[SeniorSitizen]

It did not drip when cold ac was ON before. Why is it dripping now when cold ac is ON?

As #8 reply states , it will drip or run a small stream if the cooling coil temperature and or drain pipe is below dew point temperature . In humid areas a 5 ton unit may produce as much a 10-15 gallons of water in 24 hours . That dew-point temperature is constantly changing as atmospheric conditions change . It's no different than the glass of iced tea causing a ugly stain on the fine wood furniture because of condensation . Some days maybe , some days maybe not , some days all day and all night or maybe not .

To better explain research - Dew point temperature .

 

[SeniorSitizen]

Suggest to take the advice in reply #13 and have your unit checked by a professional . My hvac tech says service calls are an estimated 10-20 percent because of plugged drain lines . It can cause thousands in floor and or ceiling damage .