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I've seen a wide range of posts related to this topic, which makes it really difficult to narrow down relevant information that is applicable to my case. I'm hoping to get a more definitive answer by posting here, because the noise is getting out of hand. Here are the details:

Vehicle
Honda Clarity 2018 PHEV Non-Touring

What type of noise?
A loud, consistent whirring (presumably from the two condenser cooling fans).

When does it occur?
Basically anytime the A/C is turned on and active (does not occur when air flow is on and A/C is off, etc.); also, not sure whether it's related or not, but I believe when the gas engine kicks on (i.e., lithium ion battery is depleted) the noise level has also gotten notably louder.

How loud is it?
Loud enough that I can't park at the curb in a residential at night and have the A/C running unless I want to receive complaints about keeping people up.

What has been done about it?
At first I took it to the dealership to get it diagnosed. Long story short, they took my car to the back and had me wait all day in a crammed packed waiting area for an entire day, then charged me a $75 "diagnostics fee" despite "not being able to determine any cause", only for me to drive back home that evening to discover they never even popped the hood.

I've tentatively tried a few things on my own, such as applying some nano-tape/kinetically insulating materials in places I felt could vibrate — or amplify/exacerbate them — such as the areas where (not sure what the correct vernacular terms are here) the condenser assembly is seated/bolted onto the chassis. I've also gone through and made sure all bolts were tightened. I tried cleaning the fans themselves, but very little was actually accessible to me as I didn't want to disassemble or damage anything without being certain I knew what I was doing. I've also conditioned the rubber gaskets with petroleum jelly or silicone lubricant on a regular basis, and added a rubber "lip" to the hood which keeps it pretty well sealed when closed.

I'm unsure which of the above had the most effect, but the steps did appear to abate the noise level for a while. Unfortunately, over time the noise has increasingly gotten to a point where it's no longer tolerable once again.

What I'd like to find out?
If possible, I'd like to know the root cause for this and — hopefully — do something to address it. If at all possible, I'd like to not be told that the only thing to do is to replace it altogether, especially not by someone who cannot even state with any specificity what is wrong with the assembly to begin with that's causing the noise.

UPDATE 1

I'm only on the first step and I'm already stumped, not off to a good start!

fan connectors

So as you can see, each fan appears to have two connectors, not just one. I managed to unplug one of them, but can't seem to figure out how to unplug the other type of connector. As you can see, it's pretty cramped in there so it's hard to get a good look, but it appears to me the white part should somehow be able to disengage and allow the remaining portion of the plug to come out, but I can't be sure. FYI, when I started the car with just the other connector unplugged, both fans continued to run, and I received a notification on the dash stating that Adaptive Cruise Control had been disabled.

Any tips on how to disconnect the larger looking cable? Thanks!

UPDATE 2

So actually, after spending some time peeking around under the hood, I've come to notice there's no need to test the fans individually, it's very audibly distinct that the noisier side is the passenger side fan (but that isn't to say that they can't both still be noisier than the norm, only that one is definitively more so than the other). I've taken a video, by the way, just for reference here.

I tried applying pressure to the center of the fans, and while the fans themselves did not have any give or radial movement in respect to their enclosures, I did note that the entire assembly itself did have up to about half an inch to an inch of radial movement in respect to the chassis. However, I don't believe this to be the cause (or it isn't readily apparent if it is), as when I had the fans running there wasn't any significant vibratory or auditory feedback originating from the contact points (I'd already applied rubber tape to them prior anyway). There was no contact between the blades and the enclosures that I could detect, but I did note that there was a greater sensation of kinetic friction (or viscosity?) on the passenger side fan in comparison, and this was noted prior to me noticing the noise level being higher on that side, so I don't believe I was biased.

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  • Have you tried disconnecting one fan at a time to see which one is making the noise?
    – HandyHowie
    Jul 12, 2023 at 12:29
  • This is only a guess, but I think you'll separate that connector by first sliding the white piece toward the right (all directions per the photo, not per the real world). Not to take the white piece off, just to move it till you feel resistance. There's a slot toward the right where you can insert a screwdriver blade against the white tab coming toward the camera, and twist the screwdriver to get the movement started. Once that piece is moved right there should be a tab on the photo-bottom side between the 2 green cylinders. Push hard on the tab, wiggle connector, it should come out.
    – MTA
    Jul 15, 2023 at 1:23
  • I'm a little confused by "the entire assembly itself did have up to about half an inch to an inch of radial movement in respect to the chassis." If you can slowly and very carefully cause this movement while the fan is running and the noise does not change, and you're sure that the fan blades are not rubbing on anything, then that's a pretty strong indication that one or both bearings in the fan motor on the passenger side fan are shot. If that's the case, replacing that fan motor only should fix your problem.
    – MTA
    Jul 15, 2023 at 1:29

3 Answers 3

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Arctiic, with your permission I’d like to give you a dose of tough love to try and get this repair moving forward. I want to help you, I really do, so please bear with me and keep an open mind as I take you through this. There are some very smart, experienced mechanics here who can help you if you will only help yourself.

