Responsibilities of manufacturer, retailer and credit card company.

zoob

Common sence is required, the service company and myself see this issue regulary and 90% off the time the appliance isnt at fault and thats why we're advising you to defrost the appliance first and see how things go.
Neither myself or the service company are trying to be awkward by advising you to do this first before sending an engineer 
Yes sounds like your unit if a full frost free model with a fan cooled fridge as well, but it still still need to freeze the air in the workings so the fan can blow the cold and frozen air into the fridge and freezer compartments
Its that unit that does a timed defrost every day and its most overly iced up and for the reasons ive given most lightly 

Grumpy_chap

Our "frost-free" fridge freezer had a similar issue (though it is older than the two-years of the OP's device) causing noisy running. 
We did enquire to the local service centre for repair and they said it was an easy repair as the temperature sensor that initiates the "frost-free" auto-defrost has a tendency to fail and that allows ice to accumulate on the condenser fan which then becomes unbalanced and makes noise.
Rather than pay for the repair, we just did a manual defrost and the problem seems to have gone away.  That was before Christmas so I assume we'll have to defrost again shortly.  We assessed that as easier than paying for the renewal of the temperature sensor.
The OP's fridge may have something similar.

aroominyork

Well, I'm glad I posted here before doing anything rash because the sound didn't appear yesterday. A self cure? My guess is the knowledgeable folk on here will say I unknowingly left a door ajar overnight and it took a week for the fan to clear the frost...?

PHK

It could have done. 20 years ago, I ran telephone support for a very expensive manufacturer of white goods. We would always send a technician out but 90% of the time it was a user related problem. (too much food restricting air flow, not keeping the appliance clean, door ajar light on, cordial in the ice dispense etc etc) 

aroominyork

So I phoned ao.com who set up a three way call with Hisense. Hisense's line is that it is probably ice in the rear fan compartment and a manual defrost should fix it. I'll do that.

I asked how they can market the appliance as frost-free. Their answer was that it is not frost - it is ice! They also maintain that it is best to manually defrost it at least 1-2 times a year. I followed up by email with a request for this to be escalated to answer:

- Is Hisense’s position that it is truthful to say this is a frost-free appliance, but that it is not an ice-free appliance?

- They advertise the appliance as never needing to be defrosted (“Total no frost: no frost, anywhere – ever! It provides a suitable condition which keeps food fresh and nutritious longer as no frost can be found in refrigerator, which means you don’t need to waste your cherish time to defrost.”). How is this consistent with the advice given by email and again by phone recommening a 24h defrost at least once or twice a year?

- If the ice builds up again after the appliance is past its two year warranty, what support will they provide apart from recommending a manual defrost?

I am sure they will wriggle their way out of any sensible or satisfactory answers. 

ao.com said they will continue to offer support after the two year warranty period. I wonder what that means in reality if ice builds up again every year or so?

Lomast

Any refrigeration system that uses a compressor has the potential for ice to form on the cooling system.
Frost free means inside the unit not on the cooling system that would be impossible.
Defrosting for 24hr every six to twelve months is good practice

RefluentBeans

I understand your frustration with Hisense, but you have no rights with Hisense. If you’re going to go down the ‘it’s not as described because of the never defrost ever’ claim; then that claim is with AO, assuming that claim is/was on their website when you purchased it. 

As others have said, you should still be doing regular maintenance on your fridge and that should do a defrost every so often.

Looking at AO’s website (and YouTube video that is currently linked on the website) they do say that the Total Frost Free means ‘you’ll never to manually defrost again’. From what you’ve said there is no build up in the food compartment and so unlikely that the main compartment needs defrosting, but the sound could be from coming from elsewhere (like the back of the unit). It’s this bit that appears to need to be defrosted. The frost free advertising claims on AO’s website is all about 

Again this is up to you how you proceed, but I do think this is going to be an uphill battle to get any ‘repair’ done/any refund. But if you do want to proceed with that, forget Hisense and stick with AO. Hisense has no obligation to you (other than potentially a warranty - which will be written very much in their favour). AO has obligations under CRA.

aroominyork

It was Hisense's website where I saw the frost-free claim. I did not recently look at ao.com's, but looking now it says "air is circulated across the freezer to reduce icy build-ups, making sure you never have to manually defrost again.". That's helpful to know!

RefluentBeans

aroominyork said:

It was Hisense's website where I saw the frost-free claim. I did not recently look at ao.com's, but looking now it says "air is circulated across the freezer to reduce icy build-ups, making sure you never have to manually defrost again.". That's helpful to know!

That’s what I would be arguing on the basis of. Unfortunately, you can’t argue to Hisense that the product didn’t match their description (as they didn’t directly sell you the product) and you can’t argue to AO on Hisense’s descriptions but you can argue based on what is on AO’s website. 

It depends what you want from AO. 

the_lunatic_is_in_my_head

RefluentBeans said:

you can’t argue to AO on Hisense’s descriptions 

You could in terms of satisfactory quality  

https://www.legislation.gov.uk/ukpga/2015/15/section/11

(2)The quality of goods is satisfactory if they meet the standard that a reasonable person would consider satisfactory, taking account of—

(a)any description of the goods,

(b)the price or other consideration for the goods (if relevant), and

(c)all the other relevant circumstances (see subsection (5)).

(5)The relevant circumstances mentioned in subsection (2)(c) include any public statement about the specific characteristics of the goods made by the trader, the producer or any representative of the trader or the producer.

(6)That includes, in particular, any public statement made in advertising or labelling.

(7)But a public statement is not a relevant circumstance for the purposes of subsection (2)(c) if the trader shows that—

(a)when the contract was made, the trader was not, and could not reasonably have been, aware of the statement,

(b)before the contract was made, the statement had been publicly withdrawn or, to the extent that it contained anything which was incorrect or misleading, it had been publicly corrected, or

(c)the consumer's decision to contract for the goods could not have been influenced by the statement.

It's fair to say information on a public website is something the trader would have reasonably been aware of.