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How to Maintain Window Air Conditioners

EastCoaster

Premium Member
Joined
Jul 29, 2020
Messages
11
Location
New York CIty
Model Number
SL24N30B
Brand
-major brand-
Age
1-5 years
We have a couple of large window air conditioners (24,000 BTU Friedrich SL24N30B; and 21,000 BTU Friedrich SM24N30A-A.) and a smaller window unit (6000 BTU Friedrich CP06G10B). We have a number of maintenance questions and I thought I'd put them all in a single post:

  1. Should the units be cleaned inside once a year in the Fall? Is this usually done on-site or have to take into the shop? (We will have the units professionally cleaned since they are too heavy for us to manage on our own).
  2. What are the most important steps to include in the annual cleaning? Should the fluid be replaced or checked for leakage?
  3. Our large units have permanent filters (I think they are called 'pre-filters'). They are in two parts that are hinged and fold out and separate for cleaning. Are they sufficient to use on their own or should we insert additional disposable filters (the kind that look like sponge rubber) inside them? And is polyurethane foam or fiberglass better for that additional filter?
  4. We put a pad on top of the unit to muffle the noise of water drops from a leaky roof gutter. But there is a vent on the top of the sleeve. Will the pad blocking the vent cause issues?
  5. One of our large units tends to cycle off for about 10 minutes every hour (ie, the compressor shuts off) even though the room is not cooled down to the level on the thermostat. The room is quite large at 20x20 feet with a 12 ft ceiling and large skylight, so it is really difficult to get the temperature down. Does the hourly cycle indicate the unit is too dirty inside, or starting to fail? Would a cleaning solve this problem? (it is seven years old and has never been cleaned).
  6. And a couple of related questions that we have long wondered about: Can mosquitoes and other bugs get through an a/c's vents and into the room? And what keeps pigeon droppings from falling through the top vent of an a/c's sleeve and contaminating the air?
Many thanks for this helpful forum.
 

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
4,215
Location
Ontario, Canada
EastCoaster said:
Should the units be cleaned inside once a year in the Fall?

I recommend they be professionally cleaned every 3-years, or every year if used in a high traffic area or dusty area. It could be done in the Fall or the early Spring before they're actually needed.


What are the most important steps to include in the annual cleaning? Should the fluid be replaced or checked for leakage?

Actual disassembly and the condenser thoroughly cleaned with a steel brush plus either steam or a chemical aluminum cleaner used. Even a slight coating on the condenser fins will retard cooling somewhat.

The refrigerant travels in a sealed system and should never leak out unless physical damage is done to the unit. The refrigerant never wears out.


Our large units have permanent filters. They are in two parts that are hinged and fold out and separate for cleaning. Are they sufficient to use on their own or should we insert additional disposable filters?

I'm afraid I have never dealt with anything like that. Check the owner's manual. Units with disposable filters are usually replaced during cleaning.


4. We put a pad on top of the unit to muffle the noise of water drops from a leaky roof gutter. But there is a vent on the top of the sleeve. Will the pad blocking the vent cause issues? ... 6. And what keeps pigeon droppings from falling through the top vent of an a/c's sleeve and contaminating the air?

Which exact model? I'll try to look it up to see how it is designed.


One of our large units tends to cycle off for about 10 minutes every hour (ie, the compressor shuts off) even though the room is not cooled down to the level on the thermostat... Does the hourly cycle indicate the unit is too dirty inside, or starting to fail? Would a cleaning solve this problem?

The compressor should usually run until the thermostat temperature setting is achieved. If it shuts off prematurely, it could be due to overheating. That could be caused by a dirty or plugged condenser, maybe a slight chance of failing compressor. It might also be caused by the compressor overload protector being weak and out of specification because of age or use. The only exception is if its control is electronic in which case it might be programmed to do that.

How long has it been since the unit in question had been professionally cleaned?


Can mosquitoes and other bugs get through an a/c's vents and into the room?

The only time outside air should enter the room is if the unit has a 'vent' feature and it is set to 'open', or they get around the edges of a unit not properly installed. Otherwise there should be little chance of that. If the vent needed to be open for some reason, a piece of window screen could possibly be fitted over the existing vent system to help prevent bug infiltration..


Dan O.
 
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EastCoaster

Premium Member
Joined
Jul 29, 2020
Messages
11
Location
New York CIty
Thanks so much for all of the useful information, Dan. Here are follow ups to your responses:

Which exact model? I'll try to look it up to see how it is designed.
Friedrich SM21N30-A (21,000 BTU). (This is in regard to the question about padding covering the top vent in the sleeve possibly causing issues).

The only exception is if its control is electronic in which case it might be programmed to do that.
Can you tell if the above model has electronic controls? (It does have an electronic remote but I am thinking your term might mean something else.)


How long has it been since the unit in question had been professionally cleaned?
Seven years. Could dirt have been built up that would cause the cycling on and off that I described?

Many thanks again.
 

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
4,215
Location
Ontario, Canada
EastCoaster said:
Friedrich SM21N30-A (21,000 BTU). (This is in regard to the question about padding covering the top vent in the sleeve possibly causing issues).

As near as I can tell, that is just another opening into the rear area of the cabinet. If totally blocked it could reduce cooling ability somewhat. If it is just a thick filter material you're covering it with and air can still pass through it, it may not cause any problems. Make sure all side vents remain totally unobstructed.


EastCoaster said:
Can you tell if the above model has electronic controls? (It does have an electronic remote

That is a sure sign of having an electronic control, yes. That control might be programmed to shut the compressor down periodically, but I doubt it. I do not know the actual programming of the control but I think such a built-in function would be pretty unlikely.


EastCoaster said:
Seven years. Could dirt have been built up that would cause the cycling on and off that I described?

Yes it could. If the condenser is dirty and/or plugged it will cause the compressor to work harder than normal which would usually increase the compressor's operating temperature. The compressor's overload protector is designed to shut the compressor down if it draws too much current or gets too hot, as a safety precaution... hopefully before any damage is done to the compressor itself


Dan O.
 
Last edited:

EastCoaster

Premium Member
Joined
Jul 29, 2020
Messages
11
Location
New York CIty
Dan - Thank you so much for all of this information. You have been a big help and I feel more informed now as I plan the maintenance for these units.
 

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
4,215
Location
Ontario, Canada
Dan O. said:
That is a sure sign of having an electronic control, yes. That control might be programmed to shut the compressor down periodically, but I doubt it.


I thought of something else, it could also be the relay on the electronic control that switches the compressor operation, failing. In such a case that would usually require the control circuit or relay board (whichever it uses) to be replaced.

Basically, when the compressor shut down someone would need to check to see if the compressor was still receiving power. If it WAS getting power but not running, it could just be the overload protector cutting out for whatever reason rather than a problem with the control system. If the control system was responsible for the compressor shutdown, it would stop all power from going to the compressor.

Dan O.

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