Troubleshooting a Mini-split AC Inverter

[natiz]

Hi,

I have a mini-split inverter AC (a WIND INV40A by Tadiran) which stopped cooling a few years ago, and its time I get it fixed.

When the AC starts, the fan starts turning on the outside unit, but then stops after a few seconds. The compressor never kicks in.

The indoor unit then outlines error 06, and the main board (as can be seen in this video) has the led blinking 12 times, indicating E12 which according to the distributor (and google translate) is:

IPM (Driver Board) protection:
1) Check the integrity of the cooling system (and verify the frequency lock).
2) Check the phase voltage between R S T.
3) Check the connection of the capacitor box.

I know my way around a multimeter and I was wondering if I can try finding what the actual issue is before replacing it completely (a new IPM costs more than a new AC for some reason :\)
What do you guys suggest I check?

Attached a wiring diagram by the distributor and a pic of the outside unit boards.

[soldar]

I have had some similar experiences. Unless you have a lot of free time and nothing better to spend it on my guess is that chances are you will waste much time and not get far. From a practical point of view I would suggest finding a pro.

Now, assuming you have time and do not mind wasting it, you need to understand the controller board is not just some basic electronics but a programmed controller.

When it starts up it goes through a routine of checking parameters here and there, waiting for this and that, and it will usually take several minutes before it even tries to start up the compressor. Troubleshooting the board without having complete documentation will be very difficult. You can try all the sensors and other inputs. You might get lucky and find something easy and obvious. Go over all the wiring, connections, etc and make sure everything is as it should be.

I had a unit fail under warranty a couple years ago and the guy came out and replaced both boards (inside and out). He told me the boards are not worth repairing as he, with all his knowledge, could spend hours on each board and only be able to repair a small fraction of them. Not worth it.

A different issue which happens often is refrigerant loss. If the system is not absolutely tight then it might lose some refrigerant. Especially some of the newer refrigerants work at higher pressures and will leak more easily.  A pro has the tools and knowledge that he can check this in a matter of minutes and it is not something that it is worth your time or effort.