Sorry Kurt, I can't help you. You will have to contact Bosch under warranty and ask them. My experience was that these codes were vague and could mean a number of things, therefore requiring their agent to attend the unit on site. I have since replaced my system with a Rinnai which is very reliable. It saddens me that Bosch are still selling this unreliable product which causes grief to unsuspecting buyers. Good luck.

Hi Lee

This sounds similar to the problem we had. The "b0" you are reading in the glass window sounds like an error code? My unit did not come with a manual that interprets these codes so we had no choice but to ring Bosch and ask them what it means. Bosh told us that the error code was not specific and could indicate a number of problems, so they had to send out their service agent. As you can see from my review this became a painful experience for myself, my strata manager and my plumber over a long period of time. Good luck!!