A long long time ago…when I was new to this business, a furnace had a gas valve, pilot, thermocouple, fan limit control and blower motor. I carried all of these on my truck and rarely did I have to leave the job to get parts. As advancements have been made in furnace efficiencies, these generic parts were replaced with OEM parts, (furnace controls, inducer assemblies, gas valves, etc). Manufactures such as Honeywell, ICM, White Rodgers and many others began making aftermarket replacements for these OEM parts as less expensive alternates to the OEM. What to do?
The OEM part is always the best choice. For starters, many furnaces have 5 and 10-year parts warranties. In these cases, the OEM part must be used to receive warranty credit. Also using non-OEM parts may void warranties and reduce the operational efficiencies of the equipment, while in some cases altering the equipment operation. Aftermarket parts will normally require some retrofitting or rewiring while the OEM part will be an exact replacement. The OEM part may be more expensive but it is the correct part for the job. It will be faster to install and it will ensure proper equipment operation as designed.
If you do decide to go with aftermarket parts, or the OEM part is no longer available, don’t just get the model number off the equipment but also the part number off the old part. Getting part numbers and descriptions from the old part as well as the equipment model number will greatly aid in finding a functional replacement.
For a blower motor, what is the HP, frame size, rotation, enclosure type, voltage and mounting characteristics? Select a motor that is of the same type, voltage, and similar HP. Never go down in HP and going up too much may cause problems as well. As many OEMs use flex mount (welded legs), belly band flex mounts in 3 and 4 leg configurations are available. These mounts will allow you to reuse the original mounting holes. There are also universal motor mounts for retrofitting.
With gas valves and ignition controls you need to be very careful, and never guess! Is the opening speed the same, (slow, fast or step opening). Does it have the same number of stages and gas pressure range? Do we need a pilot port or is it for direct ignition, spark or hot surface? Universal valves are available that will work for either. Is it standing pilot with thermocouple or power pile? What is the voltage? Does it have any special features or characteristics? On many 90% furnaces, the vent on the pressure regulator is connected to the burner box with a rubber hose. Many aftermarket valves have a tapped vent fitting on the regulator to provide for this connection. Having the part number off the valve aids greatly in selecting a replacement as well.
Most ignition controls will easily cross aftermarket controls. Make sure the ignition type, ignition timing, and lockout type are the same. ICM, Honeywell, and White Rodgers are now making aftermarket integrated furnace control modules as well as ignition modules for aftermarket replacement. These may require the use of jumpers or wiring harnesses to fit your application. Never guess when dealing with ignition controls or integrated furnace controls! With the part number from the old control, use only the replacement found on published cross-references from the manufacturer.
Many others aftermarket parts are available such as exact replacement inducer assemblies, universal hot surface igniters, fan limit controls, fan timer boards and many others. Your supply house (that should be B-Y), can help you with the cross-reference. Honeywell, ICM, White Rodgers, Robert Shaw and other websites can also help you with your part selection. In the end, however, it is up to the Service Engineer to make sure the aftermarket part you are using is the correct replacement for the application. Never apply a WAG when selecting non-OEM service parts!