Baxi E28 fault

DISCLAIMER: This video is only intended for use by qualified Gas Safe Registered engineers. You must not attempt any work on your boiler if you are not qualified. You must always carry out 26.9 checks upon completion of works on a boiler. ~ So this was an interesting one that I came across the other day. It was one I've not had before and it threw me. The boiler was showing E28, which if you check on Baxi Toolbelt says Flue Thermistor fault, so I'd swapped that round already but it was still giving me the same fault and it wasn't resetting. Had to call up Baxi Tech as I wasn't getting anywhere and they told me to check the last 2 blue leads on the X401 connector on the PCB and I should be getting around 20kΩ which I wasn't. He then got me to check the continuity on the air pressure switch, which should be making when at rest, but it wasn't. I then noticed the condense connected to it and thought let me check that. Disconnected it and it just all came pouring out! Cleaned out the trap, put it all back together and voila it works! So at the end of the day it ended up being a backed up condense issue. The resident only told me at the end she's having trouble with her sink draining away and this now all made sense! The reason the boiler throws up an E28 fault code is because if you trace the wires from the flue thermistor, they're connected in series to the APS and then back to the PCB, hence why it will keep throwing up a flue thermistor fault, when in fact it's the APS...