AC capacitors

Related to the thread on heat. If you have some comfort with electricity and are a little mechanical, take the little cover off outside and get a picture of the capacitor(s) including part numbers. Order a replacement online or go to like Grainger. They are cheap insurance. You can be back up and running in a few minutes. Also a lot less $s.

Check out a few YouTube videos beforehand, like this weekend. You might even find one close to or exactly like your AC. Electrical gloves and a multimeter are handy but not required.

They always seem to go out at the worst time.

I’ll thank you later.

That is very good advice

Be aware that a capacitor can kill you

ALWAYS safely discharge a capacitor before handling it

Pics are real handy getting the wires back in the right spot.

Turkey is spot on this happened to me the other day. Good to have a spare or two per unit

Agreed with all the points here. The capacitor is the main thing to pop on the outside units…a lot of times you’ll be able to tell it’s popped because, well, it popped and the cap separated. But in any instance, absolutely be sure it’s properly discharged

I started doing residential HVAC with my pops at around 5. He taught me about it all. I’d go every summer and break to work with him until he got back into commercial about a decade later. Looking back on those times, it’s amazing how many folks I see nowadays always doing complete new systems. I don’t even hardly remember a time my dad and I went for a service and recommended a full system. Probably why my dad didn’t last in that arena, he wouldn’t sell you something you didn’t need. 95% of the time we got called out in the summer was for an inop system due to failed capacitor or a fan motor

It’s extremely unlikely to get killed by an AC capacitor where you have the breaker turned off. Most commonly you would get a memorable shock. Some electrical gloves from the hardware store are great for peace of mind. Plus they are handy for your home tools just like a multimeter.

Discharging a capacitor is very simple.

As mentioned in this thread, usually the bad capacitor is bulged. Another handy thing about a reference photo.

So how do you discharge a capacitor?

Capacitors store a pretty good amount of energy in them, so don’t believe that having the breaker off means it won’t do anything to ya

I’d say try putting your tongue across the terminals like a 9V battery but there may be other ways 😂

As stated, a charged capacitor will give you a memorable shock. It’s unlikely to kill you. But there’s no reason why anyone with half a brain should ever get shocked by an AC capacitor if they read and follow instructions, video etc. If you’re smart enough to dig a post hole, you can safely change an AC capacitor.

Good advice. Just had one replaced on three year old unit yesterday. $195 weekend service call. Ouch!

I've heard most of the info above--except--the electrified part. I've been meaning to get a capacitor because I figured I could easily change one.

One of the videos I just watched said that if you touched one side with one hand and the other side with the other had that the voltage could potentially travel through the chest and heart. Sheeeite I didn't know that, but I do now.

One guy discharged it in about a second with a screwdriver across the terminals, while wearing rubber gloves and safety goggles.

Sounds like a hellava idea. Have somebody take video of said process.

Search “how to discharge an air conditioner capacitor”. There are several methods. I’ve always used a screwdriver or pointed nose pliers.

I first started working with large capacitors in ham radio linear amplifiers as a teenager. Also old TVs. They could whack you pretty good. People in electronics have probably tossed a friend a charged capacitor as a joke. I have tossed and received.

I would suggest also getting a spare contactor (which is really just a high voltage relay) because like start capacitors, these eventually wear out too.

And remember not all your local parts dealers like to sell to DIY'ers in order to protect the market for the ones who want to charge you $250 for the five minutes it takes them to replace a $10 capacitor.

Yeah, I think I'd want to be confident about what I was doing before changing one out.

I'll research it before trying to replace one.

Myself and most I have seen did not use either. However, it's all recommended PPE and a good idea.

For example consider using a chainsaw. Here's what you ought to have on for PPE.

- safety glasses
- work gloves
- hearing protection
- safety boots, i.e. steel tips, maybe even metatarsal boots
- fall arrest system if up on a ladder or in a tree greater than 6 feet

Might even be missing something there but you get the idea.

Capacitor isn’t covered under warranty?

I always keep a spare in the cabinet inside. You can buy them on Amazon cheap. I recently had to fly home early from a fishing trip because the AC quit on my wife and at 110 out ,nobody was available for days and I am sure they would have charged her for something that may have not been necessary. It took all of 15 minutes to replace and was sure a relief for us both.

