Why do your lights dim when your A/C turns on?

This is an interesting phenomenon that affects some homes but fortunately not for most. It is not indicative of a serious problem, but rather more of a nuisance.


Lights Dim When AC Turns On

The most obvious reason for lights dimming is that the A/C consumes a very high start up current and causes a temporary voltage drop. Other circuits within the main panel may be affected by this drop and cause the dimming.

The following list are things to check to rule out obvious problems:

  • Make sure A/C breaker is proper size
  • Make sure wire is proper size
  • Make sure all connections are tight
  • Make sure you have 220 volts at A/C breaker
  • Check amp draw on all motors in A/C circuit
  • Check capacitator

If all the above check out okay, then we can install a hard start kit which reduces the spike in current draw and eliminates most light dimming.

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