on the power supply PCB will close (effectivley shorting the posistor) and more current can pass.

To confirm what is making the posistor go open in the first place I would start the circuit from the beginning and plug in as you go and monitor when the diode bridge loses voltage. If you narrow it down to a PCB then it's time to unplug stuff off that board it to see if it is a faulty component causing grief.

In your case I think then with the DC supply (W25, W27, is that what you mean by power supply to control board?) plugged in then posistor open but closed when unplugged shows so a faulty controller PCB or something faulty plugged into it. Follow F2 on the schematic it looks like it provides power to the transistor board through a load of small transformers and the low voltage supplies for the unit (5, 12 18 and 24 V) and also it looks like it goes to the transistor PCB so you can see it can get a bit messy when checking.

If you find the PCB to be faulty you still may not have proven why it failed in the first place as it may be a component which did it. Check other parts as best you can - probes read high resistance, EEV 45ohms between red/orange, red/white, brown/blue, brown/yellow, inverter module I did a checking thing for it - search for inverter testing and it should crop up and finally no wires shorting to earth. Only thing you can't test (although I always stand to be corrected!) is the circuit on the different PCB's. Careful when unplugging any high voltage DC. Best power down for a few mins until charge has dissipated or the high voltage can spark across and that really will damage stuff.

Always worth giving the PCB's the once over to look for any obvious scorching. Looks like the zapped geko didn't cause this damage as the diode bridge seems to be working.

Hope that makes a bit of sense, it's been a while since I've got this stuck in so might be a bit rusty in places but should give your tinkering some help.

Happy testing!
Andy.

[ozairman]

Gecko's, Lizards, Frogs love the back of the control PCB on these models, especially around the switchmode power supply transformer on the control board if that has been shorted out it will cause the posistor to open when it is connected. Also when checking the EEV coil and sensors make sure you check resistance to the chassis of the machine, the low voltage DC floats at about 80-90 V to the chassis and if there is a short there it will also cause the posistor to open.