A/C Condenser fan has difficulty starting

[75gmck25]

I turned my house A/C on for the first time this year, and set it to 75. Overnight it got down to 77 and then stalled there (inside unit fan was still running and moving air). I turned it off and let it sit for a couple of hours, and then turned it back on with the temp set to 75.

Went out to check the condenser and noticed the fan started to move and then stopped. Banged on the motor housing a couple of times with my fist and it suddenly came up to speed. Its now been running for about an hour, and after it got to 75 degrees I set the temp down to 73 and its still cooling fine. So far it has not cycled off, so I don't if a restart of the fan will be an issue. I just wanted to make sure it would keep running and working.

Its a Bryant unit (3 ton?) that was installed about 12 years ago and IIRC it uses 410 refrigerant. Is this just a symptom of the compressor fan motor going bad?Do I just look for a data plate on the fan motor and buy a new one?

Thanks for any input.

 

[larry4406]

Perhaps contactor is worn out?

Banging the unit engaged the contacts?

 

[rust in the eye]

Any noises?
Humming when attempting to start (capacitor)or whirring/grinding, vibration (motor bearing) while running?
Condenser fan is an easy fix, usually a very standard size motor so no need to be sodomized by the OE.

 

[mattthemuppet]

failing fan start capacitor or failing fan motor bearings would be my first guesses.

 

[75gmck25]

It seemed to be just the condenser fan that did not start. I could hear a humming noise, but assumed that was coming from the fan motor. The only part I could reach was the top of the motor housing, so that is where I thumped it with my hand.

I will have to take off part of the housing to get a better look at the condenser. It looks like the fan is independent of the condenser itself; however, it happens to be raining right now and I want to wait until later to do any detailed troubleshooting.

 

[Buckaroo5]

Really sounds like the capacitor. Could test it if you have the right kind of multi-meter or visually inspect to see if it is swollen. If not, when trying to start, carefully give it a spin. If it starts, definitely capacitor. Easy and cheap to replace.

 

[mm08822]

If when the condenser starts and the fan just hums, give it spin with a stick or screwdriver. If it then runs, the start cap is bad.

Pull the control panel cover off the condenser and read the specs on the cap.

It may be either a dual cap or 2 seperate caps. Buy replacement(s) and switch out. They are old enough to be at/near end of life.

Get the specs for the contactor also while in there.

 

[micromind]

See if it starts next time. If it does, most likely you jarred old grease loose by hitting it.

Those motors are usually the PSC (Permanent Split Capacitor) type. It's just a motor and a separately mounted capacitor. Often the compressor and fan capacitor are in the same can, 3 leads rather than 2.

I've found that the majority of failures in these types of motors are the capacitor. Not very expensive and easy to replace.

If you're going to work on it, shut off the power at the breaker or disconnect switch. Most of these units will break only one of the two hot legs to turn it on and off. This means that just about every wire inside is always energized.

 

[Chuckster in NJ]

Possible bad capacitor.

BTW! The motor "hums" because it doesn’t know the words to the song and if you can’t fix it with a hammer it is most likely an electrical issue.

 

[mm08822]

Possible bad capacitor.

BTW! The motor "hums" because it doesn’t know the words to the song and if you can’t fix it with a hammer it is most likely an electrical issue.

If I had a hammer couldn't i make it sing in the morning?

 

[loganb]

Sure sounds like the cap, $15 or $20 bucks online...likely $175+ on a service call.

 

[Chuckster in NJ]

If I had a hammer couldn't i make it sing in the morning?

How about the evening or all over the land?

 

[Chuckster in NJ]

TIP! Buy a capacitor (inexpensive) and give it a try and if that doesn’t fix the problem put it away for the future because this is something every DIYer should have in stock.

https://www.supplyhouse.com/Dual-Motor-Run-Capacitors-19701000

 

[The Cobbler]

and when touching or changing the capacitor make sure there's no voltage stored by shorting the terminals to ground

 

[bonneyman]

Possible bad capacitor.

BTW! The motor "hums" because it doesn’t know the words to the song and if you can’t fix it with a hammer it is most likely an electrical issue.

The singing duet (motor and cap). Hilarious!

 

[fitter30]

If buying a aftermarket Don't buy one from hp use amperage. If factory motor name plate states 4 amps and a 1/4 hp replacement is 3.9 amp Don't buy it step up to a 1/3 hp motor. Manufacturers play with rpm ,hp and amps. Aftermarket might be 1050 rpm. Factory 1000 rpm to 1100 or anything in between. If its hanging by the motor bolts buy nuts If they carry them.

 

[Junkman]

While you are working on it, clean the coils. You will be surprised by how much dirt and pollen they attract. I use a cleaner labeled "safe for air-conditioning condensers" from Simple Green.

 

[75gmck25]

Thanks for all the input. Sounds like the capacitor is the most likely culprit.

