Customer has a 11+ year old Rinnai tankless water heater that keeps tripping a 10 error code. Called Rinnai and they recomeded cleaning the exhaust fan, burner chamber, and all around cleaning the inside of the unit. After I went through the cleaning process the heater kept tripping the same error code, called Rinnai again. The tech had me use my manometer to check the gas coming from the manifold and he had me change the pressure on the gas valve inside the unit, tested and nw the unit seems to be working fine. The tech did mention the exhaust fan sounds weir and could be changed out, customer wants to test the unit for a bit and will contact us if we need to go that route. During this process I descaled the tankless on the other side of the home, and the customer will contact us next week to do the plumbing inspection as well as descale the unit in the garage.