I cannot find the filter and my furnace is not providing any heat. The limit switch is working fine as is the flame sensor. Diagnostic lights are: 1 slow bling 2 on Any clues? Thanks
Usually the filter is placed in the duct just ahead of the coils. Look for a “wingnut” that can be removed for access to the interior of the duct.
A furnace filter is to be placed in the return air side of the blower. Occasionally the filter is in a basket configuration in the blower compartment. If it's not in the blower compartment it should be pretty obvious and easy to see. If you don't have a filter your installer should be liable to replace your unit because dirt builds up on the fan blades, gets into the secondary heat exchanger and if installed, in the air conditioner's evaporator coil. Filters are an absolute requirement on a forced air system. The flash code is indicating high limit switch open. So she's too hot. Plugged filter will definitely do that. No filter means she's garbage, or at least needs to be torn apart and thoroughly cleaned.