Daikin J3 Fault

[Slim R410a]

Hi Guys,

So I have..(installed myself 2007)

1No. 2MXS50FV1B
2No. FLXS25BAVMB

Customer knows how to use the self diagnosis so called up with a J3 fault.
J3 initially relates to abnormal discharge sensor so I ordered and fitted a new set of thermistors S90. (discharge, ambient air and condenser coil)

J3 faults still persists after 1.5-2 hours operation. Gas weighed out is all there no leaks.

Checked resistances on both indoor units for 1) return air sensor and 2) coil sensor. All 4 ok as per service manual.

Swapped outdoor PCB (borrowed a pcb from a working system with identical outdoor) still J3 after 1-2 hours.

When the system is running there is some cooling effect but no condensation is produced from either of the indoor units. With the gas charge ok this looks like it is something to do with the expansion devices??

[Tayters]

Going out on a limb could it be a head pressure (blocked coil/ambients etc) issue causing discharge temp to rise or units undersized?
Can you measure the pipe temp after the 1.5 hr run to see if it is actually too hot (guess it is if probes and PCB changed...)

If the above is ruled out then I suppose there is too much load for the indoor coil duty (be it a gas or sizing issue) causing the problem. Service valve shut, blocked filter by EEV or EEV as you say. That's me out of ideas.

[install monkey]

lev's on 2mx,4mx multi units are crap- always body sticks- heads ok but pin jammed in shut position- levs mounted on liq line by service valves

[frank]

I would be monitoring the discharge line temperature adjacent to where the sensor is attached to rule out sensor fault.

[passandscore]

What are the operating system pressures?

Does this unit have a heating mode? If so have you ruled out a leaking 4 way valve?

Seeing as both of your indoors units are not producing any cooling, I would venture to guess that the problem is not with the expansion valves. It will most likely be a system problem that is effecting the valves.

- Dirty coils.
- Restricted filters.
- 4 way valve bypassing back into the suction.
- High outdoor ambient temperature.
- High heat load on the indoor units.

Knowing the pressure would be a big help.

[Slim R410a]

Thanks for all the replies.

Both indoor units filters/coil are spotless and free of restriction or dirt as is the outdoor unit.

Air on to the indoors before switching on is 26/27. The outdoor unit sits in the shade after 12 noon. 8.5 to 9 Bar suction pressure for both indoor units.

I am going to rule out under sizing as the system has been fine since 2007. There is also a 2004 FTKS20 wall mounted system in the same property/conditions. (loft conversion 3 bedrooms - 2 have the FLXS25's, 1 has the 20 wall)
After about 10mins of this being on it is 'too cold to stand in front of' and condensation comes pouring out the drain.

I have not taken any temperatures as of yet - as my opening post they do 'work' and cool the room down however don't have that 'bite' of cold air or produce any condensation the drain pans are dry.

The suction flare nuts sweat back but again not as cold as usual.

Spoke to Daikin tech yesterday they said it could not be the eev valve bodies as only the heads fail. (in the past and as IM mentioned above I have had to change the bodies on RXS split outdoor units) But then why would BOTH eev's be faulty??

[install monkey]

get nitrogen on coils - also inspect fan scroll for dust build up- layer of dirt/fluff on return air thermistor?
freeze protect?

[Slim R410a]

I've had both indoor chassis's apart to get the the thermistors can assure you they are spotless even the fan scrolls.

Spoke to Space technical they said it looks like both eev bodies. Going to try swapping the eev heads tomorrow with working ones first.

[joe-ice]

Whats the discharge pressure and temp i feel comparing these to suction pressure and temp could reveal a lot

[Neddy]

Shut the liquid valve and see if the system pumps down to prove the compressor is pumping correctly.
As all ready said measure the discharge temperature. Is the condensor fan running at the correct speed?