Engine bay noise with A/C running

[Ray500]

Hello guys,
My 2016 Limited 3.5 kept making the noise all summer with the AC on. I want to say it was louder on hotter day specially when first taking off in the car. The noise would never completely go away but got quieter as the car got driven or the cabin cooled down. I also notice that the noise gets louder when I turn the rear AC on. I talked to a friend of mine who is a very knowledgeable car tech and he seems to think it is the alternator making this noise. His theory is that on the initial startup with a somewhat discharged battery, the alternator has to work harder specially with the AC on. As the the alternator catches up, the noise gets better until the rear AC is turned on and the alternator gets a load on it again. I don't think I feel comfortable swapping parts for this issue as I would like to keep the factory installed parts on the vehicle until there is a proven failure. Changing compressor is never ideal because it can introduce contaminants in the AC system that may cause repeated AC issues. Hope this helps.

 

[Danny Mas]

Hello guys,
My 2016 Limited 3.5 kept making the noise all summer with the AC on. I want to say it was louder on hotter day specially when first taking off in the car. The noise would never completely go away but got quieter as the car got driven or the cabin cooled down. I also notice that the noise gets louder when I turn the rear AC on. I talked to a friend of mine who is a very knowledgeable car tech and he seems to think it is the alternator making this noise. His theory is that on the initial startup with a somewhat discharged battery, the alternator has to work harder specially with the AC on. As the the alternator catches up, the noise gets better until the rear AC is turned on and the alternator gets a load on it again. I don't think I feel comfortable swapping parts for this issue as I would like to keep the factory installed parts on the vehicle until there is a proven failure. Changing compressor is never ideal because it can introduce contaminants in the AC system that may cause repeated AC issues. Hope this helps.

Thanks for the input. I agree that mine does the same thing on hotter days and also from starting from a stop. The thing that stands out is that the sounds coincides directly with the rpms for some reason. As they get higher starting from the stop, the sounds gets louder and then drops. The battery just went bad about 2 weeks ago and it was replaced but the issue still continued with a new battery though. I’m going to check the rear ac to see if it gets louder too. Just picked up the vehicle yesterday from changing the compressor. Haven’t heard anything yet but it was also a cooler day. I’ll check today as warming up a bit but will be out of town till thanksgiving week

 

[Ray500]

Another thought is that our compressors could be "dual stage". Maybe that is why we experience louder whining when the weather is hotter or on the initial AC startup or when when rear air is turned on. I know some of the newer HVAC systems in homes work that way. Any thoughts?

 

[limited3.5]

its possible.
Rear vents I suspect may be on separate ac radiator (probably compressor has to work more) since I've seen ac piping in rear left side behind the bumper.

p.s. my 2017 is noisy as jet engine in the summer but it gets very hot here for 4 months.

 

[peterk9]

Just went through a hotter than normal Summer this year and I can't recall any unusual noise coming from the A/C or engine bay. In fact, it was hard to even tell that the A/C was running.

Peter

 

[Ray500]

Peter,
You must be one of the lucky ones! I am happy for you that you don't have to deal with this issue. I wonder if all the compressors across the whole line up are manufactured by the same company with the same specs.

 

[kam327]

Anyone have any updates on this? I'm noticing a whine... most noticeable after we've parked somewhere for an hour or more and then get back in and start driving. It's garage kept and I don't notice it when leaving the house... so this A/C compressor theory makes sense. The car stays cool in the garage and there's no whine when leaving the house. But the car gets hot after sitting out in a parking lot in the sun and the A/C compressor has to work harder to cool the cabin down. Or the compressor itself is hotter with the sun beating down on the black hood. At first I thought it was the alternator but thought it was strange there was no whine coming through the car's speakers like in older cars with bad alternators. And that it pretty much only happens when leaving a parking lot during the day.

 

[Danny Mas]

Anyone have any updates on this? I'm noticing a whine... most noticeable after we've parked somewhere for an hour or more and then get back in and start driving. It's garage kept and I don't notice it when leaving the house... so this A/C compressor theory makes sense. The car stays cool in the garage and there's no whine when leaving the house. But the car gets hot after sitting out in a parking lot in the sun and the A/C compressor has to work harder to cool the cabin down. Or the compressor itself is hotter with the sun beating down on the black hood. At first I thought it was the alternator but thought it was strange there was no whine coming through the car's speakers like in older cars with bad alternators. And that it pretty much only happens when leaving a parking lot during the day.

They changed my compressor out last year and still making the noise

 

[1fordtech1]

Years too late but might help others. I had an Explorer vehicle come in that had a growling noise from the AC when engaged, I believe it was around 2017 model. It sounded like the compressor was bad and we replaced the compressor and flushed the system. Customer returned with same issue months later. We knew it wasnt the compressor that soon so after lots of road tests and isolation we concluded that it was a pressure problem due to high pressure buildup only when under accelleration or at cruise speeds. Checked for fans failing but fans never stopped operating. Retrieved codes on the vehicle and found a code in the PCM for shutter control malfunction. After close examination we found that the upper shutters were staying closed while the lower shutters were changing position normally. This closed shutter condition was enough to cause high head pressures under load and causing the compressor to whine from the high head pressure. We replaced the damaged/defective shutter assembly and all was well, noise from compressor resolved. Sometimes the resolution is a little tricky to figure out, but a good lesson learned in the continuing journey as a technician.

 

[KennyPowers55]

Is there a way to check the shutters? I'm experiencing what I believe to be the same problem, but I'm not getting a code for shutters.

 

[TTIntercept0r]

Is there a way to check the shutters? I'm experiencing what I believe to be the same problem, but I'm not getting a code for shutters.

Mine does the same when first turned on, sounds like a supercharger whine between 2k and 3k rpm, goes away after that. And the whine totally goes away when using recirc. I want to say it only happens when using MaxAC, but cant confirm that either. I haven't done any testing.

Most likely we both have different issues. I don't have any codes either.