GM 4108 OTR A/C air filter

[richard5933]

As I work to put things together after the repair, and I work to de-stink the bus, I thought about adding a thin layer of filter media with activated charcoal. Usually a good add in removing odors as air circulates.

The OTR system has an air intake right now consisting of a metal frame holding a few corrugated layers of metal screen between two outer layers of expanded aluminum.

I'm thinking of adding a 3/16" thick layer of activated charcoal embedded filter media on top of the OEM metal filter.

Anyone see any problems? My only concern was the possibility of restricting airflow, although I don't think that the layer is thick or dense enough to add much restriction. However, I don't know how close these things are to being choked already as they come from the factory.

[richard5933]

I looked through the manual to see if I could find any clues. Nothing about this specifically, but I did find something that I've overlooked in the past.

Apparently the manual calls for the metal screen air cleaner in the HVAC unit to be sprayed with an odor-free oil after cleaning. Presumably this is to help it attract and hold onto dust particles.

Not sure what to use for the oil spray here, but maybe the this activated charcoal layer would provide a dust trap while at the same time removing odors?

[jraynor]

I looked through the manual to see if I could find any clues. Nothing about this specifically, but I did find something that I've overlooked in the past.

Apparently the manual calls for the metal screen air cleaner in the HVAC unit to be sprayed with an odor-free oil after cleaning. Presumably this is to help it attract and hold onto dust particles.

Not sure what to use for the oil spray here, but maybe the this activated charcoal layer would provide a dust trap while at the same time removing odors?

On my 102A3, I took out the metal mesh since it was falling apart. Took off the side of the expanded metal that received the air then pulled all of the metal mesh out. Then I bought the blue washable filter and Lowe's and I stalled it after cutting to size. I did zip tie it in a few places to keep it from moving. I would say do that. Lots have done it before

[chessie4905]

You could use Pam.

[richard5933]

You could use Pam.

If was were to keep the metal screen filter, my thought was to go with a food-grade mineral oil. I've seen that used for the re-usable foam engine air cleaners.

Anyone know what Greyhound used for this when they were in service?

[buswarrior]

First I have heard of this oiling the passenger HVAC filter.

The old metal ones often were "cleaned" by burning them. The hair they ingested made it impossible to do otherwise.

Oiling it could easily lead to a "plugged" condition, unlike a dry filter.

Now, in busnut use, the conditions are different, fewer bodies depositing flakes and hair.

I would be concerned about whatever is used going rancid and making its own contribution to "more work"?

Happy coaching!
Buswarrior

[richard5933]

I read through the HVAC section in the manual many times, and it wasn't till this week that I noticed the one line about oiling the filter. Very easy to miss.

[sledhead]

this might work ?

https://www.actiontrucks.com/product-detail/KNN99-5000/filter-care-service-kit-aerosol?gclid=Cj0KCQjwp5_qBRDBARIsANxdcikAK4Ux4LDXwGHhA1OhVH0cFq11__JElqtEv9T4G_pGyD_r8pxbByYaAo0gEALw_wcB

dave