Open Circuit Thermocouple Test with Terminal Block
On natural vent appliances incorporating a vent safety switch (VSS) as part of the thermocouple circuit, you can use the ECO (energy cut off) or terminal block on the thermocouple as a test point for gathering information. By removing the VSS wire on the pilot assembly side of the terminal block and then touching your meter probe to this point, and with your other on the thermocouple casing, you can obtain the open circuit reading.
While space may be limited on an insert, this point can be accessed on RHE (Majestic) style inserts by removing the logs and looking down through the combustion air ports in the burner tray behind the burner. On the new LHE (Majestic) inserts, there is a removable access plate on the right side of the burner that allows you to easily access this point. The VSS is mounted on the rear of the insert under the draft hood. To access the VSS on an RHE (Majestic) insert, the insert must be removed from the firebox.
On the LHE (Majestic) inserts, the VSS can be accessed the same way, or through the firebox by removing first the top baffle, and then the access plate at the top right side of the rear panel. The switch is attached to a bracket that is now accessible through this opening.