Our Nest heat link stopped working, and as this was fitted by the previous residents I didn’t attempt to contact Google for a replacement.
Thankfully it’s a common problem, and I diagnosed what was going on after watching this big clive video.
If you are after a replacement component, I got one from RS, details are as follows:
Diodes Inc 100V 3A, Schottky Diode, 3-Pin PowerDI 5 PDS3100-13 Stock no.:751-4654
I replaced the component using hot air, here are some pics of the repair process.