Sooo our a/c just quit...
 

...working and it's 94* outside and 85* inside.
There's a humming sound out at the condenser outside that sounds like the motor is trying to start but can't. We just had the system serviced back in January, all was good, even after 10 years without a service call. I can spin the fan with a screw driver thru the protection screen so the motor isn't seized up. It was working fine this morning, or so I thought.
This will be interesting...

So, the fan is not running, and neither is the compressor. It is most likely the capacitor.

That's what I'm thinking but I'm no expert and I didn't sleep at the Holiday Inn last night either so I'm waiting to hear from the 'guys' that looked at it last.

Run capacitor

That's my thought, capacitor. The motor needs a jolt to start and then will run on regular power. A capacitor provides the jolt, unless/until it goes bad.

LOL. I'm not an expert either...but fix six or seven a year. Simple compared to even the easiest problem on a 911.

Usually the cap, but recently had a bad contactor (just a big relay) ...but can't be sure without testing. Also had a bad compressor on one and had a pro replace it.

Good luck...too hot for bad A/C.

And just in case... the $340 portable unit that Lowes sells isn't bad, seal off a smaller area (large bedroom etc) and it does the job. Had AC go out 2 weeks ago in similar conditions and the redheaded wife is going thru menopause. Literal life saver.

I sometimes work on tube amplifiers and those capacitors are perhaps a very different animal, but you do have to be VERY careful around tube amps because those capacitors can store lethal voltages. One of my amps has a circuit using several capacitors and operating at just under 600 Volts. I'd be comfortable swapping out a heat pump capacitor, but I would use a procedure that assumes the worst. I would NOT go anywhere near the guts of a microwave oven. FWIW.

Turn off power

Short across cap leads with screwdriver that has insulated handle

read capacitance value and voltage rating off fan cap or dual cap (if its the same one for compressor), dual cap will (obviously) have 2 pairs of ratings

order like part off amazon for 10-20$ (voltage rating can be higher)

82.5% chance that fixes the problem without a 200% service call, you may be able to source the cap locally at an ac supply store. Hopless despot and similar places don't seem to stock them in my area I think for legal reasons

My fear of electricity far out weighs my desire to be cool or to escape the wrath of my wife for it not working. Trust me on that.

I've posted this before.

You can use a portable AC, as mentioned by id10t, above.

Or.....I have a standard window unit that can be used in situations like this. It's only 5K BTU, but that's more than enough to maintain enough comfort to allow some flexibility on repairs to the main unit.

They are 110v, under $200, and well worth it.

I'll just put a block of ice in a pan and set in front of the fan my wife has constantly blowing in the family room. That should do just as well and be a lot cheaper too.

Our capacitor was replaced about a year and a half ago. I’m tempted to see what size/make it is and have one on standby.

Mine went out Saturday morning with symptoms the same as yours. It was bad capacitor.

My biggest concern was finding a place that would sell one to me NOW. I got that arranged through a master electrician 200 miles away.. Took longer to get the part than to fix it.

If you are fixing it yourself, look at the microfared numbers on the capacitor. Yours may be a dual capacitor like mine, which is the compressor (Herm) and fan. Mine was 40+5 440v.

Easy job, just don't forget kill the power to the unit (condenser) and then discharge the capacitor first.

Amazon sells capacitors, but I couldn't wait until Monday.

I wouldn't even know where to begin looking for a capacitor on the unit much less be able to get in a position to take it out. I'm old and don't bend like I used to.

It's a good idea to have a spare on hand.

I thought the same. Mine was three 1/4 inch machine screws for the cover, 1 screw for the capacitor retaining band. Then it was just 4 wire connectors, two for common, 1 herm, 1 fan.

Give it a shot!

I'll watch real close when they come to fix it and maybe do it next time, if I live that long.

I'm assuming your process is correct, but rather than ordering from Amazon, I would find a local shop where you can buy one. I've bought at least one or maybe two in the past, and was able to source them locally, usually in 30-60 mins once I'd determined what the problem is. Find a couple/few HVAC parts places, call around, "do you have capacitors? Do you sell to someone that's not a contractor?" And yeah, they are usually super cheap.

