I had mold last two times they came to service airconditioning unit. We bought and installed an UV light to stop mold. Is this a legitimate remedy or a scam. Have to replace light once year.
UV lights MAY help kill mold spores and other contaminants. It depends on the intensity, reflectivity and installation, which should be near the evaporator coil.
When I hear "they found mold" I'm also leery --- too many contractors yell mold when in fact it can just commonly be algae, or even dirt. Mold should be tested by an independent lab before any corrective action is taken, other than simple cleaning of small amounts.