Fujitsu Split Comms Error E01 faulty AFM?

[online]

Hi,
I'm trying to help a friend repair a Fujitsu AOT45LJBYL inverter split system.
A small lizard has cooked itself on the inverter PCB’s IPM IC and taken it & the compressor out.
They have been replaced by a fridgie, but the unit will not run and still has a communications failure between the ID & OD unit. The fridgie doesn’t know what the problem is. I have managed to find a basic circuit diagram for the unit.

The comms error E01 appears to be caused by an inverter board no power issue. The bridge rectifier is ok (diode check & 240v dc with AFM disconnected), PTC measures around 30-40 ohms cold & looks/smells ok and appears doing it’s job with too much current present at power up (Mulitmeter Peak AC current is 2.4A before its limited) & the issue is possibly a faulty AFM module (assuming the new inverter board is ok). F2 & F4 are still ok on the inverter board. Results from AFM Multimeter checks from post http://www.refrigeration-engineer.co...-General-Fault as per table below measured value column. Diode resistance checks are a bit out of spec, so I checked with diode MM function. If I isolate the AFM from the Inverter board there is 240v DC between P & N (as expected as the filter caps are on the inverter board), but when the inverter board is connected I have 1-2v dc between P&N (not the 340v DC I was expecting probably due to the PTC current limiting). Also tried disconnecting FM1& FM2 & compressor from the inverter board, but no change even if PTC is cool. Looking at the cct diag I should also try disconnecting CN34 to isolate the 4 way valve (haven't tried it yet). Does anybody know if the AFM can be bypassed temporarily for testing (quick 10 second test) to prove whether it’s faulty & causing the PTC to overload? I would disconnect the ACTPM connector & connect W14 to the BR +ve & W15 to the BR –ve.
Thanks for your time.


AFM Testing.jpg

[Tayters]

G'day.

If the ACTPM has voltage only when the main PCB is disconnected then it sound like ACTPM is alright but lets not be hasty. Possibly lizard has fried the fan motor/s and PCB and new PCB is damaged from bad motors, yes, it can get very messy and expensive.

Have you done a diode check of the fan motors?
Have you disconnected all outputs from main PCB (comp and fan motors already like you said but also probes, EEV, HP switch as well) and powered up. 4WV powers from a relay so should be fine to leave in but wont hurt removing it.

Have checked the ACTPM from the table and found working ones not always to the spec although the last two seem more out than you'd expect so yes, possibly there is something wrong with it.
Never tried to bypass the ACTPM and go straight to the main PCB but for a quick test can't see what could go wrong, after all, it is already broken but it looks like you have already proved a fault after the ACTPM anyway.

After all the grief with the fan motors Fujitsu here recommended to change motors, main PCB and ACTPM. Why the ACTPM I asked as it powers up and works. Well the main man said it has happened that it takes a hit and blows later on. This happened to me last year on a MHI unit so just something to bear in mind.

Can send you the circuit diagrams if you need them.

Have found the ACTPM values from the specific manual and they are different. Yes the last two readings seem wrong resistance wise but more sense with the diode readings so, yeah, confusion, can't answer that one.


Thanks,
Andy.

[online]

Thanks for your reply Andy.

My feeling is the AFM is ok even though the last 2 readings are a bit ambiguous (but I wouldn't rule it out yet). The thing I don't like is the AFM has 240V DC at it's output (P&N) if I isolate the Inverter board. I think I might disconnect everything from the AFM board except P&N and see if I can get 320-340v DC on P&N, then check some low voltage rails on the Inverter board after that and the main power relay 12v connector on the Inverter board. If P&N fail to come up then I might look at bypassing the AFM and see what happens.

[online]

Hi,

Just a quick update. I tried removing the inverter board and substituting it with a light globe. I figured the Inverter board PCB was probably only drawing 10w-40w(max) with everything else disconnected and figured it would be a good test for the PTC also. Used a 25W globe initially and the PTC could power the light continuously. Increased it to 50W and the PTC was still ok driving it so I figured the PTC and AFM were probably ok and there was still a fault on the new inverter board. Tried bypassing the AFM and running the inverter PCB direct off the bridge rectifier, but the PTC was once again overloaded. I believed the new inverter PCB had been damaged by installing it with a fault still on the system. After leaving site, the owner got a Fujitsu tech out who diagnosed 2 faulty condenser fans & a faulty inverter board. I went back later & checked the condenser fans. The 15v rail on pin 5 was shorted to the fan ground on pin 4 on both condenser fans. I put the inverter board on the bench and found the chopper transistor in the SMPS section was shorted along with a few other components. A working inverter board & 2 compressor fans got the unit back up and running. Thanks for your help.