Maybe but could take a couple of days or weeks to get an authorized tech for a normal daytime service call. The parts and normal labor rate may be covered but it's going to be ~$195 for an after-hours or weekend service call.

Yep - these days capacitors don't last nearly as long as they used to in the good old days when they were filled with PCB's !

Most of the time no and if it is more than like labor isn’t and that’s what going to cost the most. New units sometimes have a 10 years parts warranty if registered and if not registered sometimes the manufacturer will knock it down to five years. Some of the manufacturers will do a parts and labor warranty but it generally doesn’t cover overtime and the tech on the weekend doesn’t have that info.

The size of the capacitor is different depending on the tonnage of the unit and you should never go under or over what is required or damage can be done to the compressor over time.

As far as discharging a capacitor once I have it out and the wires off I either put a screwdriver or needle nose pliers across it or touch it to the cabinet of the unit.

Actually, suppliers are just cant stand the liabilty of selling to home owners. No one takes responsibility for thier actions, it is alway some one else's fault.

Example. Guy called me, descibed his problem. He informs me just replaced cap. I ask for a pic. I advised he missed wired. He wants to argue with me.

The labor charge is not for the time to replace part, charge also includes costs of truck with an inventory , insurance, taxes and $1000.00 worth tools.

Another option.....One could always pull the unit and take to shop, tell them what to replace.

I ain't touching nuttin that can bite me. That's why AC Cat's are called professionals.

Good advice!! I've already gone through 3 in the last 4 years. It cost $175.00 each time to fix it.

You mean like having to take your car to the dealer because the auto parts stores won't sell you some brake pads?

Lots of good YT videos on the subject. I`ve never had to replace one, but I`m going to get one to keep on hand. Discharging the Capacitar is the most important thing after cutting off the power supply. I actually watched one video where the AC Tech cut off the powers supply and still got shocked. Use a multimeter to make sure all owe is off. Safety first.

Dan, point taken. It is apples and oranges in my opinion. Different businesses. One is retail the other is business to buisness.

Any manly man should have the wherewithal to safely diagnose and swap the contacts, capacitor or blower motor in his own home AC system. But I understand if you are really wealthy and it’s not worth your time. It is beyond the capacity of a typical man bun wearing beta male.

It will give you more than a memorable shock.

Got bit by 120v replacing a ceiling fan in college.

It really hurts.

Those units are typically 240v

Always kill the service disconnect on the outside of the house and test the contactor with your multimeter before you touch anything.

When the capacitor goes bad does the unit shut down or keep running just not cooling?

Sounds like a court case to me!

Truth. Sounds like all my neighbors.

My unit continues to run but does not cool when the capacitor goes bad.

It will depend if the system has a high pressure switch or not. If it does not the compressor will continue to run until it shuts off on thermal overload. If it does once the pressure of the switch the compressor will shut off but could come back on if it is an automatic reset switch.

It depends if the cap is weak or dead and if it's the run or start cap. There are start/run caps for the outside fan and the compressor as well as caps for the air handler fan.

Do this!

most resi outdoor units use a cap that has the cond fan and comp cap in one. the fan part could fail and compressor continue to run, for a little bit, or the comp side fail and the cond fan will run if the call for cool is there. the comp terminal is the herm, f is fan, c is common. amrad is the brand of cap you want. if you have inverter or vari speed, two speed outdoor unit, this wont apply.

An ear familiar with how these systems operate can often identify the problem by sound and observation alone.

Much like figuring out what's wrong with the wife.

Often times, it’s not the actual shock that hurts you as much as whacking your hand against something sharp or hard as you quickly retract your appendage due to the shock.

No sound or action can be just as much an indication that something is wrong on your account.

Ya'll don't kid yourselves on these AC caps - they can store up to 1400 Joules (or more) of energy - at 220+ volts (even when power is off) if not properly discharged.
Just for reference, a strongest electric fence is around 40 joules - and a heart-defibrillator machine goes from 100J up to 360 Joules max !
Be safe out there.

What mine did.

Parts dealers don't like dealing with clueless homeowners for many reasons. In fact, I know several who inflate the prices on items they will sell to unlicensed homeowners, mainly because y'all are a PITA to deal with.

As for you analogy of a $250 service call for a capacitor, you obviously don't have a clue what it takes to run an AC business in today's economy. So go spend about 20+yrs in the industry then get back to us with your opinions on how unfair prices are.

