Trane 4 zone mini split system

[Csvt18]

I have a weird issue I have a Trane mini split system with 4 wall units inside and the main heat pump/condenser outside.

Largest unit is in living room first floor. It’s a 21,000 btu unit. 3 others are in each bedroom. All those are 18,000 btu.

I noticed that if my large unit is on and cooling the bedroom units cool effectively as well. If the large unit hits set temp and is just blowing air OR off, the bedroom units don’t cool nearly as effectively. Sometimes they won’t even hit set temp.

What would be causing this?

 

[Fitter30]

Low on refrigerate or condenser is dirty. Both should throw a code if problem is bad enough. Condenser coil is a muilti section coil than would need to be separated to be cleaned properly. You tube video might show how to clean it.

 

[Sponsor]

 

[WorthFlorida]

Need to get a tech on it to check the pressure. Since you are in Michigan with freezing temperatures, threaded fittings can contract that can cause small temporary leak. You might lose an ounce or two of refigerant over a winter but after several winters it adds up. Low refrigerant may also cause freezing on the inside wall units. The unit in the living room, check its coils for ice.