I was met at the door when I got home by a panicked girlfriend saying "I think the AC is broken..." Sure enough, the thermostat was on 70 but it was 77 and climbing inside. Luckily I had a spare capacitor on hand and was able to get it back up and running in less than 5 minutes.


A failed capacitor is one of the most common reasons for your AC failing, and one of the easiest to correct. True to Murphy's law they tend to fail on the hottest days...

If your AC system is on, the thermostat works, your fan is blowing, but only lukewarm or slightly cool air is coming out the vent and the temp in the house is rising, it's almost always that the capacitor has failed and therefore your compressor isn't starting up.

Nowadays, capacitors tend to only last 3-5 years.

But you can plan for this ahead of time. Take a few minutes, go to your outside unit, shut off the power at the nearby breaker, take off the access panel (usually in the corner and held on by a few small metal screws), and take a photo of the label on the capacitor inside. It will be a silver cylinder with wire connections on top. It may be mounted in a bracket or sitting on a small shelf.



Then go spend the $20-$30 to buy a matching capacitor and store it somewhere safe for a later date. It can either be the exact same model, or at least one with the same rating (voltage and capacitance numbers) as the current capacitor.

When it comes time to need it, shut the AC off at the thermostat, shut off the power at the outside unit by pulling the nearby breaker, take off the access panel, take a photo of the current wires plugged into the failed capacitor, use an insulated screwdriver blade to bridge the connectors on top to discharge any remaining current, then remove the wires and reinstall them back the exact same way on the new capacitor, just like your photo shows. The wires have basic plug-type connectors on the end, and can simply be unplugged and plugged onto the new capacitor. No "wiring" (stripping/wrapping/crimping/etc.) necessary.

Then power the unit back on, turn it back on at the thermostat, and check for cold air at a vent.

A quick and relatively simple fix for a very common issue. And can save you hundreds of dollars in service fees and hours/days of waiting for a repairman to come do the same.

You can also find various video tutorials online on how to do this, if you need more guidance.


And if you want to be even more prepared, keep a spare contactor as well. That's the black box next to the capacitor in the earlier photo, which acts as a switch to let your low voltage thermostat "talk" to your high voltage outside unit and turn it on/off . Similarly cheap and fairly easy replacement with some basic wire connections, just a less common failure point than the more common capacitor which tends to go out every few years.

Thanks to SF I went out and bought one last year. I’m patiently waiting for the day when it will inevitably happen.

It’s so easy and much cheaper than a service call.

Thanks for the tutorial, RogueJSK.

Thats a great idea. Thanks.

Thanks for the tip.

That is a great tip, replaced mine as a PM and kept the old one as a spare. That gave me time to shop for a quality part.

Bought a "Quality USA Made" Capacitor last summer when we had a similar thread.

Heading off to research the "Contactor".

Cool tip, easy enough instructions to follow, and pay attention to the "insulated screwdriver" necessity and crossing the terminals to discharge the old one. If not it can be very shocking!

I've also replaced fan motors, ours went out and we spent a few days waiting on Amazon to deliver it, local AC supply house gouges civilians on prices, I called and got one price, and then served up a much higher price when I arrived.

Told them to shove it when the guy argued about it and told me buy it if you want cold air at home or not.

Amazon to the rescue, next day delivery, at wholesale level price. Fan replacement is just about as easy and you can find all kinds of internet how to videos.

quote:

Originally posted by HRK:
I've also replaced fan motors

I've done that as well at the last house, though that is a few steps up in difficulty compared to a capacitor that basically any able-bodied person can replace themselves.

quote:

Originally posted by HRK:
and pay attention to the "insulated screwdriver" necessity and crossing the terminals to discharge the old one. If not it can be very shocking!

In theory, yes. So it's certainly worth doing.

In practice, a residential capacitor *should* discharge itself when power is cut.

So not something to be overly worried/scared about, but still worth taking the simple precaution of attempting to discharge any remaining power yourself as a safeguard.

Yes I agree.

Ive had to replace two over the years. I keep spares on hand now.

I do not buy my capacitors from Amazon. I go to the local HVAC supply house. Never turned down as a civilian. Much higher quality.

I'm going to have to check this out on my units. So these are typically in the outside condenser units?