You’ve given us almost nothing to work with, but you want the root cause of a problem that you’ve been told by a dealer can be fixed by replacing the fans. You’re afraid to start taking things apart on your own due to your limited experience – I get it, you’re being appropriately cautious – but what do you expect to achieve by learning the root cause if you’re not prepared to tinker? That approach has only cost you $75 and a full wasted day so far, so don’t make that mistake again.

Listen, most independent mechanics and all dealers are not interested in the root cause of something like this that can be fixed easily by replacing an assembly because they’re not going to take, say, a fan motor apart and replace a bearing inside the motor if that’s what’s wrong. The labor (shop hours) to perform a repair like that, including time to source parts that are not normally supplied to dealers, would exceed the cost of a whole new assembly. Beyond that, you probably won’t find a mechanic to do root-cause repair work like that because that would put him or her on the hook for further repairs if the part fails again.

Learning the root cause is only useful if you’re going to repair it yourself without involving a shop and if you’re prepared and equipped to disassemble and repair sub-parts that in today’s world are always replaced as a complete assembly. Based on what you’ve said so far, I don’t think you’re prepared or equipped to do that.

I’d also like to point out that your question is getting little attention here because it’s so off-putting. The only useful fact that we’ve gotten from all that text, as well-stated as it is, is that one or more of your A/C or radiator fans is really, really, incredibly noisy. The rest is a rant. It’s not useful to tell us that the dealer treats customers like livestock. We already know that, which is why most of us here who answer questions stay away from dealerships except for recalls and warranty work.

You complain about paying for diagnostic time? There ain’t no such thing as a free lunch, bub. A professional mechanic reading your question is likely offended by that attitude and won’t spend any further time on your problem.

OK, I’m finished with the tough love. Let’s pay some attention to your noisy fan or fans.

First, stop using petroleum jelly on rubber parts. It degrades rubber. Silicone grease or silicone oil is OK.

Handy Howie suggested that you try unplugging the fans one at a time to see if the noise is coming from one or both fans. If you can figure out how to unplug them, that’s an excellent idea. You may have to push this and pull that to disconnect the connector.

Spin the fan blades and make sure they are not contacting the housing as Old Fossil said. While you’re at it, check that there are no missing blades. There should be no sticking, catching or a gritty feel as you turn the blades.

Grab the hub in the center of the fan blades and see if you can force the motor + fan assembly radially in any direction such that a blade contacts the housing or such that the entire assembly moves a significant distance. This is to test the rubber mounts for wear or damage.

Now for a delicate test: see if the blade, its hub and the motor shaft will all move in, out or radially as a unit while you hold the motor itself perfectly still. There should be no movement of the shaft relative to the motor at all. You’re trying to detect a worn outer bearing. (There’s no way to test the inner bearing without disassembly of the fan motor.)

If you find something broken or worn and you want to replace it yourself, you’ll have to get the old one off. That might involve moving the radiator or other parts. If you want step by step instructions, you can get a short term subscription to an online repair manual such as AllDataDIY.com.

Please let us know if you find something amiss and need further input, or if you have further details to add.

NOTE: Although I’ve criticized your approach to this repair, I’ve been careful not to make anything here seem like a personal attack and I’ve kept the wording respectful even though it’s frank. If you feel offended or you feel that this answer is not helpful and it galls you to see these words online, just leave a brief comment on this answer and I’ll be happy to delete it.

