battaninic

I recently purchased this device off eBay knowing that it was unable to receive a charge. In the seller's pictures the device...

I recently replaced the keyboard, battery and trackpad on a macbook pro 15" mid-2009 unibody. The keyboard and battery work f...

Most likely it is to cool your CPU or other components of your laptop. Do you know if the heat is coming near the battery, or more towards the screen? If most of the heat is on the battery, it may be time to replace said battery with a new one. If you are able to, I recommend cleaning your fans (you will most likely need a screwdriver to do this and this would probably void any warranty you have). The other option is to by a laptop fan cooler with fans, I used to use one on my older laptop, and it did help keep the machine cool.

Does the phones logic board show any signs of corrosion? If so, try brushing it with a 90+ isopropyl alcohol

Sounds like you received a faulty battery, I would contact your supplier and explain the issue to them. They should be able to send you a replacement or give you a refund.

Have you tried restoring to iOS 9.3 through iTunes? I have no idea why this error would be affecting you as this is supposed to only be an issue for iPhones with touch ID sensors, which the 4S does not. Are you getting error 53 or something else? This is the apple response to error 53 I found: https://support.apple.com/en-us/HT205628