ac stopped working, anything i can do to diagnose?

Check the capacitor.. if you don't know how best to call someone in as you could hurt yourself.

My Brother came home last weekend to no A/C. Turns out an earwig had committed suicide in the contacts of the relay. He cleaned the relay and sanded with 400 grit to get the contacts to engage again. He literally debugged the system. Wednesday my parents A/C failed, needed a new starter capacitor. Could easily be one of those.

Had such a failure 3 weeks ago. If you can hear the compressor humming but not running, it may be the capacitor (since you say the contactor apparently works). This item is not something you can buy at a BB store. Always best to have a spare on hand.

Turn on the AC and give the fan a push with a small stick or something small through the grill. If it starts spinning then it is probably the capacitor.

If you are capable of testing the capacitor then try that. Here is a video on how to do it, and there are many other videos you can find on youtube -
If you cannot then just make sure its all turned off, you dont want to run it as you could burn out something and cause more issues.

Not sure where you are located but if you don't have a Reliable/Honest HVAC tech you may want to reach out to @newlyborn from - fair deal heating and air conditioning Hes one of the recommended HVAC companies on RFD & Services Toronto & the GTA, he may even be able to come out to you today if your in his service area.

sickcars wrote: ↑ If you are capable of testing the capacitor then try that. Here is a video on how to do it, and there are many other videos you can find on youtube -
If you cannot then just make sure its all turned off, you dont want to run it as you could burn out something and cause more issues.

Not sure where you are located but if you don't have a Reliable/Honest HVAC tech you may want to reach out to @newlyborn from - fair deal heating and air conditioning Hes one of the recommended HVAC companies on RFD & Services Toronto & the GTA, he may even be able to come out to you today if your in his service area.

Please don't tell someone if the power is off its fine.. a capacitor is a storage device and can store considerable amount of electricity.. that can be discharged if you don't know what your doing.

You misunderstood me, I was saying if hes not capable of testing it then make sure the AC is turned off so you dont leave it running and kill the compressor until an HVAC Professional can come out and check it for him. I'm not saying just unplug it and you wont get shocked.

TLSRULZ wrote: ↑ Please don't tell someone if the power is off its fine.. a capacitor is a storage device and can store considerable amount of electricity.. that can be discharged if you don't know what your doing.

sickcars wrote: ↑ You misunderstood me, I was saying if hes not capable of testing it then make sure the AC is turned off so you dont leave it running and kill the compressor until an HVAC Professional can come out and check it for him. I'm not saying just unplug it and you wont get shocked.

Agree.. I read too fast..

Clicking sound indicates that furnace board is ending signals ( 24V ) to the AC for contactor to engage. If Fan and or compressor are not turning on, it could be due to bad capacitor or contactor as @Jerico has mentioned in his post
If you plan to test and replace capacitor yourself, @sickcars have provided you the youtube link. Just be extra cautious. Even though I am doing this for many years, I still wear gloves when changing capacitor or contactor on AC besides taking all other necessary precautions.
It will be nice if you report back your findings as it will help other fellow members.

esoxhntr wrote: ↑central AC stopped working today, checked the obvious; breakers, switch outside, filter

i can hear the unit outside click when the call for cooling is made (and again when I shut the AC 'off'). but nothing happens other than the blower in the furnace turning on.

it's likely beyond me but wondering if there's anything i can check before calling the pros on monday? could a clogged condensate line or faulty condensate pump trip some kind of safety?

it could very well be time for replacement.

Jerico wrote: ↑ My Brother came home last weekend to no A/C. Turns out an earwig had committed suicide in the contacts of the relay. He cleaned the relay and sanded with 400 grit to get the contacts to engage again. He literally debugged the system. Wednesday my parents A/C failed, needed a new starter capacitor. Could easily be one of those.

Clicking sound indicates the 24 volt power from thermostat is activating the relay, however as others have said, im no expert but it sounds like it could be a capacitor failed. this is common in the warm summer months, this happened to me years ago

Thank you everyone for your input. As well as the warnings.

It was the capacitor, I did the test on it.

The unit was between 15-20 years old, I have decided it was time to replace as it didnt seem as efficient as it used to be anyway. Today it's the cap tomorrow it's something else.

esoxhntr wrote: ↑ Thank you everyone for your input. As well as the warnings.

It was the capacitor, I did the test on it.

The unit was between 15-20 years old, I have decided it was time to replace as it didnt seem as efficient as it used to be anyway. Today it's the cap tomorrow it's something else.

Caps are cheap replaceable items. $20-30.

thriftshopper wrote: ↑ Caps are cheap replaceable items. $20-30.

they may be cheap, but they're definitely not a Do It Yourself job, if u have no knowledge of how they work you can get a nice shock or jolt. you have to discharge them before you tinker, many people dont know this