Thanks for the advice. Was at CW yesterday and bought a screen for the Furnace. Found some screen at Lowes for house vents. For what it is it is over priced. I will use to for the Frig, A/C and hopefully the water heater. I have the older Coleman A/C that has large opening screen probably just to keep leaves out and will replace it with the new smaller screen. I will have to make it large to keep the air flow up through the condenser coil. Yes the smaller screen should have been something the factory should have done, but damage the parts means sales of replacement parts.
Thanks
Buster