mould above air conditioner

At tenants request I installed ceiling fans in two top bedrooms then they said it still wasn't cool enough and requested ac so I installed an air conditioner in each of these bedrooms. Now they have mould in the vaulted ceiling above the air conditioner. Anyone know what could be causing that or had a problem with it?.

 

Are you sure the installer put the tiles back on the roof.
Unusual one
Are the A/C's installed on external walls? If they are wall mount the drains will drain straight out the back of the unit. If installed on internal wall they need to pump the condensate water away
If refrigerant pipes are not insulated properly they will sweat

 

yes, on external walls. I wonder if the ceiling fans are turned upwards and therefore throwing cold air straight up into the corner

 

Have you sent anyone around to check the mould issues from last week? The problems may be connected.

 

Did you check the roof tiles. If they ran dedicated electrical circuits they usually run the cables through the roof and they feed the cables down through the eve into the refrig piping duct. They would need to take the roof tiles out above the AC to do this.. If tiles were left out and it has rained then that would cause mold above the unit.
Won't be the fan blowing the air into the corner. For that to cause an issue the Gyprock would have to reach dew point which is highly unlikely

 

Also if the installs are not back to back and the pipes run up into the roof cavity, moisture problems can occur if the flare nuts are not insulated after the piping connections are done. The joints will sweat and pool water in the roof.
If its a back to back then the pipes will go through the wall and down the pipe duct which won't cause any issues.