PI 3B+ UART connections

I am having problems trying to communicate with my PI 3B+ through the GPIO14 (pin8) and GPIO15 (pin10). It worked perfectly before with my PI 2B.
Has something changed? I came across this article and I think it says it has but it confuses me!

Solved it. The problem was that the 3B UART connections I wanted to use were set to Bluetooth by default. Removing that enabled my python code to use GPIO14 and 15 as before. This article gives the settings needed to remove BT.