Missing AC Evap.Drain Tube Fix

[George Black]

68-82 corvettes have an AC condensation drain hole on the bottom of the evaporator housing box. The hole had a plastic/rubber cap with small opening to allow drainage, but to keep bugs,dirt,debris out. It also kept engine heat from entering into the AC/Evap. assembly; prevented cold AC air being lost when AC was on. It was Group 9.211; GM Part # 3021960; now discontinued. It is not shown in the AIM. It is shown in the GM corvette parts catalog in an exploded diagram in Group 9.

Fix: Go to Lowes. Purchase 1" PVC cap (for about 50 cents!) Drill 5 small holes in cap to allow for drainage. Attach cap to drain hole using adhesive. (spray paint cap black if you want it to look OEM). or, go to www.oldairproducts.com and purchase rubber drain tube/clamp, part # 21-5004, for $8.50.

For photo of GM Part # 3021960, go to Ebay auction no.2478331706 and look at the bottom of the evap. housing unit. It is the small black cap.

If you do not have this cap, turn AC on MAX, get under your car, and feel the amount of cold air coming out of the evap. drain hole! When AC is off, the opening will allow hot engine heat to enter the system, which ends up in your AC ducts/vents--not to mention dirt, bugs, road debris. etc.

Just a tip I thought I would pass along with the hot summer upon us!

 

[photovette]

Great! I wondered why that hole was so big!

 

[Bob Chadwick]

Great tip. I hope you don't mine but I have added it to a web page I have put together trying to deal with hot air issues on my Corvette.

Here is another trick that I learned courtesy of Vettfixr at Corvette Forums.

At the bottom fo the plenum where the air enters the system is the drain for any water that enters the system from the hood area. It is a large hole that allows hot air to enter the system from the bottom of the car, particularly if you have added headers. Put a shop light in the plenum from inside the car by taking out the recirculation door. Go under the area and you will find the drain easily enough. Place a drinking straw in the low point of the area and seal the hole up. Once the caulking is dry, pull the straw out and you now have a small hole that should drain this area adequately and at the same time reduce the amount of hot air that can enter the system.

 

[photovette]

One of the best things I did to my a/c is to seal around the evaporator coil on the INSIDE. This way all the air is forced through the coil instead of sneaking around it. My duct outlet temperature dropped 10F with only a small decrease in air flow. I used No-Drip-Tape (Lowes), and fished it in through the resistor bank hole.