What causes a contactor to burn out?

An air conditioning contactor typically burns out prematurely due to continuous electrical arcing, insect intrusion, power surges, and excessive electrical load. Every single time your HVAC system cycles on and off, the contactor's metal points snap together, creating a microscopic electrical spark or arc that gradually pits, corrodes, and erodes the copper contact surfaces over thousands of cycles, increasing resistance and heat. Furthermore, outdoor condensing units attract small insects like ants and spiders that crawl between the open contact points; when the contactor energizes, the electricity roasts the bugs, leaving carbon residue that accelerates burning. Voltage drops and brownouts also strain the electromagnetic coil. You can prevent burnout by keeping units clean and inspecting switches. You can verify a healthy contactor when points close cleanly without buzzing or charring.