Need an ingenious way to find something in the wall

[signal15]

Not really home automation persay, but I figured since many people here have probably dealt with having to track things down like this before, it's worth asking.

I *think* my bedroom has an HVAC booster fan hidden somewhere between the furnace and the bedroom. I used to be able to hear a fan at night when the furnace was on, and my room was always nice and toasty. Then one night I noticed I could no longer hear the fan, and it was cold. The air blowing from the vents was much less volume than before. Shortly after I noticed this, I started hearing the fan noise again, but this time with a lot of vibration. When the noisy fan sound was going, tons of air was coming out of the vents.

Now, it's been several months since I heard the fan noise, and my bedroom is a good 10 degrees colder than the rest of the house. Any idea how to track this down without tearing apart everything? The basement is unfinished, and it's not down there. So the only place it could be is at the top of the wall in the garage where the duct goes up to the bedroom, or above the ceiling in the garage (the bedroom is over the garage).

I cut a couple of small holes in the ceiling, but it's a huge mess because it's packed full of blown insulation. I tried an inspection camera, but I can't see anything because of all of the insulation.

The only two options that I can come up with are:
1. Continue cutting holes in the ceiling. It's not making noise anymore, so I can't pin it down that way.
2. Get one of those miniature remote controlled tanks with the UHF video camera that they used to sell on ThinkGeek.com and drive it down one of the vents in the room with a string attached to pull it out if it gets stuck. I can't find them anymore though, ThinkGeek stopped selling them.

Any other brilliant ideas? I called the company that did the HVAC in this house, and they said it must have been added later because they didn't put one in. Then they told me that they were still owed $18k on the system (builder went bankrupt), so I don't think I should talk to them anymore.

 

[Neurorad]

Long snake camera, used for plumbing. Rent it for a day?

 

[refinished]

Metal detector? The booster will have a stronger signal than a run of duct, but you may also find other things, like electrical wiring.

The booster will have a motor in it - magnets. A compass?

If there is a booster, it will be wired to the homes electrical panel in some way and there will be a lead from the thermostat or furnace control board to the booster relay unit. Since you only think you have a booster, I'd start by looking for the signs that a booster is in fact in the system before cutting any more holes. An electric damper can also be a fit for your description if the fan noise was simply the furnace blower sound makings its way down the ducting. I, for example, have a return grille site that does a particularly good job (bad!) of telegraphing the blower sound despite it's being one of the more remote.

Good luck.

Edit: the tank camera would not likely work inside a metal duct anyway!

 

[signal15]

There is no extra wire running from the thermostat or the furnace that looks like it would turn it on. But, I've seen them where they have a little paddle switch right before them, so when the airflow from the furnace turns on, it trips the switch and the booster fan turns on. It has to be one of these if it's there.

The duct is only metal until it gets into the wall below the bedroom. Then it switches over to one of those insulated flexible plastic pipes.

 

[Dave X10]

........ Then one night I noticed I could no longer hear the fan, and it was cold. The air blowing from the vents was much less volume than before. ......... When the noisy fan sound was going, tons of air was coming out of the vents.

I can't imagine a fan close to the outlet (as opposed to near the furnace) would be that effective. The fact that it worked well would cause me to believe it's nearer the furnace than the bedroom. If you actually start at the furnace... and touch/feel the duct-work as it leaves the furnace... you should find it. It might be in duct-work that leads in what may seem like the wrong direction.

 

[pipeman]

Long snake camera, used for plumbing. Rent it for a day?

:rockon:

Do this, almost guaranteed!

 

[judge_l]

Maybe try and find the 110 volt source for the fan. It is was added afterwards, the wiring was likey added to something... if something looks differant or not as neat as the rest, that might be a good place to start.

 

[apostolakisl]

I'm with the snake camera too.

But I have to wonder if there really is a fan. Is there any evidence that the house was remodeled? If the original guys didn't put it in (and they don't deserve their 18k if a booster fan is needed) and it isn't sitting in the open in the attic/basement, how did it get there?

 

[signal15]

........ Then one night I noticed I could no longer hear the fan, and it was cold. The air blowing from the vents was much less volume than before. ......... When the noisy fan sound was going, tons of air was coming out of the vents.

