A few months ago I had to replace the A/C evaporator core and I was surprised that the lower 1/3 of the core was clogged with wet scum and dirt which I'm sure caused the leak. Like many new cars I decided to use an air intake filter. I would have liked to use a pleated filter but space dictated the use of a piece of filtering material as used on window A/C units. I cut and glued (weatherstrip adhesive) the material directly on the cowl screen which makes it easy to remove for cleaning or replacement. Hopefully it will allow my evap core live a longer life and it also filters all the air coming thru the cowl intake and into the interior.

http://elcaminocentral.com/albums/Mrapii-1979-El-Camino/IMGS0014.jpg

PS-The braided hose and wiring is for my LED illuminated NOS purge.

Isn't a lot of the black gunk mold?

The other thing you can do is minimize the dampness factor by shutting off the A/C a little while before you shut down the engine. This gives it a chance to thaw out and dry off.

Or at least that is my theory and I'm sticking to it :-)

Steve

your solution to the problem will not fix it. One, if you use the max mode on the AC, you will not be drawing air in from the outside, but only recirculating air from the inside which is the most efficient mode of operation. That accumulation is trash, over time, from the system due to a leak of water, leaves, etc. from the cowl area into the air box. This means the drains from the cowl area are leaking or plugged which allows junk to accumulate and also that the drains in the box also need to be cleaned as you discovered. Plugging up the grilles on the cowl will cause rain water to back up and rust out the lower windshield prematurely.

Engineer I think you need to have a better look at the HVAC system on the 5th Gen. First of all even in the recirculation mode some air is still drawn from outside thru the cowl vent and I believe this is done purposely to prevent people inside the vehicle from being asphxiated. Secondly all the air that goes thru the HVAC sytem is drawn thru the screen vent that I have put a filter on so even though water and maybe very very fine dust particles will go thru that filter leaves and other junk cannot enter the air box. Thirdly the cowl area where water would collect if the drains are plugged is made of plastic, no rust problems there. The AC evaporator core and heater core also have drains. I think I got it right and my only concern is that the filter would clog up so badly that no air could go thru but my close monitoring of the filter over the last few months doesn't make that likely.

Air in the car on recirc does not drawn in outside air. This is not for safety, never has, never will be. There is enough leakage around the firewall and such to allow CO to enter regardless of what the recirc position is.

Ahhhh....in the '60s the Federal Government mandated that all cars have a ventilation sytem that would insure fresh air into the interior of the vehicle and it was done precisely for safety reasons. In the recirculation mode some air is still drawn thru the cowl screen; just take a good look at the positioning of the door at at that setting.

Ahhhh....in the '60s the Federal Government mandated that all cars have a ventilation sytem that would insure fresh air into the interior of the vehicle and it was done precisely for safety reasons. In the recirculation mode some air is still drawn thru the cowl screen; just take a good look at the positioning of the door at at that setting.

Very true, and this straight out of my 5th gen (1983) Owner's Manual:

"Max (recirc) Air from the passenger compartment is mixed with a small amount of outside air, conditioned and discharged from the upper outlets..."

Mrapii, I suspect since you live in Hawaii you run your A/C a bit more than the rest of us. I bet your heater does not get much use.

I had to replace my heater core a couple of years ago. With the heater core out of the way I cleaned some black gunk out of the box, but it really was not that bad. I hit it all with a bleach solution which made me feel better, but probably did not do much for the future growth of mold. I don't park under trees and of course it is in my garage at night.

I have to admit I love the GM A/C system on my Camino. It will blow 38 degree air on a 105 degree day. After 15 minutes I have to turn it down or I get cold. My Porsche's A/C system will keep me kinda sorta almost cool on a 100 degree day, but cold is not even an option. I did not buy it for the A/C though. The Porsche is for hauling A** the Camino is for hauling stuff.

Yes the AC is almost always on. My air filtering mod is working quite well and I hope to get many years of use out of my new evap core. During the late '60s I worked at a Porsche dealership and did installations of a aftermarket AC unit. Boy those units were real mickey-mouse but still very popular here in Hawaii.

Mrapii, I had the blower motor out of my '78 a few weeks ago and found my AC evap probably 1/4 plugged full of crap, too. Lots of pine needles and fuzz. The drain holes were also full of doo doo so I'm sure that when I ran the AC the box was flooded with water. No wonder it didn't cool like I thought it would. I, too, thought about some sort of filter and thought about laying some fine window screen in to help filter out the big chunks and every few years pull the blower motor out and really give it a good cleaning. Upon looking at your setup and all the banter about airflow, how would a chunk of that 3M Filtrete stuff for home furnaces work? It doesn't have to be the 3M stuff but a pleated filter media, nonetheless. It'd be hard to cut a pattern out of pleated material and make it look good so maybe cut the filter out of the frame, stretch the media out and cut out a profile of the stock screen.
Granted, there is alot more dust coming into a car than your house but you can cut alot of patterns out of a furnace filter and just replace them when they get dirty.

I think that to be effective the filter has to filter out much of the finer dust which mixed with water creates the gunk-like mud. I'm sure that your idea will work well as long as the filter material will not readily absorb water and clog up. As far as maintenance I note that all of the newer cars with AC filter require periodic replacement. Let us know how it turns out.

When using the ac (5th gen) should always start in max setting until the interior reaches a comtfortable, then switch to normal thereafter. This helps keep the core from acummulating moisture wich causes mold and other problems. By the time you see steady smoke coming out of the dash registers its usually means its too late and the core is loaded with mung....