I am attempting to repair a laptop where the WiFi adapter works intermittently. This laptop has a physical switch to turn the WiFi adapter on/off. When the adapter is turned on, there is a solid orange light indicator. This light is a simple on/off indicator, it isn't meant to flicker like a hard drive indicator light. Since the issue started, whenever the WiFi adapter intermittently stops working, the orange light will start flickering or turn off completely. First thing I did was replace the WiFi adapter, but I still have the same issue. Is it likely an electrical component on the mainboard or could it be something simpler than that?
Update your router + adapter firmware first. Also check the condition of your antenna. It isn't beyond the realms of possibility that you have a second faulty adapter, though - especially if you bought used on eBay.
I usually replace laptop Wi-Fi cards with newer model if possible, like replace ABG with N. If you continue to have issues, they make tiny USB Wi-Fi adapters you can use instead. (8 USD)
I should also say it's worth checking for interference on that channel. Get a network analyzer (e.g. mobile phone app) and move to a better channel if necessary. USB adapter is a good call otherwise.