A/C issue

Admittedly I'm not having a computer cooling issue but it is an A/C cooling issue and I think the experts here can help. Two to three weeks ago my A/C unit tried to commit suicide by jumping out a second floor window. It landed in the bushes and was seriously warped. I was sure it was dead but I looked it over and I couldn't see any damage to any of the copper tubing, compressor looked ok too but I didn't have any tools to really test it. I managed to bend the metal framing back into shape and then plugged it in outside and it still worked so I put it back in the window. Its noisy, I can clearly hear some of the semi-snapped off plastic parts rattling, but it runs and it cools. Two days ago I noticed that it now sometimes makes a high pitched whine/whistle. It starts off very high and then goes down in pitch but is still high. The noise only lasts for a second or two and doesn't happen often. So, any phase-change gurus wanna gimmie an idea of what that might be and what I should do about it? I will answer any questions I can to give a better idea of whats happening to it.

Just a couple questions.
1) Were there any strange smells coming from the unit after it was dropped or after it makes those noises?
2) Is it really still cooling? On many models there is a quick way to open part of the front panel to get at a filter. Open that, remove the filter and touch/take the temperature of the coil.

I've only been working as an HVAC tech for a month but I've been surprised at the number of people who call us because their AC isnt working very well when in fact it isnt working at all.

1) No strange smells, and I checked. Didn't know what I'd do if I found any but I did give it a good sniff to check both when it happened and recently.

2) I touch the rad/coil on the front and it is cold. And it is still pumping out cold air.

I'm just worried about the sound. I've heard it twice, the first time much louder than the second time (which was barely audiable). My wife said she heard it the day before but didn't have a reference if it was louder than the ones we heard together. She thought it was coming from something outside but to me it clearly came from the air conditioner. It sounded like a pneumatic air piston releasing it's pent-up steam. I don't care too much about the rattling of the plastic parts as they vibrate. I already bolted two pieces together because they would no longer fit after the damage was done, and I'll do it to other parts if I continue to have rattle noise issues, that's just body work and it's not like I'm showing it off. But I am concerned about what it means by the high pitched whistling.

I'm not an HVAC guy or anything but I've done my share of refrigeration cooling. Not sure what would be making a high pitched sound... I think you should open the unit up, probably not too many screws and have a look inside. If some fan blades are broken, might as well epoxy them (if theres a chance) back together to cut down on vibration. The compressor I would think could have possibly been damaged but if you're still getting cool air then it's probably fine. Try and see where the whine is coming from, maybe you could run the AC on a table with the cover off with the fan wire unplugged and listen to it.

The sound you've described sounds like the opposite of the sound I get when I put test gauges on an AC (starts out low and gets high as it comes up to pressure), kinda like a whistle but "brassy".

[Wild *** guess] With that idea you may be getting that sound because oil/sludge has made it from the compressor to the metering device and is causing a blockage until the compressor can create enough pressure in the condensor to blow it though.[/Wild *** guess]

Since I dont believe many window AC units have valves for test guages you might be able to check for anything weird by testing the amp draw of the compressor. I believe the amperage should rise any time the compressor has to work harder or fall any time the work gets easier.

Is the unit cooling only or a heatpump? A heatpump will make noise either on startup or shutdown depending on the reversing valve action. The reversing valve switches the refrigerant path between heating & cooling modes.

Ben333 said:

I'm not an HVAC guy or anything but I've done my share of refrigeration cooling. Not sure what would be making a high pitched sound... I think you should open the unit up, probably not too many screws and have a look inside. If some fan blades are broken, might as well epoxy them (if theres a chance) back together to cut down on vibration. The compressor I would think could have possibly been damaged but if you're still getting cool air then it's probably fine. Try and see where the whine is coming from, maybe you could run the AC on a table with the cover off with the fan wire unplugged and listen to it.

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It's one of the ones where you can just undo a few screws and the guts will slide out of the outer framework, and that's how I tested it after it first dropped. One corner of the bottom metal plate that supports the guts was bent up and I forced it back down so the guts could slide in and out of the outer shell with ease. It's still a little bent, so is the outer shell, so those are some of the reasons for physical rattling that I don't really care too much about. If that gets to be too annoying I'll just bend it a bit more and pad it with foam. The fan is fine. Impeller shaft is straight, no damage at all in the fan blades. The base holding the guts is metal but the ducting that shapes and directs the airflow throughout the unit is plastic, and several of those pieces snapped their various "clips" that attach them together. I've used a nut and bolt to fix some, but again that's not my concern. That's like having a dent in the car door, I'm just trying to figure out if the engine is still good and if not what can I do about it. I would run the unit without the shell in the back yard to figure out where the noise is coming from but so far it has only happened three times. So I'd probably be out there all day for several days. But if the noise becomes more frequent, like every couple of hours, then I will follow that advice and see what I can see.

Shuruga2 said:

The sound you've described sounds like the opposite of the sound I get when I put test gauges on an AC (starts out low and gets high as it comes up to pressure), kinda like a whistle but "brassy".

[Wild *** guess] With that idea you may be getting that sound because oil/sludge has made it from the compressor to the metering device and is causing a blockage until the compressor can create enough pressure in the condensor to blow it though.[/Wild *** guess]

Since I dont believe many window AC units have valves for test guages you might be able to check for anything weird by testing the amp draw of the compressor. I believe the amperage should rise any time the compressor has to work harder or fall any time the work gets easier.

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That's a good idea. I'll give it a check with my multi-meter later today and let you know what I find.

JLK03F150 said:

Is the unit cooling only or a heatpump? A heatpump will make noise either on startup or shutdown depending on the reversing valve action. The reversing valve switches the refrigerant path between heating & cooling modes.

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Cooling only.

it kinda sounds like it could be the internal pressure release. when the head pressure gets to high it will release the pressure internally to the other side. this can happen when condenser fan stops working and temps get to high.

is the unit blowing out hot air as well, outside i mean?

Shuruga2 said:

I've only been working as an HVAC tech for a month but I've been surprised at the number of people who call us because their AC isnt working very well when in fact it isnt working at all.

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hahaha, no kidding i was talking to my boss and he was at a friends house when he said his ac stopped working all of a sudden. he check it out and it was never wired up! they had some serious wiring issues about 5 years ago and the jackass electrician didn't hook the power back up to the ac unit. so they thought that had working ac for over 5 years... wow.

I've got to get up on the ladder when it's running for a while to check if it's hot at the back. I'm assuming it is as it definitely is pumping out cool air on the inside. It hasn't really lost functionality, yet, and hopefully it isn't slowly self destructing. Which is what I'm trying to ascertain about the whistle sound. There is a switch to either recirculate the air internally or to draw it in from outside. Not sure if that's of any relevance but just letting you know in case it is. I've had it in both positions since the accident. Not sure what setting it was on when the whistling happened but I think it might have been "draw air in from outside" mode. It is too craptacular of a day here for me to dig the ladder out and go see what the back side is doing thermal wise. I'll hopefully get to it tomorrow and let you know.

while i've never heard one whistle before, it could be a capacitor for the compressor or fan. have a look at it, they next time you take it apart and make sure its not bulged or deformed in anyway.

Probably time to turn down the OC on the compressor


Noise wise, given that it had a large impact i suspect a bearing. Not that i'm a HVAC guy, closest to that i've done is replumbing a swamp cooler.