The intermittent A/C noise on the highway - I timed it, looks intentional

[Flot]

This topic comes up every so often - the intermittent "wind leak" noise you hear on the highway. After some testing, It looks to me like this is functioning as designed when the A/C system is running in recirc mode.

I had a 3 hour road trip and timed it, here were my findings:

- Noise is most apparent over 70 mph. It likely happens all the time, just that if you're going under 60 mph, you don't hear it
- The noise appears to be the recirc / fresh air door opening (possibly partially) for exactly 50 seconds
- This cycle repeats itself every 15 minutes 10 seconds
- Hitting the recirc button twice cancels the sequence and re-closes the door

I didn't get into testing if this happens on the first 15 minutes the system is active, or it is something that pops up after x minutes of the system running.

I assume this is a "introduce fresh air into the cabin" functionality when the system is set to recirc for a long time. Also not sure if doing the fresh/recirc button trick resets the timer in any different way. But on my drive, I clearly saw the sequence repeat identically at least 5-6 times. (I had to pay attention to driving at least some of the time)

 

[tobyw]

This topic comes up every so often - the intermittent "wind leak" noise you hear on the highway. After some testing, It looks to me like this is functioning as designed when the automatic A/C system is running in recirc mode.

I had a 3 hour road trip and timed it, here were my findings:

- Noise is most apparent over 70 mph. It likely happens all the time, just that if you're going under 60 mph, you don't hear it
- The noise appears to be the recirc / fresh air door opening (possibly partially) for exactly 50 seconds
- This cycle repeats itself every 15 minutes 10 seconds
- Hitting the recirc button twice cancels the sequence and re-closes the door

I didn't get into testing if this happens on the first 15 minutes the system is active, or it is something that pops up after x minutes of the system running.

I assume this is a "introduce fresh air into the cabin" functionality when the system is set to recirc for a long time. Also not sure if doing the fresh/recirc button trick resets the timer in any different way. But on my drive, I clearly saw the sequence repeat identically at least 5-6 times. (I had to pay attention to driving at least some of the time)

We just picked up our 2019 on Saturday and then took about a 5-hour road trip yesterday, and I noticed this happening as well? However my HVAC wasn't in the auto mode... Sounded like a Hoover vacuum for a few seconds every once in a while and then back to typical road/cabin noise. So are we thinking this is, in fact, normal?

 

[Flot]

We just picked up our 2019 on Saturday and then took about a 5-hour road trip yesterday, and I noticed this happening as well? However my HVAC wasn't in the auto mode... Sounded like a Hoover vacuum for a few seconds every once in a while and then back to typical road/cabin noise. So are we thinking this is, in fact, normal?

Sorry, let me clarify - I have the 12" screen and the fully automatic temperature controls, but my system was still in normal choose-a-temperature mode, not "auto" mode selected.

I think this is normal. The fact that it happens 4 times an hour for exactly the same length of time makes me think it's part of the A/C Programming. I've had other cars with similar functionality where the manual mentions that even in recirc mode, it will occasionally open to let fresh air in. When I was below 60 mph, the noise was hardly noticeable, so I suspect it happens all the time and you just don't hear it.

I also noticed it on my road trip home (a year ago) in the brand new truck - although I certainly didn't realize it happened 40 times in the 10 hour trip. I think crosswinds etc can make a big difference in what you hear.

 

[I Love Grits]

I don't think its intentional. I usually drive around in recirc mode & have noticed the same timing as you, but the other day I was not in recirc and noticed the door still cycling itself every 15 minutes. Try it on yours next road trip and see if you can duplicate.

 

[Flot]

I don't think its intentional. I usually drive around in recirc mode & have noticed the same timing as you, but the other day I was not in recirc and noticed the door still cycling itself every 15 minutes. Try it on yours next road trip and see if you can duplicate.

So in fresh air mode, the door shifted to recirc (and it got quiet) for 50 seconds?

I don’t see how it couldn’t be by design. The timing is too precise. If it was for a random amount of time on a random cadence it’s be different. But once I timed it and paid attention it was dead on schedule, 15:10 and 00:50.

The thing I couldn’t tell was whether the door was opening 100% or if it was halfway open that might explain some of the extra noise.

 

[Cannonball]

Mine is doing this as well. The air is redirected when this happens because the dash vents lose flow and coolness until the sound goes away then airflow returns. I run it on upper vents, recirc, and set temp to low always.

 

[392DCGC]

There is no way this is normal. How many vehicles have you had in the past that have done this? If you're like me, the answer is zero. And oh by the way, my December 2018 built truck I currently have does NOT do this. But the May 2018 truck that I used to have did do this.

 

[JJRamTX]

So in fresh air mode, the door shifted to recirc (and it got quiet) for 50 seconds?

I don’t see how it couldn’t be by design. The timing is too precise. If it was for a random amount of time on a random cadence it’s be different. But once I timed it and paid attention it was dead on schedule, 15:10 and 00:50.

The thing I couldn’t tell was whether the door was opening 100% or if it was halfway open that might explain some of the extra noise.

It sounds like it was engineered this way to allow fresh oxygen into the cabin. The redesign is so much more air tight than the older designs that they had to allow for this, which also explains the flaps in the rear wall part of the cab also.

 

[I Love Grits]

So in fresh air mode, the door shifted to recirc (and it got quiet) for 50 seconds?

I don’t see how it couldn’t be by design. The timing is too precise. If it was for a random amount of time on a random cadence it’s be different. But once I timed it and paid attention it was dead on schedule, 15:10 and 00:50.

The thing I couldn’t tell was whether the door was opening 100% or if it was halfway open that might explain some of the extra noise.

Nope, the door shifted to halfway open - just like it does when in recirc mode. So it goes from full outside fresh air to half fresh/half recirc. Next time you're in recirc and it goes at 15 minutes, push the recirc button only once (turning off recirc). The door will finish opening (going to full fresh air) and the noise will be quieter that it just was & you'll be able to smell the outside air. That's why I think its opening halfway.

It sounds like it was engineered this way to allow fresh oxygen into the cabin. The redesign is so much more air tight than the older designs that they had to allow for this, which also explains the flaps in the rear wall part of the cab also.

Cabin flaps are not unique to Ram. They exist to allow air to escape when shutting doors so there's not a pressure wave felt in the cabin. My opinion is the two are independent.

 

[Rampat]

Mine does this too. I asked my dealer about it and the service department took it in to check the recirc door to make sure it was opening and closing properly and would replace if needed. After checks it was working fine and not damaged in any way. It just is what it is.