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Discussion Starter · #1 ·
I've noticed this several times in the summer, only when it's above 90º. They'll be a very loud whine from the engine bay... it's very obvious when stopped, and it's still quite noticeable at moderate speeds, though very faint on highway due to other noise. I'm guessing it's the compressor running overtime in the heat (usually goes away immediately if I turn off a/c), but it's just so loud that I always think something is wrong. The a/c works fine, the air is very cold. But it also works fine when it's 80º out without the loud whine.

I haven't tried popping the hood to try to locate the noise because I figured the ICE would just come on and further mask the noise source... logically it's either the compressor in some sort of high mode, or possibly the radiator fans on turbo. Just wondering if other gen1s hear anything like this in extreme temps... perhaps it's normal and we're just spoiled by a normally very quiet car. No error codes, and a/c performance seem fine, I'm just worried one of those parts is dying or something.
 

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I'm sure someone more knowledgable will come along and sort this out by correcting me, but I'm fairly certain* the sound you hear is just the Battery Temperature Management System doing its job, which in this case is probably cooling the battery down by cycling the coolant system.

*I hear this sound almost every day now when I get home and plug-in, since here in Texas we've been dealing with triple digit days so this is the most logical explanation I've been able to come up with based on my personal experience.
 

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Same here with the sound.
So far it seems that it has to be +85 degrees for it to happen and I have to agree that it "feels" pretty loud, but again that sort of thing is pretty relative with a Volt. I thought it was terribly loud and then a RAM diesel pulled up next to me at the red light and I couldn't hear it any more :O
 

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I hear the same thing and have wondered if things were OK. I have nothing to feed my worry other than the sound. For sure it is on the hottest days, usually 95+ at which time I will be running the cab AC also. By watching the MyGreenVolt app, I am certain it is cooling the batteries when the sound cranks up, as I can see the power draw on the battery pack double when the sound cranks up, and the battery temperature starts dropping. When the batteries get into the 70's, sound stops, power draw drops. The sound just seems too loud to me, but maybe this is from driving a normally quiet car? I asked my brother if he has heard the same in his Volt (same year) and he said no, but maybe he just didn't notice it? If I could get a ride in it on a hot day, I could tell for sure.

A little hard to describe the sound as, it might be fans, but if it is, it is like a fan with a bearing going out, as it has a bit of a rasp to it. Like the OP, I was guessing the compressor too.
 

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Discussion Starter · #6 ·
Thanks, guys, good to hear it's normal. I only hear it a few times a year when it gets to 90º+ here, so it always shocks me. The a/c noise is not noticeable to me at all at lower temps. Dutch is right that it's still quieter than a diesel pickup ;)
 

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I thought my 2015 volt was loud on max. My ELR on max will put a diesel truck engine to shame. Sounds like a jet engine sometimes at full duty and the fan can be loud too. As loud or louder than a car engine on startup after a hot day baking in the sun. It goes away after a minute or two and quiets down.
 

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I was surprised that they didn't quiet the compressor whine in the Gen 2. I had it in my '13 when it was very hot -- usually when you had TMS running also on a hot day. Thought something was wrong at first, but realized it was the A/C. It's equally loud in the Gen 2, but fortunately it doesn't last very long.
 

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Same here with the sound.
So far it seems that it has to be +85 degrees for it to happen and I have to agree that it "feels" pretty loud, but again that sort of thing is pretty relative with a Volt. I thought it was terribly loud and then a RAM diesel pulled up next to me at the red light and I couldn't hear it any more :O
heh. Plus the part where our Volts take about three days to actually completely turn off... There's a bit of an adjustment to both how quiet AND how often they do make what noise they make.
 