You'll swap a capacitor, then the contactor, not knowing if either will fix your problem. You're just hoping.

Yeah, I might charge you significantly more (see my second statement above), but I'll diagnose the problem, change/fix whatever is truly bad, and get your system up and running again. The biggest difference in all of that is I know why I am doing what I am doing, you are changing parts that someone on the internet told you to change, hoping it runs when you are done.

As far as Cap's being dangerous......Electricity is dangerous at any voltage/current in the wrong circumstances. I've been shocked in more ways than I can remember, with voltages ranging from 24vac up to 680v. My worst experience was with 120volts, but conditions play a huge role.

Two ways to discharge a cap. Get the unit/component running then kill the line voltage via a breaker or disconnect upstream (not control voltage), and the cap will drain. You can also short across the terminals on the cap with a screwdriver or other sacrificial tool with an insulated handle. I usually do both. The first method isn't always an option, but the second will make sure you're not cussing yourself and tasting ozone.

I agree 110% with paying a skilled technician a fair price for their time, experience and service they provide. We see the same thing on THF every deer season when people complain about deer processors charging too much for their services. Everyone thinks other people should work for cheap except them. First thing, my AC experience stops at replacing the air filter. I`ve always called the man when I`ve had an issue with mine, but after watching numerous videos on the subject I wouldn`t be afraid to tackle it. Right or wrong, I do think a person has the right to try and fix it on their own if they want to. YouTube has helped save lots of people a lot of $$$ over time. If I replaced it and it till didn`t work, I could still call the man.

I am the quintessential DIY guy myself. I refuse to pay someone to do something I can do for myself. I'm 100% in favor of people learning how to work on stuff. A/C is not quite rocket science, but there are intricacies in the refrigeration process that can make a symptom appear as a problem, treat the symptom only and the problem still exists. Having someone who understands the whole process often means the disease gets cured, not just the symptom. That being said there are times when I know I am, or will be, out of my depth on certain things. When that occurs I realize full well that I am paying more for the person's knowledge than the actual labor. And having been involved in almost all aspects of the HVAC business, I also realize that there are costs far over and above just the labor of the person working on my stuff when it comes to running a business. So many have no clue and are quick to criticize pricing when it comes to stuff like that.

A/C technicians are the most loved and hated tradesmen on the earth, even by other trades. Our trade requires we have at least a basic knowledge of just about every other trade out there. So even in commercial or industrial, it's difficult to BS a seasoned HVAC tradesman, though many still try. I quit doing residential work over 10yrs ago and don't miss bipolar, whiny, overly-demanding, quirky, cheap, clueless homeowners one bit. Not all homeowners are that way, but one is all it takes to screw up a day, and it seems there was at least one every day. That being said, residential is the training ground for noobs in the industry, it separates the wheat from the chaff. Some like it and remain, others move on to commercial or industrial at their first opportunity and never look back.

Well said. I have standard warning for new guys. We are heros or zeros, never anything in between. You will not have the authority to correct other trades work, but you will be responsible to diagnosis and suggest a correction.

Finally took the cover off my 6 year old Trane XR unit yesterday and took pictures of the capacitors and contactor. Was able to match up the correct part #`s within an hour on amazon and ordered them. Should be here by Saturday.

Yep, always keep at least one spare on hand. My wife was even able to replace one when I was out of town.

Wise words. I actually just went out and replaced one of my caps. You never know when you'll need one, and you also don't know if all of them will work out of the box (there are a lot of defects). Buy 3 at a time and you'll save yourself headache in addition to saving coin

I have changed one out on a RV. The instructions I had were about the same as we see posted here, Needing to discharge the capacitor and kill power to the unit. The one I changed was "swollen" and had a burned electrical smell.
Is the contactor located near the capacitor?

Is a residential split system the contactor will be close to the capacitor and the common wire will come off the contactor to the capacitor.

What is your opinion or advice on a soft start kit ? I have an older Rheem 3 ton that sometimes dims the lights when starting however the unit keeps my house at 65 degrees and cycles when the Temps are 108 degrees we also have a lot of power interruptions so far this year we have had 14.

It would be great to have if you were ever using a generator.

Yes sir, generator is a must have with so many electrical interruptions. Thank you tpack for the advice