Fujitsu AOT30PMAL Split Problem

[LeighC]

Hello Gents,
I have the above split A/C reverse cycle & it works fine on heating but the out door unit wont fire up on cooling, it is a R22 model 9 K/W 2.5 ton. There are no fault codes flashing.
Has anyone had this problem please? the unit has not done much work.
Thanks in advance.
Leigh

[Brian_UK]

What do you mean by "wont fire up"?

Doesn't run at all, indoor runs outdoors doesn't?

What is the ambient temperature, thermostat settings?

A few clues to help us along maybe...

[LeighC]

Thanks for your reply, when I select cooling, high fan, 18'C with 32'C Ambient or auto the indoor fan runs about 1/2 speed & the compressor or condenser fan outdoors wont start at all. On all heating modes every thing works fine, suction line to compressor chills off etc condenser fan ramps & nice warm air out of indoor even on a cooler 10'C morning with indoor temp set to 30'C
Cheers - Leigh

[frank]

Check the resistance of the outdoor thermister against the thermister chart. Could be indicating high temp preventing the unit from running

[LeighC]

Thanks, yes I was thinking along those lines, I just have to find it.
Because I was trying to get it to run on cooling to pump it down (I want to relocate the out door unit from front door to back door) I decided to activate the unit in heating mode & disconnect the 4 way valve ( reversing valve) solenoid & it started to cool OK the low side pulled down to 50 psi & I was able to pump it down OK & disconnect & remove the out door unit. The indoor fan ramped right down so I blew air with a large industrial pedestal fan through the evap. I will now work on that out door thermistor.
Can any one tell me where I can find the correct specs for it please, my service manual doesn't delve that deep.
Thanks - Leigh

[LeighC]

Hi again, have done resistance check on out door thermistor CN23 connector & was 14.6K ohms @ 16°C ambient, I only have late 410a manual which is very similar which is 16.1K ohms @ 15°C so don't think this is the problem.
Manual says to check terminal voltage (DC 5.0V) at CN23 at thermistor would this be in referenced to the chassis (GND) or between pins please? with it connected or disconnected?
It says if the voltage does not appear to replace the main PCB.
My manual only says there is only 6 fault codes & only indoor related, later 410a unit has many more, does anyone know how to extract more codes from this earlier R22 unit please?
Thanks - Leigh

[Tayters]

Hi Leigh,

This chart should cover the probe resistances, they seem to have stuck with it through the years.
I've also sent some stuff to your email as they are too big to attach here. Another (older) resistance chart and also a service manual for a similar model. Sometimes our company emails go straight to the trash folder so check there if nothing comes through.
I'm guessing you have a wall mount, inverter outdoor? I think Fujitsu only released 1 type of R22 inverter over here but hopefully it will useful.
Does sound a bit of an odd fault. If the probes read correct then going to be tricky to tell for sure where to go next. Wouldn't have thought the high ambient would hold it off but never say never.
R22 parts over here were discontinued a while back...

Cheers,
Andy.