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2012 56K miles - live in hot summer Oklahoma. My garage is over 100 degrees F regularly when temps are in the 90's outside (like today). I had the same crazy sound develop so gradually over the 3 years of owning this car when charging and especially after charging was completed. I just thought to myself - Well, there aren't any CEL's or vehicle messages, it must just be the way it's designed: When it's hot, the TMS just screams. My concern was, like OP, that something was being damaged. Anyway, I eventually got a CEL for a code P0534, basically the battery not being cooled sufficiently. The culprit was my freon charge being low. After a recharge, the sound I'd been having before completely went away. Now, when the TMS is working, it's a very subdued whirring sound, the crazy whine/screaming is gone. Today, the TMS ran for about 15 minutes after charging was complete in my 100 degree garage, then it was done. Before, it could run for hours (hindsight, obviously because of the low refrigerant charge)

TLDR: check your freon charge!
 

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Thanks, guys, good to hear it's normal. I only hear it a few times a year when it gets to 90º+ here, so it always shocks me....
During summer months here in Phoenix we're lucky to see overnight *lows* below 90º, and daytime highs are routinely above 105º so I'm quite familiar with the sound you describe. It is impressively loud, especially compared to the Volt's 'silent running' in cooler weather. Much louder than the ICE.
 

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....I eventually got a CEL for a code P0534, basically the battery not being cooled sufficiently. The culprit was my freon charge being low. After a recharge, the sound I'd been having before completely went away.....
Interesting. Before the freon recharge, was it hard to cool the cabin down with a/c?
 

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Interesting. Before the freon recharge, was it hard to cool the cabin down with a/c?
Strangely enough, no, not at all. I never had any issues with the cabin AC, was always ice cold. That's why the low freon charge was never on my radar. What I learned is that it's possible for the Volt's freon charge to be low enough to make the TMS scream like crazy and work way too hard and not throw any codes while still cooling the cabin perfectly. But, eventually the car's protection programming kicks in and will give a CEL. From now on, I'm going to make a habit of having the freon charge checked periodically.
 

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2012 56K miles - live in hot summer Oklahoma. My garage is over 100 degrees F regularly when temps are in the 90's outside (like today). I had the same crazy sound develop so gradually over the 3 years of owning this car when charging and especially after charging was completed. I just thought to myself - Well, there aren't any CEL's or vehicle messages, it must just be the way it's designed: When it's hot, the TMS just screams. My concern was, like OP, that something was being damaged. Anyway, I eventually got a CEL for a code P0534, basically the battery not being cooled sufficiently. The culprit was my freon charge being low. After a recharge, the sound I'd been having before completely went away. Now, when the TMS is working, it's a very subdued whirring sound, the crazy whine/screaming is gone. Today, the TMS ran for about 15 minutes after charging was complete in my 100 degree garage, then it was done. Before, it could run for hours (hindsight, obviously because of the low refrigerant charge)

TLDR: check your freon charge!
This was my suspicion, that refrigerant might be low in coolant system. Thanks very much for this post.
 

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Last night I added some refrigerant to the Volt AC system.

Today I tested.
The day was not as hot as many this summer (up to 86 Deg F) today. During the day the Volt was sitting in the sun green housing. When I started the car the battery pack was around 78 Deg F (info from mygreenvolt app) So I ran the vehicle super hard by running up some really big hills with the car floored, until the battery temp exceeded around 88 Deg F, then it began to fall as the Volt started cooling the batteries. I stopped, turned on the cab AC to several different settings including settings where in the past I heard "the noise" The sounds were significantly lower. I am still not sure if there isn't a cooling panic mode, if things are super hot. So I will test some more when temperatures are higher (assuming I get that chance as Sept. starts tomorrow).
 

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Did you hook up gauges and note pressure? purge and refill or just dump in refrigerant and ball park it?
In this case I noted the pressure at the current temperature, it looked a bit low, so I added a little, about 6 oz refrigerant (pure refrigerant, no oil, no leak stop, no dye) to do a ballpark test. The capacity chart I found listed it as 32 oz for the refrigerant capacity. If others here report similar results, and I can confirm this is better on an even hotter day, I may go the full 9, or just take it in.

One note, the compressor oil for the Volt was listed as a hybrid oil, and as I understand it this is the only oil you want to use. To anyone thinking about this, I wouldn't stray from the recommended oil because the compressor is a 360 V compressor.
 
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