Air Conditioning Maintenance – Air Flow (Part 1)

Like they say, “Baby it’s Hot Outside.” Summer is here and it seems like each year it gets tougher and tougher to stay cool. Here are a few basic things to check to avoid major meltdowns on those summer cruises.

We discussed the cooling system earlier this year and that’s the number one concern: hot engines make hot interiors. If you’ve been following our Tech tip series, you’ve checked out the cooling system and prepped it for spring so you’re ready to move on to the A/C system.

To begin with, the A/C system needs a debris-free condenser in front of the radiator to allow ultimate interior cooling. Any debris blocking airflow will raise the interior temperature. Check the condenser fins for debris and if necessary use your garden hose to flush away the buildup. Stubborn debris may require air pressure to dislodge it, so we made an extended air pressure nozzle, allowing us to blow the debris out the opposite direction that the air flows through the condenser. I know what you’re thinking. If the condenser airflow is limited, engine temperatures would be elevated but air can flow around the condenser and keep the engine temp in range while causing poor A/C performance.

While we’re discussing air flow, we need to check the air intake part of the system. When normal A/C is selected, outside air is continually circulated through the cockpit with the air coming in from the cowl area below the windshield. 63-82 cars have minimal screening to prevent leaves and debris from getting into the intake air stream. The build up eventually limits airflow into the cockpit. The real concern is as the debris builds up it blows directly onto the evaporator and it doesn’t matter if you have the system on maximum or normal, A/C air flow can be severely restricted.

We have a simple to install cowl vent air filter (73-82) to keep the infiltration of harmful debris to a minimum. If you don’t have the filter and feel that the airflow isn’t what it used to be, especially if you have some tell-tale leaves lying in the passenger side cowl area, clean up may be required. To start with, the debris drops to the bottom of the cowl and builds up, eventually allowing the debris to be pulled into the blower motor. You can feel for debris when the A/C is on maximum by checking in the cowl vent door area at the passenger side kick panel. You may want to wear gloves as you never know what you may find in the bottom of the cowl area. Most likely you’ll find a handful of leaves that a shop vac will pull out quickly.

Here’s the rub though. If the debris is left in place long enough, it blows onto the evaporator severely limiting airflow into the cockpit. In the worst case the evaporator case has to come apart for cleaning. In most cases the blower motor can be removed and the shop vac hose snaked into the evaporator area. We use a piece of small diameter hose and connect it to the vac hose to allow the hose to get into the evaporator area.

We have a cockpit air filter (for 84-96) which does a great job of keeping dirt and dust out of the A/C ductwork and off of your upholstery. Leaves aren’t as big a concern on the later cars as long as the cowl screens are intact.

97-04 Corvettes can ingest leaves also and our cowl filter will keep fresh air flowing for maximum A/C performance and now the latest C6 Corvettes have a cabin filter to keep odor and debris from the cockpit.

If airflow is still a concern, the foam seals have most likely deteriorated and dried up affecting airflow volume. The leaky internal ductwork seals keep the cold air behind the dash. Improperly operating air distribution doors prevent air from flowing where you need it most. We have the necessary parts to reseal and completely restore your early Corvettes A/C inner ductwork and distribution system.

The parts costs are reasonable. The labor is extensive and requires skilled hands to make the system new again. We can take some of the trepidation away with our service and assembly manuals though.

Once you’ve got debris-free air flowing into the cockpit you may want to check the condensate drain at the bottom of the evaporator for plugging. Water should flow constantly when the A/C is on. When the drain stops up, the floor gets wet. The drain is close to firewall at the bottom of the plastic evaporator case on early cars (63-96). Later Vettes have the drain coming out the firewall below the battery area. Don’t use any sharp tools to dislodge any drain debris. Gently move a small screwdriver around until the debris falls out.

This article was written by Chris Petris for Corvette Central.