We have an older central a/c system that stopped blowing cold last night. Everything was working fine including exterior fan running fine, but the compressor itself was not kicking in. We could tell it was trying to come on (house lights dim a tiny bit when it kicks on). The interior unit is working well - has a new motor & new capacitor - so we know that isn't an issue.

Is it possibly the capacitor on the exterior unit? We took it apart and looked, and the capacitor looks ancient and has some rusting around the top. We believe it is (at the very least) 13 years old. We took it off & will pick up a new one tomorrow as our first step to try to replace that. We also cleaned coils & replaced the interior filter.

Any other suggestions as to what we could check?

 

Replacing the capacitor is a good first step in diagnosing a problem like you have there.

 

Thanks. My husband bought a new capacitor & will be installing it later today, so hopefully we will know more at that time.

There is also a 2nd smaller plastic-cased capacitor on the exterior unit, close to the larger metal cylinder capacitor. He's buying a new one of those as well, but it won't be available until tomorrow.