I stock the capacitors and motor contractors for all my AC units.

After shutting off the power to my Trane heat pump to replace the capacitor, I learned the hard way that my system has a 30 minute delay following reenergizing the system.

How do you discharge the capacitor?

I have a 100 Watt 25 Ohm resistor. Some people use a screw driver. They bleed down eventually. I check with a Volt meter and discharge if necessary.

Just to close this thread out, it was the start capacitor.
I mentioned I'd posted here and everyone thought I should replace it myself. The guys confirmed that getting someone to sell one to me was a problem.
This is only the second time in 10 years we've had to spend money on the system so I'm not too worried about the bill.

When you have to replace a capacitor, try to find one made in the USA, (this will be difficult). Failing that, find one that’s made in Mexico. Do not install one that’s made in China.

I have a couple of spare capacitors that I bought for $30 after going without AC for a day and spending $150+ to get it repaired.

I definitely keep spare caps on hand. Really nice to be able to replace these things with out waiting for the amazon guy or running around to AC supply stores (which always seem to close at like 4).

For the fan start cap you can give the blade a with a screw driver or something and it will spin up. Works in a pinch if you need to cool the house.

Single phase AC induction motors seem so archaic and crude in the year 2022, but they work and are simple I suppose.

Scott,

Glad it worked out for you - easy fix - so not too expensive.

You can get these from Amazon. Grainger as well. Other places. I bought from eBay in the past also.

If it's something you don't want to mess with - I respect your decision.

Happy Friday! SmileWavy

That's a good point. I tried that and the fan worked, but the compressor did not. My capacitor is a dual purpose. I wonder if its possible to only blow half of the capacitor on a dual.

I had replaced our capacitor after the cooling fan was running, but the compressor would not kick on. A few days later we had a very momentary power blip. I went to check on the ac unit, and same thing, the compressor was not running. I rigged up a small hose and had it wet down the compressor to cool it down. 20 minutes later, I removed the hose, and fired it up. When the thermostat finally decided it had been long enough the compressor came to life, and all was well. That was 45 days ago, and we have had a lot of HOT days.

I still need to restock with a fresh spare capacitor.

My Fluke 75 meter does not have the setting for checking the capacitor mention in that excellent video above. I have had my Fluke for 35 or 40 years.

One way to test a capacitor without using a meter is to touch the two magic terminals with your two index fingers and measure how high off the ground you are launched. All you need is a wooden ruler and a witness.

Legal disclaimer: Do not actually attempt this, it will kill you and all of your unborn children.

‘Reckon so…

I have one of these reasonably priced grey market flukes with cap checker.

They are real fluke but intendend for low cost markets. Same fluke quality and a bargain imho though. No fluke warantee or us support however


https://www.ebay.com/itm/373557024598?epid=26041733181&hash=item56f9bbd756: g:h5oAAOSwg2lgh7YE

Yep, that's why they're measured in microfareds. It's a low fare short ride.

Guaranteed to be painful and probably surprisingly loud, as well.

I doubt there are very many repeat customers.

I looked at the box and recognized the name from one of the videos here but I forget which one. I watched the guy change it out and he didn't really check to see if it was discharged but he was very careful to only touch one wire at a time.
I should have photographed the whole deal. I know where it's located now and what kind of contortions I'll have to go thru if I ever have to change it again. We don't use it all that much compared to what most of you do, but it has been used more in recent months as it seems the weather has been a lot hotter than it usually is.

The best part is Baz, that my wife won't blame me for it not working since I didn't fix it.

My fear of electricity comes mainly from an experience my cousin went thru that ended up killing him. He was about 10 yrs old and fishing on a private lake in an aluminum boat. They went under a bridge of some sort and he reached up and touched it. Something hadn't been wired correctly and he was electrocuted. I never really helped my dad out much when he was working on electrical stuff at our house as a kid. He had studied and taken the exam to qualify himself so he could work on the house without needing a paid professional. I wish now that I had paid more attention to how things were done but that's water under the bridge now.

Just be glad you did not need refrigerant now. You would have to contribute an arm or leg...and then in a few weeks, it would all leak out and you would be back to square one.