3 split units run from one compressor one is not cooling

SOURCE: Will Not Heat

On the outdoor unit the fan should not be running, on the indoor unit the fan should be running. If you then check the outdoor unit with fan not running, you should be able to hear clearly that the compressor is actually working. If this is all correct, it is possible that your fourway reverse valve is seeping and needs to be replaced.

SOURCE: Fujitsu Air Conditioning split unit Model

Your compressor is seized up. shut down unit and let compressor cool down, it may start again but probably needs to be replaced.... sorry for the bad news,

SOURCE: Celiera 12000 btu Mini-split ac unit blows cool

It's 'possible' but not likely that you need additional freon.

What is more likely is the 'filter' (for inside coil) is dirty and possibly the coil itself - and/or - the outside coil is dirty.

I would check out the filter - if dirty - I would change it and would also inspect the inside coil. If it's also dirty I would clean it the best I could (with a brush of some sort).

I would also check the outside coil and clean it if need be.

Hope this helps.

SOURCE: Hi ...we have a split

There is a relay that the thermostat pulls in, in the unit outside. When this happens, the compressor pulls in and the unit outside will run. The compressor has to run before the unit will cool.

SOURCE: My Fujistu AST9LSACW split system

There are two things you can check outside before calling a service technician. The first is the breaker to the outside unit. There is a breaker or disconnect near the unit. If there is nothing wrong with the electrical supply, check the refrigerant level. If the level is low, the pressure switch will cut off power to the compressor to protect it from damage. DO NOT try to recharge the compressor yourself.