Daikin RY125KY1 - Only one fan spinning.

[deron]

Hello All,

I have just moved into a house and have an odd issue with my Daikin RY125KY1 unit (assuming 15-20 years old) where one of the fans isnt spinning on the unit.

If I turn it on in cool mode, both fans will turn on medium/high for about 3-4 minutes then after this, the top one will turn off leaving the bottom running only.

If I turn it on in heat mode, only the bottom fan will turn on eventually causing the top half of the coil/condensor to freeze up and then causing it to go into defrost mode.

I have had a A/C technician come out to assess the unit, he checked the gas and fan capactitors and then switched the wiring for the two fans which cause the other one to run ruling out a bad motor.

He concluded that the fan relays must be bad (tapped them to see if a sticking relay was an issue with no difference) and as there are no spare parts available, recommended me to quote me on a complete new system.

The main board of this unit is a RY100.125F (EC9540(C)).

The unit otherwise works fine, albeit likely at a reduced capacity due to one fan spinning.

In an attempt to research this myself, I noticed various posts on the forum where thermistors can cause a fan to spin down or related to an attempt to lower head pressure. There is also mention that this may be a feature of that unit as mentioned in


https://www.refrigeration-engineer.c...9-daikin-ry125

The RY series outdoor units was manufactured in Japan to be matched with a Japanese indoor however in Australia the indoor units were manufactured in Sydney to suite Australia conditions and larger homes. They therefore have a slightly larger coil than the Japanese one. You will find that on start-up that the outdoor fans will be delayed from starting by up to 5mins. This was due to the unit not wanting to raise the HP to rapidly in heating mode with the Japanese indoor. This is not so much of a concern with the Australian indoor.

You will also find that when the outdoor fan starts that only one operates. Can't remember which (top or bottom) but this was again not wanting the HP to raise rapidly or too high. This also creates issues with frequent defrost due to high RH is the air especially is temperatures above 0deg C.

I checked the thermistors in a off state and got the following which appears to be fine

Approx 20degree celcius day.
R1T (Air) - 22.51 kΩ (20 deg C)
R2T (Coil) - 31.29 kΩ (15 deg C)
R3T (Discharge pipe) - 218.7 kΩ (22 deg C)

Would be grateful if anyone could shed some light on this issue before forking out for a new unit. The unit doesnt display any error codes or shutdown completely