I can't imagine a fan close to the outlet (as opposed to near the furnace) would be that effective. The fact that it worked well would cause me to believe it's nearer the furnace than the bedroom. If you actually start at the furnace... and touch/feel the duct-work as it leaves the furnace... you should find it. It might be in duct-work that leads in what may seem like the wrong direction.

My old house had an addition put on it at some point. The furnace wasn't strong enough to actually push much air into the addition, so after I purchased the house I added a booster fan. I bought a centrifugal fan from a hydroponic supply house. The first time I turned that fan on, legos, action figures, and all sorts of other crap came flying out of the vents. I had to put the thing on a dimmer so I could turn the speed down, it was insane. So, effective fans do exist. Those little axial fans are junk, but the centrifugal ones are awesome.

The house I'm in now (with the "issue") has never been remodeled. It was built 4 years ago, but I was the first official occupant, and I moved in 1.5 years ago. The builder was building it for himself and was living here during construction. The bank found out, tried to make him start making payments, and he couldn't do it so they took the house away from him (along with 3 other homes that he couldn't sell). I am assuming that he figured out the bedroom was just way too cold in the winter, and he added a booster fan. The rest of the house is pretty straight runs from the furnace. But the bedroom ductwork has to go probably twice as far as anything else, and do all sorts of twists and turns.

If he added it at a later date, he did it before the garage was sheetrocked, or he went through the floor in the closet. I'm thinking about pulling up the corner of the carpet in the closet and seeing if there was a hole cut in the floor and then screwed back in before I start messing around in the garage anymore.

I don't know what else would cause my vents to blow at least twice as hard, and make noise like a fan, unless it was a fan. I could actually feel the wall vibrating in my bedroom, and putting my ear on it sounded exactly like the fan I had in my old place. And... If I went in between where I think the fan is, and the furnace, none of those walls vibrated. If the vibration was coming from the furnace, you'd think that the other walls would vibrate like that also.

 

[judge_l]

Can you try pushing something through the duct and see where it stops? A regular plumbing or electrical snake might work, but it might go right through the fan. Maybe something like a garden hose?

When my basement was finished, the HVAC guy insisted he needed to put in shut offs for each room. I told him they would be drywalled over, but he insisted and they are now covered over.

I have also seen TV ads for a duct cleaning company that uses an inspection camera to show you the inside of your ducts. Instead of renting a camera, just have duct cleaning done?

 

[BraveSirRobbin]

Weird idea, but how about a balloon or something that will float inside the duct, string attached, blow air or maybe run the furnace, see where the string stops, pull out and measure the string.

 

[pete_c]

An "old fashioned way" would be to take an old AM transistor radio putting it between radio stations and listen for the RF noise that the motor might be generating.

 

[DavidL]

Just put a new booster fan in near the furnace on the trunk to the affected room and forget about the old one?

 

[signal15]

Just put a new booster fan in near the furnace on the trunk to the affected room and forget about the old one?

The old one would be a restriction. Plus, there is no real good place to put it down in the furnace room. There is a LOT of stuff running through the ceiling up there.

Unfortunately, the AM radio idea won't work. The fan doesn't seem to be working anymore. That's a damn good idea though, wish I would have known about that a few months ago when it was still making noise.

 

[Madcodger]

I also vote for the plumbing / duct work camera. FWIW, if the ductwork was never cleaned after initial construction or a major remodel in the house (I think you said it was ~ 4 years old?), it might be worth it to just have a duct cleaning company with a camera come in an do it, and help you find the fan at the same time.

I was always skeptical that duct cleaning was needed, but for about two - three years after we bought our current house we found that it was dustier than we thought reasonable, and I was chewing through furnace filters (the 6 month variety) about every three months. We finally had one of those companies come in, after my HVAC guy said he thought it was a good idea (but doesn't do it himself). My wife was home that day, and said they removed a ton of old drywall dust and dirt out of the ducts. Turns out the previous owner had done extensive remodeling and must have left the system on the whole time. We've noticed a significant reduction in dust and I'm using furnace filters at a regular pace now (and they often still look fairly clean when I change them).

Whatever you do, please post and let us know what happens. This is a real mystery - good luck with it.