Our Rheem RHSLHM3017JA air handler is making a "burnt wire or hot plastic" smell again. The first time it was on heating and we smelled it just before the transformer blew. It blew the transformer on the primary side of the wiring - not the low voltage. We've replaced the control board, replaced all the thermostat wiring from condenser to air handler and air handler to tstat with 7strand/18ga tstat wire, replaced the thermostat itself and replaced several 5amp fuse "kits" that we always put on the low side (now have the 5amp fuse kit on the hi side too)to protect the transformer. Now it is on cooling mode and we are getting the same burnt wire/hot plastic smell again! Please help? ~marilee