AC PCB

Repairing another Air Conditioner Unit

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Intro

I did a post some time back about repairing a portable air conditioner unit. They’re not very complex bits of kit and, unless the compressor has broken, they’re usually very easy and cheap to repair.

Following the 2 days of apocalyptic summer the UK had to endure in July 2022, I went looking for another portable AC unit to keep my office cool whilst working from home during the summer days. And I found a stonker! A broken AirForce GPCN12A5NK3BA, for only £20. It’s a 12,000 BTU unit with a huuuge fan that might blow the roof off, if you’re not careful 😀

AirForce GPCN12A5NK3BA

Opening it Up

This unit is remarkably simple to open up. It has 2 “security” type screws on the top that you need a fork shaped screwdriver to open and then two Phillips screws on the bottom. The front panel then lifts up and slides off. The front panel has a motorised louvre vent which you simply need to unplug two connectors from to fully detach it.

The PCB can be exposed by removing the 4 screws from the metal cover with the circuit diagram on it.

I could also see that the heatsink on the back was clogged full of dust. Removing the back was slightly more involved but it was just a case of removing a multitude of screws and lifting the cover off. It can be easily cleaned with a soft tooth brush, very careful vacuuming with a brush attachment, and a fin comb if you’re feeling fancy.

Diagnostics

When I got the unit and plugged it in, the top display turned on but none of the fans nor the compressor turned on. It was feasible that all 3 of the large capacitors which helped these things start up had died… but it felt unlikely. I tested each of the capacitors and found that only one of them was dead. This turned out to be the capacitor which powered the fan which blows cold air out into the room. Upon removing this capacitor, it was clear that it had dramatically blown as it had leaked a sort of molten plastic:

This capacitor was removed and a new one ordered but, given the others were OK, it clearly wasn’t the primary issue.

Next, I just followed the voltage on the PCB:

There was 240v coming into the connector block at the top of the unit so the next point to check was the two fuses you can see (covered in a yellow plastic shroud) at the bottom of the PCB. This is where I lucked out. As I poked the fuses with my multimeter, to establish the voltage, the unit beeped at me. It quickly became clear that the fuse holder contacts were dirty and weren’t making proper connection with the fuses. I removed the fuses, cleaned the contacts with a toothbrush and some Isoproyl, then put the fuses back in.

The unit now powered up, the compressor and exhaust fan ran ok. The top fan ran, slowly, if I gave it a prod. Once the new capacitor had been installed, the top fan ran perfectly on its own.

Venting Hot Air

On this unit, hot air vents out the back. The unit didn’t come with the original air hose. The vent hole is a standard 125mm size. I bodged an adaptor from a cheap 125mm “flange” and screwed it on. A 125mm hose attaches to that and vents out of the window.

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