Daikin NON-inverter monosplit internal unit motor speed accelerates and decelerates.

[pietrafesa]

Dear engineers friend, good morning from southern Italy!
I'm new on this forum, and I approached here since I have an annoying problem with my Daikin FTYN25GXV1B, non-inverter monosplit air conditioner, 7 years old.
That unit has 3 possible speeds: 1 (low), 2 (medium) and 3 (high) and "AUTO" speed.

When I set 3, it runs good, but I don't like speed 3 and speed 2 since the noise.
I have always used speed 1, since it is sufficient for my purpouse.

The problem appeared in summer 2015, when the air conditioner was 6 years old, so very young.
But let me come to problem: when I set fan speed 1 or fan speed 2, independently from the temperature I set, the motor runs continuously accelerating and decelerating, and so on.
It seems to be a "sinusoidal" run, with the minimum speed corresponding to that I have set, and the maximum to speed 2 or 3.
I explain better: if I set speed 1, the motor begin to run with speed 1 but after few seconds he begins to come up to speed 2, and after speed 1 and so on, continuously.

Sometimes it runs normally, at speed I set, but this "normal" run happen only a couple of time per week. Consider I use ir conditioning 3/4 time per day, so I can say that it works bad in 95% cases.

Again, the "sinusoidal" accelerating and decelerating has a period of about 5 or 6 seconds.

I'm little skilled in amateur radio building and electronics repairing, so I can desolder/solder parts with no difficult, but I need your help in order to identify where the problem begins.
Probably in the "voltage regulator" inside the electronics of internal unit board.

Is there anyone here had the same problem in the past?
I probably will change air conditioner if impossible to repair, but I'm sorry, because even if this problem happens, the air conditioning is good, the temperature is good, all the rest is in order and works good.
I appreciate time you would like to spend to help me.

Thank you very much indeed.

P.S.: Same speed problem happens in heating mode, during winter.

Roberto

[vikky1971]

Hi! There, When the air conditioner(AC) is on Auto mode the speed of the evaporator blower(Indoor unit) would change from 1 to 2 or 3 depending on the temperature in the room.
Moreover, instead of changing the whole AC you can renew its power-control card.

[pietrafesa]

Hi dear vikky1971, thank you for answer.
on "Auto" mode I have the same problem.
The power-control card renew costs €200 about, the maintenance service told me, plus €100 manpower.
So, I prefer to spend €600 and buy a new one, inverter.
Do you think something wrong on internal power-control card? Like capacitor, resistor, etc...
Thank you!
R

[vikky1971]

The electronics involved in Inverter AC is too much complicated. First Alternating current is converted to Direct current and then again to Alternating current where frequency is varied to achieve the variable speed of the AC compressor. All achieved through one electronic card.
I am not much familiar with the electronics in the card moreover there is software involved too.
Have you tried resetting the AC from remote control?

[The Viking]

Hi Roberto and welcome to the forum,
Nice to see another ham operator here.

When it comes to your AC unit, the first thing to check is if all the cables and connectors are good, just to make sure that what you are experiencing isn't just due to a dry contact or a damaged cable. It is also worth checking the bearings on each side of the fan scroll (one in the motor and one at the other end). If you checked the above and it haven't solved your problem, then sadly you are looking at spending money.
Unfortunately us AC engineers are generally quite bad at faultfinding on component level, we tend to just replace the circuit boards as a whole.

Spending money on repairs or new unit? Well your unit is 7 years old, spending money on repairs will extend it lifespan with another 3-5 years if you are lucky. On the other hand, if you buy a new system you should be able to get 5-7 years of warranty.
If you do decide to go for a new unit it will by default here in EU be inverter driven but nowadays that is "old"/proven technology and nothing to be afraid of.
Also worth bearing in mind when you select a new unit, don't just look at the cost of purchase and installation, look at the costs of spares as well. How much is a spare compressor? How much for a new indoor PCB? You will be surprised of the differences in spare part prices between different brands. There are also systems on the market nowadays that let you integrate them with your modern interactive lifestyle, make you able to control the via your mobile phone or over the internet.

Just my 2p.

73
M0PKP

:cool:

[pietrafesa]

Thank you people for your kind answers! I appreciate! I will follow your suggestions.
Thank you dear M0PKP! :)
Sincerely,
Roberto.