This month’s troubleshooting situation involves a Rheem RRMA-A048JK10X gas pack. The customer called for service because, instead of warm air being delivered from the supply registers, all they are feeling is cold air.
When you remove the service panel and check the fault code light on the printed circuit board, you note a sequence of three flashes. When you confirm the code as “High limit switch protection device open,” you take the next step of checking the wiring diagram (Figure 1).