Customer has a Rinnai tankless that is giving off error code 17. Upon inspection and after talking to Rinnai Tech service, determined problem was coming from combustion fan area, specifically the Venturi. I went up on roof to inspect the vent termination kit. The vent termination kit is missing it's top cover piece. When is rains water can enter the tankless unit from the combustion air and vent piping. As a result, the water is dripping directly onto the fan motor. The fan motor is completely rusted. After further inspection it has been determined that this fan is not repairable. Customer has already purchased a new tankless unit of the same model, but they we’re trying to see if a repair could be made to the existing tankless unit. We strongly recommend not replacing the tankless until the venting issues have been resolved. Recommended that they purchase a Navian tankless over Rinnai tankless. But, customer would rather use the Rinnai they already have. I showed Byr