Hey,

I've got a System 4 Toshiba aircon. It's about 8 years old.

We mostly use the 3 units in the bedrooms.

The problem we have now is that when all 3 units are on, only 1 rm gets cold. When 2 or 1 unit is on, the aircon is fine.

I'm assuming there's something wrong with the compressor? Any ideas?

Most probably there is some gas leak at the compressor or the compressor is become weaker due to wear and tear.

I believe you might need to get someone to go and check for you.

I had the same problem before, compressor needs to be inspected, like summerforce mentioned, likely due to wear and tear, our contractor previously have to change the electrodes??? (not sure) because its spoilt already 

spoilt most likely

Best to get someone to check this issue out.