hi, I have BOSCH Tankless T9800SE 160K BTU showing C1 & C2 errors. Intake pipe distand is 39 foot & Outlet pipe distance is 43 foot, I am having this Machine from last 5 years working fine, but from last couple on months showing this errors. So I did many thing, but none fix the problem, as follow below.
1--I did Camera inspection in Intake & Outlet pipes all clear (not any debris shows).
2--I did Air Filter Clean & Water Filter clean, all clear now.
3--I did DESCALING of Machine.
4--I did Auto Tuning of this Machine to adjust Air & Gas pressure automatically.
After many different things still showing C1 & C2 errors, some time in a week and some time in couple of days.
The Butner mesh is plugged with dirt.
Take apart the burner, replace it (clean it) and put everything back.
Parts you should order
8738725270 Outdoor air filter
8738715160 199k Burner surface(includes burner gasket)
8738720126 Gasket Set
Check out this video
https://www.youtube.com/watch?v=r4SztAqCYSw&t=57s
And when I unplug & replug Machine, at that time at the beginning it will show SOLAR on display (Solar blinking on display), so what its mean of SOLAR showing on display, as you can see in photos.
Oh crap. Dude. Are you a home owner?
The solution to this issue involves taking stuff apart and putting it back together. Bad reapplication of gaskets can cost you the entire unit.
Consider maybe having a tech do this?