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Air-Cooled Comfort, Part II

Staying Cool In Your Shark

Andy Bolig May 1, 2001

Step By Step

Once we looked at the wiring harness for the A/C unit, it was obvious we needed to replace the entire harness.

Someone had gone “connector happy” all through the system, and that was a problem waiting to happen.

We also replaced the main harness and fuse box with an original style.

Someone had obviously pieced this system together with odds and ends. That simply won’t give the kind of performance we’re looking for.

Chris Petris helps the blower motor by running the high-blower power supply line to the battery side of the starter with a 30-amp fusible link instead of to the typical junction. This provides a better supply of power, and the 30-amp fuse link will not corrode like the original glass fuse’s contacts.

Make sure the A/C diverter door operates to the fully open and fully closed positions.

We showed how to repair the hinge on this door in Part I.

Use strip caulk to keep the air from bleeding out through any cracks when you reassemble the diverter box.

This will only increase the amount of air that comes out of the vents to cool you down.

This is a very important door. It keeps the hot air from the heater core and the cooler air from the evaporator separated. If you don’t make sure this door is sealed properly, you’re wasting your time—it would be like running your air conditioning with the heater on. Check the seal carefully.

Our vacuum lines were pretty bad, so we installed new ones from Corvette Central.

Take the time to tape the new lines together as shown. This keeps them from becoming a mess, and protects them from damage.

Chris takes the original hose connector and heats it up with a heat gun. This breaks down the adhesive that holds the hoses in place. He then takes a small screwdriver and works it around each one of the hoses to break them loose. Take your time so you don’t damage the connector. Chris then puts a dab of super glue on the new hoses and slides them into the appropriate holes. Mark what color hoses go where so you get them in the right place, or your system will not operate properly.

The firewall grommet for the hoses can be reused by cutting off all of the hoses on each end and then drilling out the rest of the remaining hose inside the grommet.

Be careful not to take too much material. You want the hoses to fit snugly without any restriction.

If you notice that the dual-action vacuum canister is not operating properly, check that the rear seal is in working order. If you need to replace this seal, you can find it in any GM auto built before 1979. You’ll have to drill the welds to remove the mount from the shaft and weld it back on once the new seal is installed. Pulling the seal over the shaft will cause leaks.

Corvette Central supplied us with a heater-box seal kit. This will ensure that you have good volume coming out of the vents, resulting in a cooler shark.

Chris uses Dayco-brand heater hoses, PN 80406 and 80417. They come in 4-foot lengths, and are already formed with a curve to go up into the heater box. He trims them to fit at the engine.

The name of the game is air management. The seal at the top of the radiator/condenser ensures that the air goes through the condenser to cool it properly.

The seals around the lines coming out of the evaporator box keep the heat of the engine from entering the system.

The directional ball vents have seals that keep the air pointed where it does the most good, and also keeps the ball vents from rattling even when you’re not using the A/C unit.

We used some weatherstrip adhesive to keep them in place.

Many times, the tabs that hold the vents in place are broken off.

Chris fixes them by grinding the surface flat and riveting a small, bent metal tab to make a new mounting tab. This will help keep the vent in place.

This is the entire duct system under the dash of a shark. Note that there are several connections throughout the entire system. Each one of these joints is a possible air leak.

Make sure ALL of the old seal is removed from the ducting before you install the new seal or it won’t stick.

Pull the backing from the new seal, stick it on, and trim it to fit. Once installed, the piece with the new seal should fit snugly into the rest of the ducting.

If you find any cracks in the ducting, seal them back up using a soldering gun with a cutting tip installed. Simply melt the plastic to cover over the crack.

Don’t forget to install a foam seal between the vent and the ducting. This will prevent a major leak and, because it is behind the dash, you’ll never feel the air.

The fresh-air door located in the lower kick panels should also be checked for a good seal. Corvette Central has replacement seals. All you have to do is drill the rivets that hold the two pieces together and install the new seal using new rivets to hold it in place. This will keep warm air from coming in the vents and warming the cockpit.

To get the most from your A/C system, you must keep the heat away from the fresh-air inlet. Make sure the seal at the back of the hood is in good condition.

If this seal is bad, the hot air from the engine can go right into the air inlet for your air-conditioning unit.

According to Chris, if the door weatherstripping isn’t in top order, it can affect how well the A/C unit cools.

We ran the clutch engagement power line through the cycling switch. This controls the refrigerant pressure and prevents freeze-up of the system.

This is the orifice tube supplied with the kit.

It fits into the line to regulate the flow of refrigerant in the system.

Compare this to the ’75 Valves In Receiver unit and you can see the amount of space that can be cleaned up under the hood of your shark.

Another often-overlooked part of the entire package is the clutch fan. This must work properly for your A/C unit to operate to its full potential. Check the fan’s clutch by running the engine to operating temperature, then shutting off the engine and immediately opening the hood to spin the fan by hand. If you do not feel the clutch engaged and providing resistance, the clutch is bad.

There are two different types of clutch fans: a coiled bi-metal spring and a wide, flat bi-metal spring. Each works effectively.

We were reconditioning the interior of our shark as we upgraded the A/C, so rebuilding the controls was necessary. Corvette Central offers the faceplate and control wheels as a kit.

While we had the controls apart we took the time to clean up the contacts for the switches. Just one or two passes of a fine file or sandpaper is all that’s needed.

If you need new contacts, Corvette Central has them. Make sure you set everything up so the switches operate at the appropriate settings on the faceplate.

The control wheels operate cables that curl up around the ductwork. Take your time to situate the cables so they operate without binding. Make sure you get all of the travel necessary.

Make sure all of the connections have the O-rings installed or you’ll have a leak.

Chris’ kits come with the fittings crimped to the hoses for a clean, easy fit.

As mentioned in the first installment, you should NOT use hose clamps for any of the hoses.

You can use either R12 or R134a in the system. Use the correct connections supplied in the kit, depending on what refrigerant you’ll be using. A trained technician should check and fill the system so it can be properly evacuated and checked for leaks. Also, the technician should put in the correct amount of oil and refrigerant, or the system will not operate properly. Excessive refrigerant can hinder the cooling capacity of the system.

With the system fully charged, we could sit back and enjoy the cool breezes. By taking the time to seal up the system properly we were able to direct enough air through the vents to keep a section of yarn suspended indefinitely with cool, refreshing air—just in time for the summer season.

In the last installment we looked at a few problem areas that haunt many of the shark-era Corvettes. Now we'll look at some improvements that will optimize a shark's A/C system. Depending on the condition of your system (and how cool you want it to be), some of these steps may not be necessary, but they are definitely worth considering.


Corvette Central
Sawyer, MI 49125
Corvette Clinic
Sanford, FL

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