I've never had a home AC fail, but I'm only in my 2nd house which is only 6 years old.

quote:

Originally posted by flesheatingvirus:
I'm going to have to check this out on my units. So these are typically in the outside condenser units?

Correct. On most outside units one corner will be solid, without any vent areas. This is typically a cover panel over the electronics, as shown in my earlier post (with the cover off).

quote:

I've never had a home AC fail, but I'm only in my 2nd house which is only 6 years old.

Sounds like you're due for a failed capacitor, as 6 years is a little past their usual lifespan nowadays.

quote:

Originally posted by 4MUL8R:

I do not buy my capacitors from Amazon. I go to the local HVAC supply house. Never turned down as a civilian. Much higher quality.

Amazon does have Made In U.S.A. capacitors. I keep one of these on hand.

Amrad Capacitor, Made In U.S.A.

quote:

Originally posted by flesheatingvirus:

So these are typically in the outside condenser units?

Yes, easy access, not difficult to change, there are many youtube videos. If you are a total virgin with respect to electrical stuff, you might want someone to show you how to do it, the first time.

This is yet another one of the ten minute jobs that I used to do myself, but now at 89, with increasing mobility limitations, it's safer for me to have someone else do it. My balance is terrible, and I don't need to end up on my ass in the back yard.

quote:

Originally posted by V-Tail:

quote:

Originally posted by 4MUL8R:

I do not buy my capacitors from Amazon. I go to the local HVAC supply house. Never turned down as a civilian. Much higher quality.

Amazon does have Made In U.S.A. capacitors. I keep one of these on hand.

Amrad Capacitor, Made In U.S.A.

Mars also makes a line of Made in USA capacitors (model numbers 14XXX).

As do several other major capacitor manufacturers.

Amazon sells these higher quality US made capacitors from the various manufacturers too, just like a supply house.

So it's more about what capacitor you buy, not where you buy it. Most of the major American capacitor brands offer a more expensive US made line and a cheaper Chinese/Mexican made line.

Wow, thank you, RogueJSK! I am going to try this.

I have a question, and I hope you don't mind. Our unit is about 15 years old. This past spring, our AC stopped cooling effectively and we called our AC people. They said there is a small freon leak, and they put in about 3 lbs of freon.

I went ahead and had them price another unit with the assumption that this unit was going to die, and/or the freon leak would become worse, and I would have to replace it before the summer is over. After I saw the pricing, and my epileptic seizure was over, I thanked them for their help and saw them to the door.

As of today, and I hope I don't jinx myself, I am shocked to say that the unit is running and cooling well.

If/when the leak shows up again, and the unit is otherwise running well, is there a "stop leak" product that can be injected into the AC with the freon to help prevent further leaks?



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Not that I'm aware of, though I'm just a handy homeowner not a HVAC professional.

We do have 1 or 2 HVAC guys that are forum members, so perhaps they will chime in.

And even if there were such an option to perhaps limp it along a little bit longer, at that point I would likely rather bite the bullet and do it right by replacing the system. Keep in mind that a newer and more efficient system will use less power, and may also be eligible for tax credits, both of which can help offset part of the cost of the system over the long run.


Replacement of major house systems like roofs, HVACs, fences, decks, water heaters, etc. is just part of being a homeowner. Entropy is constantly working on tearing parts of your house down. But if you develop the habit of saving a little at a time over the long run, that buildup of home repair savings can help lessen the sticker shock of these big costs every 10-20 years.

For example, $12k for a new roof or HVAC system is a lot to pull out of your back pocket unexpectedly. However, if you were to save $100/month for the 10 years leading up to it because you know it's going to need eventual replacement at some point, it becomes very doable.

Home equity loans are another route for covering major replacements, but borrowing money is a distant second choice.

Excellent reminder and advice. I used bold type for the following quote to eliminate surprises:

quote:

use an insulated screwdriver blade to bridge the connectors on top to discharge any remaining current, then remove the wires capacitor,

quote:

Originally posted by RogueJSK:

And even if there were such an option to perhaps limp it along a little bit longer, at that point I would likely rather bite the bullet and do it right by replacing the system....

Thanks. I am a seasoned homeowner, I am just a bit tight with a dollar.


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