Every part and tool from the field guide, with a fit check. Tools have exact part numbers; wear parts are matched by your appliance's model number or the old part. Check the fit before you buy. The field guide is coming soon.
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SUPPLIES + SAFETY
Pleated furnace filter (MERV your furnace manual allows)
Part no.size printed on your filter
✓ How to check fitBuy the size printed on your old filter's frame (length x width x thickness). If it is worn off, I measure the slot and buy the size that fits without bending. I never go above the highest MERV rating my furnace manual allows; a tighter filter can choke airflow and trip the limit.
✓ How to check fitNo part number to match. I use a fine non-woven pad, the maroon kind, never sandpaper or steel wool, and I only polish the rod until it is bright.
Kidde Carbon Monoxide Alarm, Plug-In with AA Backup Battery
Part no.COP
✓ How to check fitCOP is Kidde's complete model number for this alarm, as listed on kidde.com. No furnace fit check. Plug it into a wall outlet in the hallway outside each sleeping area and on every level, as Kidde's placement guide says, and not where it can be blocked or ignored. It is a plug-in CO alarm, not hardwired. I pick one with a battery backup so it still sounds in a power outage, and I follow the maker's placement instructions. Kidde says to replace CO alarms every 7 to 10 years; I go by the date on the alarm.
Resideo Honeywell Home FocusPRO N100 Non-Programmable Thermostat
Part no.TH1110U4000
✓ How to check fitHoneywell lists it as the replacement for the discontinued TH1110E1000/U. Single-stage 1 heat / 1 cool, 24 V AC systems only, battery or hardwired (C wire). If the old thermostat is marked 120/240 V or has thick wires joined with wire nuts, I stop. Power off at the service switch and breaker before I touch the wires, and a phone photo of every wire first. Only as a same-type swap for a battery-powered thermostat, with the same wires going back on the same letters. Anything wired differently, a C wire to add, or a heat pump: I stop at the wiring and call a pro.
✓ How to check fitRead the old sensor part number off the sensor body or wiring tag, or match the furnace's OEM parts list. This universal sensor has a 4 in rod that Robertshaw says can be cut and bent to match the original, and a 1/4 in quick-connect lead. I match it to the old one side by side: rod length, bend and mounting tab the same, so the tip sits in the flame.
✓ How to check fitRead the old igniter's OEM cross-reference or the furnace parts list before buying. This one is a silicon carbide igniter that runs on 120 V AC. I match the voltage and type printed on the old igniter or parts list: I do not put it in place of a silicon nitride, 80 V or 24 V igniter unless the maker cross-reference says so. I compare the mounting bracket, element shape and plug to the old one side by side. Sellers list it as the replacement for 271NM-style igniters (for example Goodman B1401009); it is a direct-fit part for specific furnaces, not a universal, so I match mine first.
Fit notes are guidance, not a guarantee. Confirm with your VIN, the old part or the maker's catalogue before you buy. Prices and stores change. Edition 4.0 · 2026-10-07
