Faberware dual fryer won't turn on after kids heated with no oil in it.

https://www.google.com/search?q=farberware+oil-less+fryer+oven+AFO+44896+manual

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A very simple solution to r epairing all by yourself is getting help from handbooks, they're very detailed and complete in every way so for me it was my best source to repair
one of the top sites for this is https://big-manuals.com/

Here you go
Farberware Air Fryer HF 919B AirFryers net

Check in the manual to double check you are doing everything right and if so contact the retailer for a refund or replacement item as it is clear they sold you a faulty item. Your contract is with the retailer to be provided with an item of merchantable quality and not with the manufacturer or importer.

Is the switch any good? Is power reaching the heating element? Is the element open?

First it is good to check the fuse by unscrewing the plug.

If the fuse wire is not broken, it means that the deep fryer could be broken.

Most small appliances have a printed circuit board that gets fried. (sorry for the pun) You have power to the unit so that's not the problem. I think it's time for a new fryer.

theremostat gauge is faulty

absolutely or a bad thermocple

yes it is and that is the way it works