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    I appreciate your candor, and I can see where you're coming from. The root cause paradigm I have is a relic from my previous profession (I was an industrial food safety specialist for ten years). While I can follow your logic in regards to cost-to-benefits considerations, I'm resigned to stepping on some toes as old habits die hard. This reminds me of an old pet peeve of mine: IT technicians power cycling a router to "fix" network issues. To me, if you cannot define the root cause, you might still be able to apply a corrective action, but there certainly won't be preventative actions..
    – Arctiic
    Jul 12, 2023 at 23:34
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    or validation. If you don't understand why the router being power cycled abates the symptoms (forces DHCP to terminate leases, flushes DNS cache, and then renews client IP leases), then you're basically resigning yourself to repeating that same "fix" every single time the same issue is repeatedly encountered. Well, I understand the reality is most IT technicians aren't paid enough to care beyond just hitting the reset button and moving on to the next job, but I digress. Regarding the dealership, there's a couple of things you may have misunderstood (or I may have just relayed ...
    – Arctiic
    Jul 12, 2023 at 23:34
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    poorly). First, they did not offer to replace just the fan assembly, they were referring to the entire condenser unit assembly, which was at that time quoted to me as upwards of $3,000+ out the door. Secondly, I have zero complaints about paying for services rendered, provided that services were actually rendered. They told me that they had removed and examined the assembly, but could not determine any specific cause; when I got home that evening and popped the hood to take a look for myself, I saw that the layer of dirt/dust present was wholly and uniformly intact. In..
    – Arctiic
    Jul 12, 2023 at 23:35
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    other words, I meant it quite literally when I stated that they just drove my car into the service bay, went back to all their other jobs, then at the end of the day pulled my car back out to the front and slapped me with a $75 bill. The cause "couldn't be determined" because no one ever looked; and with your explanation, I'm now understanding they essentially have no monetary incentive to do anything if it isn't just swapping the entire thing out for another one.
    – Arctiic
    Jul 12, 2023 at 23:35
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    Thank you for the additional diagnostics procedural steps for me to try, I will report back once I've completed them or found anything additional. No need to remove your post, in my opinion everything you stated was logically sound and constructive.
    – Arctiic
    Jul 12, 2023 at 23:41
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It sounds like normal operation to me. For example when the A/C kicks in the fans activate. In any A/C system the compression of refrigerant generates heat and the condenser core (the aluminum radiator) needs to cool down to keep it within a specific temperature range for optimum operation efficiency.

Similarly when the internal combustion engine operates it too generates heat and needs cooling. In internal combustion engines the ambient noise is higher compared to a electric or hybrid vehicle which is for the most part much quieter by comparison. As a result the cooling fans sounds are more noticeable.

Whether or not it the noise would disturb the neighbors is debatable since sound intensity diminishes by inverse square law. For example If at a certain distance a sound is perceived at a given intensity, at 10X the distance the same sound is perceived at 1/100 of that intensity. Local ambient noise such as heat pumps,other cars etc would also mask the noise.

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  • I can assure you that it is nowhere near "normal operation" level of noise, and that the disturbance is not open to debate. When I go pick up my wife, I never have to call or text her to let her know I'm outside, because my car tells her (and all the neighbors) for me. The dealer's service manager agreed the noise was well out of the norm, but only pushed to get the entire assembly replaced at our cost and didn't care otherwise. I can't even park on my own driveway without my landlord coming out to tell me to shut my car off because it's drowning out his TV.
    – Arctiic
    Jul 12, 2023 at 4:11
  • Perhaps inspect the fan itself .maybe a fan blade is coming in contact with the shroud assembly.. If so use a small round file to file away any contact point until the fan is moving free.. For further dampening effect use small rubber washers at the points where the shroud contacts the car body..Avoid dealerships like the plague.
    – Old_Fossil
    Jul 12, 2023 at 4:48
  • Just rereading your answer and thought I'd ask for clarity, when you say "local ambient noise", you mean local in respect to the listener, and not the source, correct?
    – Arctiic
    Jul 14, 2023 at 23:17
  • With respect to the listener -correct
    – Old_Fossil
    Aug 2, 2023 at 2:24
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Late to this table but fans don't scream "I'm ON!". From the video, the fan(s) seems to ramp up, suggesting your cooling and ac system may use electronically controlled variable speed fan(s). Even my 20 yr old Saturn's dual fans don't scream at high speed. Mine has a three speed control, depending on coolant and ac demands to regulate speeds. I'll go out on a limb and suggest the dealer knows exactly what's wrong but padded the estimate or bill of replacing the condenser coil (and receiver/drier if its a separate part next to the c-coil) that's not contributing to the excessive fan noise (HINT). Both fans may need to be replaced so be prepared if that's the case. Dealers only see profits, especially when the problem may be labor intensive, hence padding an 'estimate' for unnecessary work. While your vehicle isn't old, cooling fans do wear out. Some lose a speed like mine, others may wear out from high use in hot areas of the country with a lot of ac use. If you manage to disconnect the suspected noisy fan that silences the screaming, that's one answer but the other one may switch to high speed if electronics detects the faulty (disconnected) fan. Some vehicles may switch on one fan for low speed, switch on both for medium, then switch both to high speed. As suggested, alldata.diy will provide service manual info, describe cooling fan operation and procedures for replacement. I've used alldata and Mitchell data. Both second to none against factory manuals. A subscription is very reasonable for diyers. Most repair shops use one of these for immediate online access then print info as needed.

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