Does this make sense: AC Coil blocking air in plenum?


Old 01-19-04, 07:57 PM
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Does this make sense: AC Coil blocking air in plenum?

My furnace has been acting up. It takes forever to heat up and occasionally the furnace doesn't come on.

Had a service tech in tonight and he believes my A/C coil (which apprently is in the plenum) is blocking airflow up the plenum. The result is air is blocked so the furnace gets super hot and shuts off when a furnace indicator gets to 200 and some odd degrees.

Interestingly right above the furnace the plenum is super hot but further up and on the left side the metal is relatively cool. He suspects the block is on the left side hence why its cooler on that side.

The result is our furnace continuously turns off and on until the house reaches maximum temp.

We cranked up the thermostat and watched the furnace go off and on several times in 15 minutes despite the air temp being less than the thermostat.

The tech says I have to have someone come in and cut open the plenum to clean this coil and this could be expensive. My furnace is 14 years old.

Anybody have thoughts on what I should do?
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Old 01-19-04, 08:02 PM
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Sounds like he/she is right.. YOu'll need to get someone in to take it out and clean the coils.

Have you been using any filters in the past or the cheap ones?

Have the coil cleaned, and use the better pleted filters vs the cheap 60cents filter.

Once the coil is clean you should seen a savings on your gas bill, and your A/C for sure.

You could do it yourself but it's too risky to mess with for DIY.
Old 01-19-04, 08:42 PM
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Thanks jay11j,

I've been using filters that you clean on a regular basis but I've probably not cleaned them as religiously as I should have especially since I leave my fan running to circulate heat in the home.

I'm not well versed in this area (i'm into home theare and computers more than home repairs so if you need help on that just ask!) but what the tech was saying made sense and I was hoping for validation. I sense the repair will be relatively expensive since they have cut the metal to get inside and work on it.

My other concern was how long would it take and once they were in their would they try and sell me a new AC Coil!
Old 01-19-04, 09:02 PM
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I would not remove the coil! You would need to cut a hole in the duct but you can just use a non-toxic coil cleaner in a garden sprayer to clean the coil. If you cut in where you can see the underside of the A coil you can clean it just fine in place. You can place a new piece of sheet metal over the hole you cut and use....yep, duct tape!

I also don't have love for pleated filters because they work the blower motor too hard.
Old 01-20-04, 04:25 AM
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Chances are good that the coil is the culprit. Toss the washable and get pleated "$5.00 ones" not the fancy coated ones they are restrictive. and change them every 30-60 days depending on how the look up to a light.

Get a price on cleaning the coil and wiegh the differance on a new system that will run more efficiently because even though it may work good now 14 years is at the end of its life and a couple years from now it may just die on you.
Old 01-20-04, 06:27 AM
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Lightbulb AC

For now You should try and clean the coil or have it cleaned. This will save you a lot of $$$$ in fuel cost right now.
That wash clean filter that you have is what did it to you.when you wash them you do have to put a spray coat on them to get and hold the dirt.

I dont see why if you paid a tech to look at this he didnt clean the coil. when he said thats what wrong.??????????

Like Matt said 14 years , 15 years is about the life of a AC set up. Id get a new one .

Get 3 bids on the job for sure. Go for a furnace with a AFUE of 80 to 90 and a A/C with a SEER of 12 to 14. See if they wont clean the coil to get the job.

Go to to compare fuel costs

Old 01-20-04, 01:07 PM
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Thanks for all your answers.

I'm a bit embarassed to say this but I've been buying the filter you wash off every 30 days and frankly I don't think I've been always letting them dry thoroughly and I knew nothing of putting on a spray coat.

Is it more prudent to just buy the throwaway pleated air filters?
Old 01-20-04, 01:26 PM
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yes. as stated, use the pleated ones, just do not get too efficient of one, it will restrict airflow
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