Fujitsu Defrost frequency

[IanS]

Fujitsu - General AS18-NR Split system

Hi, This is my first post on this forum because this is the first time I have ever owned an Air conditioning system. I am a Brit now living in Sydney and have purchased a property with two systems. The ducted system upstairs runs fine but the smaller split system downstairs keeps on going to defrost.

It is winter here so I am running as a heater and every 5 minutes it stops heating and starts the defrost cycle. (indicator light comes on) pumps out a small amount if cold air then 4 minutes later whooshing sound and it bursts back into life as a heater again. It is between 10 & 15 degrees Centigrade outside so its not really cold. The outside heat exchanger is definitely not freezing up but as an experiment I disconnected the heat exchanger temperature sensor in the outside unit and this improved the situation so that its now 13 minutes on and 4 minutes off.

I don't have a manual but all air filters are and heat exchangers are clean. There doesn't seem to be much else I can maintain.

Any body want to suggest what might be the cause? What would be the effect if I was short on gas?

thanks in anticipation
Ian

[IanS]

forgot to say it is a reverse cycle sysytem but hopefully this was obvious!

[sinewave]

It shouldn't be going on to defrost at all at a 10-15 degree ambient temp outside.

Could be a faulty sensor fooling the PCB board or a faulty board etc etc.

Either way it's not a DIY fix so I'd just ring a local A/C firm to take a look.

[icecube51]

wat is the manifold saying, is the pressure good in cooling and in heating ??? do you have a stable reading or is it floating fort and back??

see the manifold furst, can be water in the system.

good luck, Ice

[Brian_UK]

What is the manifold saying, is the pressure good in cooling and in heating ??? do you have a stable reading or is it floating forth and back??

see the manifold first, can be water in the system.

good luck, Ice

It is unlikely that water in the system is going to cause this sort of effect and the poster probably does not have any means of checking the pressures.

Please consider your answers before jumping in.

[IanS]

Absolutely right Brian_UK I don't have pressure checking facilities.

As I said in my opening post I have tried disconnecting the sensor on the outside unit in the hope that this was faulty but although initially it seemed to make a difference it seems to have reverted back to 5 minutes heat and 4 minutes Defrost so I have reconnected it.

As I said I am a novice when it comes to aircon. What are the typical symptoms of low gas?

[nike123]

Absolutely right Brian_UK I don't have pressure checking facilities.

As I said in my opening post I have tried disconnecting the sensor on the outside unit in the hope that this was faulty but although initially it seemed to make a difference it seems to have reverted back to 5 minutes heat and 4 minutes Defrost so I have reconnected it.

As I said I am a novice when it comes to aircon. What are the typical symptoms of low gas?

If sensor is OK and outdoor unit airflow is OK, then your symptoms are for low gas charge or restriction.
First you need someone to check sensor and air flow, then, if that is OK, to recover and weight refrigerant.
If refrigerant amount is OK you have restriction, and if amount is low, you have leak.
Then service engineer should find leak, repair, pressure test and evacuate moisture and non-condensables. Then refrigerant should be charged by weight.