Loud A/C noise

[rbloedow]

I am getting ready to take my car into the dealer soon - now that I have needed to use A/C in summer months, I have noticed a weird noise.

If I start the car with the A/C left on, I get a moderately loud wheen from under the front of the drivers side dash/hood. It's not so loud when the car is stationary, but when I start moving it gets louder.

I noticed that if I shut the A/C system down after this, the noise goes away. I then restart the A/C system after turning it off, it runs without issue and makes no noise.

It only happens at startup and when I initially start driving the car. Any ideas from you armchair mechanics?

[barry252]

I think I've noticed the same noise. It only occurs upon start up and within 5 minutes, it's gone. The noise changes frequency with speed, almost like tire noise. I'll pay closer attention to it over the next few days. I've had my volt for over 18 months now, and have just noticed it over the past week or so. I'll try NOT using the A/C and see wazzup. I'll wait until tomorrow for this, though.... It's supposed to hit 100 degrees here in Baltimore today. I'm not convinced that it's the A/C unit. The A/C works fine.

Volt 63

[Chevrolet Customer Svc]

@ rbloedow,

I definitely have not heard of an issue like this before. Do you have an appointment already set up with the dealer? Let us know if they are able to find out what is causing the noise.

[ShannonVolt]

Just used the comfort setting today because of the intense heat and I also heard a noise. Mine sounds like a dump truck traveling down the road with large knobie tires near me. I kept looking in my mirrors and did not see anything. Can't say for sure but it appears to be AC related. I installed a cabin filter recently as I'm beginning to wonder if its from that. Will keep my ears open and see if I can't duplicate the issue.

[ShannonVolt]

Hmmm wonder if it could be the battery cooling system making this noise? Is there an actual fan that's used to cool the battery?

[Brittt1]

Hmmm wonder if it could be the battery cooling system making this noise? Is there an actual fan that's used to cool the battery?

I mentioned in an earlier thread about my check engine light coming on earlier when it hit 105 degrees, onstar said it was the air flow sensor, when i stopped there was what souned like a helicopter under the hood. Im assuming the sensor is activating the fan and is malfunctioning, totally heat related i think.

[saghost]

Hmmm wonder if it could be the battery cooling system making this noise? Is there an actual fan that's used to cool the battery?

Yes, eventually. The battery has it's own liquid cooling loop (one of the two radiator fluid bottles on the front of the engine compartment - the one that newer cars and retrofitted cars have an anti-tamper bracket around,) and its own radiator (lower half of the forward most one, I believe.) There's an electric pump that moves the coolant, but if it gets hot enough while not moving, it can command the radiator fan on, just like the engine, the power electronics, or the A/C.

(The battery can also use a chiller driven by the cabin A/C circuit to cool itself when it's feeling toasty and it's warm out, and a 1.8kW electric heater to warm its toes on a cold night. It lives a nice life really, coddled and protected from everything, unlike most of its kin (Leaf has no thermal management at all...))

[George S. Bower]

Yes, eventually. The battery has it's own liquid cooling loop (one of the two radiator fluid bottles on the front of the engine compartment - the one that newer cars and retrofitted cars have an anti-tamper bracket around,) and its own radiator (lower half of the forward most one, I believe.) There's an electric pump that moves the coolant, but if it gets hot enough while not moving, it can command the radiator fan on, just like the engine, the power electronics, or the A/C.

(The battery can also use a chiller driven by the cabin A/C circuit to cool itself when it's feeling toasty and it's warm out, and a 1.8kW electric heater to warm its toes on a cold night. It lives a nice life really, coddled and protected from everything, unlike most of its kin (Leaf has no thermal management at all...))

Walter,
Has anyone run any tests to find out how much energy it takes to cool the battery when your charging it and it is running the chiller to coool the battery??

For example : It's 95 F OAT now and if I charge the battery now esp. after a trip in the heat what would that drop my Charging efficency to. Seem like the EPA sticker had the charger at 85%.

Is it a big enough difference I would just charge in the AM when it's cool.

[saghost]

Walter,
Has anyone run any tests to find out how much energy it takes to cool the battery when your charging it and it is running the chiller to coool the battery??

For example : It's 95 F OAT now and if I charge the battery now esp. after a trip in the heat what would that drop my Charging efficency to. Seem like the EPA sticker had the charger at 85%.

Is it a big enough difference I would just charge in the AM when it's cool.

I'm not aware of any test data like that. Solar Dave has a few charts from his TED about how the car hits the grid for TMS power when it's fully charged, but that's a little different.

I'm not sure how easy it'd be to get, either - largely because I suspect it's a variable amount - not 200W for the length of the charge, but 1kW here and 0W extra there. I suppose if you logged into DashDAQ a series of charge cycles with and without TMS, you could look at peak or average flow into the battery and use that to infer TMS power usage...