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Problem: Loose Insulation mats inside blower compartment are causing our AC to freeze up?

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Problem: We experienced low air flow in our vents so we changed our air filters, then looked at the unit in the attic to find that our evaporative coils were frozen and (what I think are insulation mats) located above and below the blower are being sucked in by the blower. We ran the fan alone with the ac off to defrost the coils but the insulation mats were still blocking the air flow. My question is what is the purpose of these mats and will our unit be okay without them? If they must be replaced, will we be able to purchase and replace it ourselves? Thanks for your time & may God bless all your endeavors!

Answer: Thanks so much for your blessings, interest in our website and the opportunity to do business with you! Thanks for asking a great question! Yes, I have seen what you describe happen several times before. The mats which are glued to the metal body of the furnace or air handler come lose and restrict the air flow going into the blower! The insulation mats are used to reduce noise and prevent heat or cold (winter time) transfer, build up inside your air handler. Without the mats you might get noisier blower air flow and you might get some heat entering the return from the hot metal duct work in your attic. The insulation keeps the heat out so that you do not get hot air pulled into the return. If it was me I would try to purchase some spray glue at home depot to re-attach the insulation pieces. Sheet metal shops use a special duct work insulation glue to glue the insulation in place. If the glue does not hold I would remove the inside insulation and insulate the duct work on the outside. Here in Louisville, KY it is HVAC code to have ducts insulated in unconditioned spaces like attics and crawl spaces. The insulation keeps the duct work from heat or cooling lose or gain. The supply lines are insulated to keep them from sweating water in the summer time. I hope you can easily get this fixed. I know that nothing is easy when working in the attic. Hope you can work up there in the early morning before it gets real hot! I hope that you have a blessed day and week!

Steve Arnold,

13 thoughts on “Problem: Loose Insulation mats inside blower compartment are causing our AC to freeze up?

  1. One of two Goodman mec96 furnaces were shutting down about 60 seconds after going into second stage which occurs about 8 minutes after the thermostat calls for heat. When you open the lower portion of the furnace where the blower and microprocessor PCB are located, the insulation to your left opposite the blower, return air is on the right in this furnace as installed, looked fine. It was appearing to be properly adhered to the side of the box.
    Pressing the interlock switch cleared the codes so I sat there for about 9 minutes watching what was going on. As soon as the blower started turning you could see the insulation sucking from the center toward the fan while all the edges of the insulation were well adhered to the side. But it was within about 4 in of the fan. In a commercial building I was troubleshooting HVAC problems for jll for whom I was employed for 13 years as chief engineer, a couple of large Joy fans were requiring bearings being replaced about every 5 years even with proper maintenance. They were positioned too close to a wall, they’re inlets. Soon as I saw them I knew what the problem was. Just like when I saw this insulation getting about three and a half 4 in closer to the inlet on the squirrel cage blower, I knew what the problem was. I held the insulation back with one hand while holding the interlock switch with the other and watched for 8 minutes until it hits second stage. I remove my hand from the insulation and it pulled out to about 2 in from the fan and within about 10 seconds the gas shut off. I didn’t wait to see the error code. Removing that insulation solve the problem. And while searching to seeing if others had the same problem, I found this post and will do what is recommended here, I will apply some insulation board to the outside of the furnace on that side. This is an unheated and of course uncooled raw space attic in central Maryland. This furnace was installed four and a half years ago in new construction. I am not impressed with the mec96.

    1. Thanks so much for telling us how you fixed the furnace problem! I really appreciate the time that you took in writing this so it will hopefully help others solve their furnace problems! Steve

  2. Steve, regarding: The mats which are glued to the metal body of the furnace or air handler come lose and restrict the air flow going into the blower!

    I have the same issue and the mats are degraded. Where can you purchase the mats, or the insulation pads that are glued to the inside? Is it a certain specific insulation required by code? Looking online and seeing what looks like the stuff (aluminum colored on one side) but it comes in much larger amounts than what I need.

    Do repare/service companies keep the stuff on hand and take care of that when you have them out?

    1. Hi Jim! Any sheet metal shop should be able to supply you with some internal duct insulation that you could use on the inside of your furnace blower cabinet. You, of course, will need to purchase some glue too. This is what I found when I googled the subject:…0.2..0.156.760.0j6……0….1..gws-wiz…….0i71j0i22i30.nP6uFrQBBEI I am sorry we do not stock this insulation. Thanks for asking this question. Steve

  3. Could you tell me how to refill gas in Window type AC which is fully sealed.

    1. Hi! On window air conditioners that did not have service valves, I used bullet piecing valves like the one sold on the following page: to add refrigerant. I hope you have a great day and a Happy New Year! Steve

  4. We have had the same thing happen. It took 21/2 years for the HVAC company to figure out our problem. My question is this — Is there any chance of fire or other “disaster if those are not there? I know when I tell the company I want them replaced properly I am going to get “push back from them and have to fight to get them reinstalled properly.

    1. No sir, there is no chance of fire or other disaster if the insulation mats are not there. There main purpose is for noise reduction and if the furnace is installed in an attic space or crawl space to keep cold air or heat from infiltrating the blower chamber. If your furnace is in an unheated crawl space or attic then I would have the insulation replaced. Thanks so much for your post. Steve

    2. 2 1/2 years to figure out that the mat had been sucked up onto the fins/coil? What the hell were they doing if they weren’t looking inside the unit? (Cause it should have been obvious – which also means they never cleaned the fins in almost 3 years). And you should not be getting “push back” from any company. They work to compete for your business. They work for YOU. Especially when your request is to have the unit repaired to the manufacturer’s specifications – you aren’t asking for some strange modification. Please get a new company. STAT! I agree with Steve’s advice, my advice is based upon their lack of customer service. I would leave it out if you aren’t familiar with the unit, and bring it up to a new company.

  5. We were experiencing low air flow cause of the insulation mats being sucked in by the blower. i did not know it at first though, our problem was in the heating i thought it was my board cause of an error 5 so i replaced my 20 year old one than a day or two later it starts kickin out a code 4 and doing some research & i checked the insulation above the fan cause my furnace also is in the attic laying on its side and i should have noticed it before, but i took the insulation out and now the fan blowing good and strong and should not kick the high limit switch,but i ordered a new one anyhow, along with running a new thermostat wire and stat,the old stat was a mercury filled ha.Insulation board on the outside is a good idea thanks.

    1. Hi Casey! Thank you so very much for sharing how you fixed your furnace’s poor air flow problem. Believe me I have had similar situations where I have replaced expensive parts when in the end found out it was a simple problem. I know that your post will help others in finding an inexpensive fix to their furnace or air conditioner problems. God bless you. Thanks so much! Steve

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