Frigidaire stacked washer/dryer makes rattling sound for 5 hours after wash cycle completed

[RichardA]

Hello everyone,

Due to my lack of appliance knowledge, it's been tricky trying to research solutions on my own, since I am unable to identify the part that is giving me problems and therefore can't research that keyword.

Here is a link to the photo of the unit, and video of the problem: https://photos.app.goo.gl/oeQu8FitxvrBr6ao7

I am not sure what specific model this Frigidaire "Laundry Center" stacked washer/dryer is but what I know is that it's likely from 2005 when my condo was originally built. I moved in as the third owner in 2008. The two owners manuals I inherited don't even mention the model number. They just call the product a "Laundry Center". Even the brand name "Frigidaire" wasn't even printed on the front cover!

Anyway, there is a large hose (exhaust?) leading from the back of the unit up to the ceiling. On its way to the ceiling, there is a contraption. Occasionally, after running a wash cycle, this contraption makes a constant sound as if it's running. It reminds me of a car engine left to idle. When that does happen, the sound goes away after an hour or so. However, last night, it kept making that sound for 4-5 hours after the wash cycle was complete.

Thinking this contraption was running off electricity, I tried turning off the circuit breaker to cut power to the washer/dryer and hopefully kill the sound, but this action did nothing. The contraption continued to make that sound. Only about 30-60 minutes later did the contraption finally stop on its own, as if unprovoked.

Any idea what that contraption is called? Any idea what it does and why it was making that sound? Is it serious? I wish I knew what that thing was so that I can do research but I'm basically stuck.

Thank you!

[RichardA]

I can't seem to edit my first post, but I found the model number. Electrolux Home Products (not Frigidaire as the owner's manual indicates), model number MEX731CAS3.

[Budget Appliance Repair]

Since you are in a condo and the vent goes up to the roof, it sounds like the contraption you are describing is a "Vent Booster".

This would be an fan booster in the vent duct for long ducts to move air over the extended distance the vent duct needs to get up and out the roof.

Usually these units only operate when the dryer is operation with the use of a pressure switch sensing the vent duct pressure and which turns the booster fan on and then off when the dryer goes off, (there maybe some other mechanism activating this one so it runs for a certain length of time after the dryer is still off - but I've never heard of one that does that).

[RichardA]

Thank you, "vent booster" is pointing me in the right direction! A search on Google Images confirms this. Finally! Thank you!

The strange thing is, I seldom use the dryer. I can understand why this booster might run when the dryer is operating. But every time in the past when this booster ran past the cycle, it was always a WASH cycle, never a dry cycle. This week's episode was no exception... it was my weekly wash cycle and the booster inexplicably felt like running for 5 hours afterwards.

Surely, a washer does not use air which needs to be vented outside, correct?

[Budget Appliance Repair]

@RichardA I wonder if maybe they have a bunch of the condos all venting into a common large vent stack and they have it setup to turn on the vent boosters in all the units when any of the dryers are operating so that the vent from the other units don't back feed into the individual condo units.

I don't think this would be the correct way to do it and probably not up to code but all kinds of screwy things are done and found out there.

[RichardA]

That's an interesting theory. However, the sound being emitted by my booster only comes on when I use my washer, and only very occasionally. The law of averages says that with 12 condo units in my building, I would hear my booster coming on very frequently every time another resident does their washing/drying.

Instead, what I've noticed is that it only comes on after I use my washer, and very infrequently at that. When it does come on, it's about an hour. This latest episode was the strangest one because it lasted for 5 hours after the wash cycle.