I have a intertherm (electric) funace and a/c unit model t3qc 36k(a/c). The problem is a clicking sound or eletrical pop sound for 5 minutes before it will start and sometimes it will not start at all.I have already called hvac tech and he said that it was my thermostat so I replaced the thermostat and it ran 1 day and the clicking sound again but would not start so I replced the contactor, ran 3 days the clicking sound again would not run replaced the capaciter ran but not a full day came home blower working house hot, clicking sound again so I turned all power off for 2 days got to hot so I turned it on cliking sound for about 5 minutes or so and the a/c starts, but not every time. What am I missing or over looking calling another tech is not the answer.

First of all you need to find out exactly which part is clicking in the unit. Have someone assist you and be at the unit when they turn it on so you can find exactly where the noise is from. You have done enough guess work and spent enough money already so lets find out exactly what the problem is this time.