Hi thanks, looked at both on the fan side and the duct side. Held a flashight in the a coil and could see the light from the other side. Didn't have much access to check every square inch though. Model number of furnace: Carrier Weathermaker 58SXC060 Series 100 installed in 1992. FYI put a temp probe in my vents in my office at home 66 degrees in the cold air return and 82 coming out the heat vent, but no velocity not getting the house over 67 degrees. Believe it was in the teens here last night.