What is the primary function of a normally closed (N/C) auxiliary switch

discoloration at the terminal pins (indicating high heat)

The board utilizes DIP switches located on the PCB

leak-free installation in standard gas trains

or oil flow

Lennox 99K70 Pump Cartridge Els PW 17895 What is the primary functionThe Lennox 99K70 Pump Cartridge is a critical OEM replacement part engineered for high performance fluid circulation in specific residential and commercial HVAC units. Designed to meet direct factory specifications, this cartridge ensures the hydraulic integrity of your circulator pump, preventing common mechanical failures that lead to system downtime. Whether you are performing a routine overhaul or responding to a total pump failure, the 99K70