FIXED FAS257S2A 25,000 BTU Window AC unit diagnosis - capacitor or compressor?

cwatkin

Premium Member
Joined
Jul 23, 2017
Messages
41
Location
MO
Model Number
FAS257S2A
Brand
Frigidaire
Age
6-10 years
I have a Frigidaire 25,000 btu Window AC that decided to call it quits on the hottest day of the year. Luckily I have a spare although it is much smaller (another question on this forum).

Anyway, the 25,000 btu unit had been cooling fine but there was one symptom for the past year or so. It would intermittently trip the breaker either immediately when the compressor kicked on or within 3-5 seconds or so after it had started. I replaced the breaker and made sure all the wiring connections were good but nothing changed. It would sometimes trip the breaker twice in a day but then would have no issues for a month. There had been one breaker trip within a couple days of the thing calling it quits. The sticker on the side says it requires a 14 Amp service. The breaker it is on is rated at 20 Amps and the wiring rated at 30 Amps. I also have a nearly identical 25,000 BTU unit that is setup exactly the same in regards to the breaker, wiring, etc. and have had no problems with breaker trips.

So, a few days ago I noticed a loud electrical hum for a couple seconds and the lights dimmed. Then it happened again a few minutes later. The blower on the unit was running but the compressor was not. Then while I was standing there the hum happened again and it was definitely from the AC unit. It basically sounds like an electric motor that is locked up. It was definitely pulling some current as the lights dimmed each time this happened. I suspect this had been going on for some time as I found it when I got home but the breaker hadn't tripped.

Anyway, I talked to an HVAC guy and he said he suspects the compressor is shot based on my description. He said the compressor had probably been drawing a lot more current trying to overcome locking up for a while and causing the breaker trips. He said he thinks the unit is totally locked up and now the internal overload protection is tripping before the breaker has a chance to trip.

He is offered to test the capacitor for free if I got it out of the unit. I have it out and it is a 2 in one unit where one part starts the blower motor and the other the compressor. The capacitor shows no signs of distress which makes me wonder about the compressor. Usually caps are bulging or leaking when they fail but we will see. He says sometimes one side of the capacitor will fail before the other so that might be why the fan is working but not the compressor.

The unit is also 8-9 years old and he says that they aren't really made to last that long these days. If I can get a diagnosis of the capacitor being the issue for sure I would be willing to replace that. If not,, I would never consider putting money into have a new compressor installed in the thing. Any insights based on the symptoms I describe? Hopefully I will get an answer on the capacitor in the next couple days.

Since my other unit is identical or nearly identical I will keep any of the electronic boards, sensors, and controls as spares. I assume the blower motor is not a common failure so guess that wouldn't be worth keeping????

Thanks.
 

jeff1

Appliance Tech - Moderator
Staff member
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Messages
23,721
Location
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Hi,

FAS257S2A
I believe that is missing a digit or two.

Capacitor-5304459575--01394191.jpg LINK> Capacitor

[video=youtube_share;kdFIARakavk]https://youtu.be/kdFIARakavk[/video]

If the cap tests ok, the compressor is then suspect.

jeff.
 

cwatkin

Premium Member
Joined
Jul 23, 2017
Messages
41
Location
MO
Maybe this was a Lowes specific model. I know it came from Lowes and just looked it up and it showed up as a past product sold at Lowes. https://www.lowes.com/pd/Frigidaire-25000-BTU-1660-sq-ft-230-Volt-Window-Air-Conditioner/3043965

I did get with a neighbor who used to work with HVAC and the capacitor is toast. I did bring another capacitor I pulled out of some junk and it tested good and close to the specified capacitance. The capacitor from the unit was done for.

I looked at the AC again and found something else disturbing. The blue lead to the compressor was black and had apparently gotten really hot. The connection seemed solid but for some reason it was getting really hot. I am not expert but this doesn't seem to be a good sign. I am considering just sending this off as junk for safety reasons as well.
 

jeff1

Appliance Tech - Moderator
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Messages
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Location
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The blue lead to the compressor was black and had apparently gotten really hot.
Compressors can draw too much current and overheat things :(

jeff.
 

cwatkin

Premium Member
Joined
Jul 23, 2017
Messages
41
Location
MO
It is fixed for now!

It is working for now. I simply replaced the run capacitor and the compressor fired right up. I just left it sitting on the floor plugged in as I didn't want to lift the thing if this didn't work. The 40+8 mfd cap that came with it was around $100 and out of stock all over the place with no expectation of it coming in.

I found a lot of 40+7.5 mfd caps online so went to a local place. The local supply house had a 40+7.5 mfd capacitor so I got that one. The 7.5 is for the fan motor and it seems to fire right up and run fine on this. I was more concerned about having the compressor one correct as that was my issue from the start.

Conor
 

jeff1

Appliance Tech - Moderator
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Messages
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Location
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I was more concerned about having the compressor one correct as that was my issue from the start.
Yup, usually can go 5% either way when needed.

jeff.
 

cwatkin

Premium Member
Joined
Jul 23, 2017
Messages
41
Location
MO
I was wondering about replacing the cap in the other unit for good measure.

So far, so good. The unit seems to be working well and there haven't been any breaker trips yet.

I have another nearly identical unit that uses the same capacitor. This unit cools the bedroom area and is about the same age but probably has A LOT more hours on it. I bought another new cap to have it on hand in case that one fails but was wondering if I should go ahead and replace it on a unit that is 8-9 years old. My neighbor also has a tester so I could test it to see where it stands.

Any opinions? My main concern is because I have read about compressors getting cooked because of a failed capacitor.

Thanks,

Conor
 

jeff1

Appliance Tech - Moderator
Staff member
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Messages
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Old motto....if it works, leave it alone.
JMO!

jeff.
 

cwatkin

Premium Member
Joined
Jul 23, 2017
Messages
41
Location
MO
Yes, I understand that concept BUT...

I repair computers and other sensitive electronics for a living. Just because a power supply unit powers on a computer doesn't mean it is good. The voltages may be out of spec, damaging sensitive electronic components. I usually test power supplies on computers and suggest a replacement if the voltages are not within spec as have seen further damage and data loss occur due to power supply issues.

I suspect that run cap on the AC unit was out of spec for a year or more. It was starting and running the compressor just fine MOST of the time but it would trip the breaker sometimes. Then it quit completely and was hammering the overload relay repeatedly. I could tell that the wiring had been getting hot because it was drawing more current trying to start.

I know these compressors are not nearly as complex as the stuff I deal with but figure that a situation like this is going to heat up the windings and their insulation within the compressor motor which isn't good. I would rather replace a capacitor proactively rather than deal with a complete compressor failure down the road.
 

cwatkin

Premium Member
Joined
Jul 23, 2017
Messages
41
Location
MO
I wanted to give everyone an update to this thread. The window AC unit in question has continued to operate without any more compressor issues. It seems the run cap was the problem all along. About a month later my other unit started doing the same thing. It would hum like a locked up motor and trip the overload. Anyway, I pulled the cap out and replaced it with one of the same specs and the problem was solved. It seems that these things are made to fail after a certain time. All is well with both compressors for now.

Thanks,

Conor
 
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