Looks upside down.

 

It looks up side down to me. The arrow always points to the furnace. But let it live the rest of it's life being backwards as it already caught dirt on the wrong side and if you flip it over it will now suck that dirt in to the furnace.

 

Agreed.

 

imo. I don't really think it matters.

 

Looks upside down.
Throw that filter away, the 3M is likely restricting airflow through the unit.

 

this is the best advice...

in THAT location, the ONLY style filter you should be using is the fiberglass cheapo filters...

that location is the BARE MINIMUM for airflow, and using a high MERV rated filter can damage your compressor, and blower motor.

 

For the most part, yes. Those high dollar filters, that list all the scary stuff they catch, aren't much better then putting a piece of cardboard in the filter rack

 

Here is a much much better quality picture, none of that crude drawing nonsense. The filter compartment is the rectangular hatch that's slightly ajar just above the lowermost compartment (and just below the white drain pipe that leads outside), which I would imagine is where the blower motor and motherboard are located.

 

Don't want to damage that motor doesn't look like it can come out past those lines! Argh!

 

Sorry, what? I don't quite understand what you're saying.

 

Are you saying that it's damaging to the system to have the furnace filter hatch being slightly ajar like that?

If that's what you're saying, the problem is that the plastic knob and screw on the left side is damaged. The one on the right side is still working normally, but the one on the left side has a screw that's falling out, so it doesn't secure the filter hatch on the left side.

 

Your drawing is in error in that there are no motherboards, or anything else for that matter, in the metal box beneath the unit.
The filter is certainly upside down as air flow at that point is UP. It does not matter as it filters the same in both directions. However, do not flip the filter as that will put all the dirt it has collected on the outgoing side. I HATE, HATE, HATE (emphasis is clear, I hope) 3M Filtrete filters. They filter "better" by reducing the openings in the filter which has the effect of starving the system for air flow. That does reduce the efficiency and capacity of the system and it can reduce air flow to the point that the coil gets cold enough to form ice. I had two such service calls today because of 3M Filtrete filters. I wish I could wave a magic wand and make them all disappear.

 

A couple posts ago I posted a link to a much better image of the system, just a photo of the whole thing, no need for drawings. I can't edit it into the original post, or I would.

What filter would you recommend instead of the 3M Filtrete?

 

I did see the photo. The metal box below the unit is just there to provide a way for the air to enter the unit from the bottom. It is an empty box. Additionally, going back to the drawing, the duct labeled "duct going up" has air traveling down towards the unit. Also, what are the two holes about 2" in diameter in that duct?
I recommend an old fashion fiberglass furnace filter. The thing to consider is that the ONLY purpose of the filter is to keep the coil and blower clear of dirt. Furnace filters are NOT for making your house healthy as the marketing department would have you believe.

 

Ahh, my mistake, I thought you had only seen the drawing. I'm not quite sure what those two circular 2" holes are for. I once saw an HVAC tech stick a temperature probe through a similar hole on my own system at my home, perhaps they're there for the same reason.
Are these filters any good? They say Filtrete on them, but they look like basic fiberglass filters to me.
Or are these filters, that actually say Fiberglass on them, the definite best option?

Is my furnace filter cover being slightly ajar due to the left screw being damaged something that I should urgently seek to repair? I wish I could just get another screw.

 

3M Filtrete filters that I have seen are pleated paper filters that look like a filter for a coffee maker. I don't know why they would bother putting a brand name on an inexpensive filter.
As there is only a 20"x20" opening in those units, you need a filter that does not have the effect of reducing the space significantly.
As for the holes, I would at least put some tape over them.
The cover being slightly ajar is not an issue provided the room is not open to a garage or the outside.

 

Okay, I think you're saying that I should just forget the 3M Filtrete Basic filters and go to Home Depot and get the 4-pack of straight-up basic fiberglass ones.
Next time I'm over there, I'll take a close-up picture of the holes in the duct work to see what the deal is with them. I guess the concern is that they might be causing air leakage from the duct system?
The HVAC is installed in the laundry room, so it's not open to a garage or the outside.

 

Took some up-close images of the ajar filter hatch and the little black plugs in the duct system, and put them in the album.

 

I see the holes are plugged. That's good.
As for the filter cover, I suggest a small piece of tape. It's not a big deal.