Weather has now turned colder again (no A/C needed), so I have time to take the covers off and get numbers from the capacitor. Based on what I can see, a good cleaning will also be beneficial.

 

[Innovate1]

Might as well give the shaft a twist to check the bearings too. The flywheel effect of the fan blade makes it hard to get a really good feel for the condition of the bearings as that tends to smooth out any minor roughness but if they are really bad you can feel it.

 

[BurtEggley]

yes, most likely the capacitor. Get a good brand. HVAC guy on Youtube has lots of videos where he checks and replaces caps. They can last a year or they can last 20 years. If the contactor is pitted do that too.

 

[Just_Steve]

Thanks for all the input. Sounds like the capacitor is the most likely culprit.

Weather has now turned colder again (no A/C needed), so I have time to take the covers off and get numbers from the capacitor. Based on what I can see, a good cleaning will also be beneficial.

make sure you note wire position on the capacitor as some replacement caps are universal and can be wired multiple ways.

 

[75gmck25]

The AmRad capacitor I found online appears to be an exact match to the old 35/5 370 volt capacitor, but it's now rated at 440 volts.

I ended up going with an Amazon vendor because they had a brand I recognized and they could deliver quickly. Its supposed to arrive here today.

 

[micromind]

The AmRad capacitor I found online appears to be an exact match to the old 35/5 370 volt capacitor, but it's now rated at 440 volts.

I ended up going with an Amazon vendor because they had a brand I recognized and they could deliver quickly. Its supposed to arrive here today.

Using a 440 volt capacitor to replace a 370 is perfectly fine.

The mfd needs to be the same or very close, the voltage needs to be the same or higher.

 

[dscheidt]

Using a 440 volt capacitor to replace a 370 is perfectly fine.

The mfd needs to be the same or very close, the voltage needs to be the same or higher.

370V is very close to max voltage a capacitor should see in normal service -- 240V is the RMS voltage, so the peak voltage is ~340V, and class B overvoltage of 8% pushes that to ~367. Increasing the voltage rating of the cap will almost certainly improve its lifespan.

 

[75gmck25]

Capacitor came in and I have it installed. Turned the A/C thermostat down and the unit cycled on, but its too cold out now to really try it out. We had 80+ temps a few days ago and now its only about 50 degrees. You can never get warm weather when you need it.

 

[larry4406]

Capacitor came in and I have it installed. Turned the A/C thermostat down and the unit cycled on, but its too cold out now to really try it out. We had 80+ temps a few days ago and now its only about 50 degrees. You can never get warm weather when you need it.

Yeah and freeze warning tonight for us!

 

[Innovate1]

370V is very close to max voltage a capacitor should see in normal service -- 240V is the RMS voltage, so the peak voltage is ~340V, and class B overvoltage of 8% pushes that to ~367. Increasing the voltage rating of the cap will almost certainly improve its lifespan.

Although your numbers do seem to line up that's not the reason for the 370V rating at all. The 370V cap rating is the RMS AC rating and has nothing to do with the peak of the incoming line voltage. 370VAC cap would be able to handle 523V peak and has some margin so actually a bit more. The real reason is the run winding cap typically has higher than line voltage. So 370 would be fine to replace 370 although a higher rating gives more margin.

 

[75gmck25]

Temps got up to about 93 degrees today. A/C kicked in and had no trouble pulling the house temp down. Looks like the new capacitor works fine.

 

[dscheidt]

Temps got up to about 93 degrees today. A/C kicked in and had no trouble pulling the house temp down. Looks like the new capacitor works fine.

Have you ordered the spare yet? (and one for the other, if you've got both start and run caps?)

 

[75gmck25]

The A/C was installed in 2013 and I didn't have an issue until 2026, so its track record has been excellent so far. Considering the time span I have to consider whether I would ever find the capacitor when I need it.

 

[Milton Shaw]

Having trouble finding something is a problem most of us are having. So get the new box, put it in a zip-lock and store it in the control area of the condenser outside where you will eventually need it. Stays dry and don't have to look for it again.

 

[Jeepster04]

I find it very interesting that banging on the fan caused it to start spinning and the issue was a bad capacitor. I'd keep an eye on that.

Anytime I've replaced a bad capacitor, I had to give the fan a good push to get it started spinning. I've manually started a fan for several days waiting for a capacitor to come in. That particular unit would run all afternoon/evening, so I only needed to start it one time a day once the sun was up and the house was hot.

 

[racecougar]

yeah mine was doing that before i swapped the hemi in. turned out the fan clutch was getting weak. could also be low on refrigerant which makes the compressor work harder. check your freon level first, way cheaper than replacing stuff. if that's good then the clutch is probably next

You're cooling your house with a Hemi?

 

[Codyboy]

You're cooling your house with a Hemi?

He thinks this is a jeep forum.