Home Ac Units

When I air filters on the central area, I noticed a gurgling noise coming from inside (evaporator?) Unit when it is running. Is this normal or indicative of a problem?

A second alternative system does not seem to make the same noise when he ran.

sounds like a blower negative flow on the coil top EVAP p-trap on the bottom? Is there a hole before kick p-trap? If so make sure thats covered otherwize it could be clogged coil EVAP they tend to resemble the first sign of problems to a head

It is a good condensate drainage is when the fan is running. If it has not done in the past, you may have a potential problem of leakage of condensate. In some cases, there is access out clean installed in the drain. You can try to blow through it or using a vacuum cleaner to remove all restrictions.