I went to a customer's business to replace a blower overload relay. I installed the blower overload relay and did some testing. While testing, I found that the heating was only working in the first stage. I diagnosed the issue as a faulty flame rod and flame sensor for stage 2. I will return next week to install the new flame rod and sensor. The customer's heating is working for now. When we install new parts, it will work at full capacity.