Our 73s A/C already had about $900 worth of repairs, and it still didnt work right when it arrived at Corvette Clinic. Several problems we found were the A/C had no volume of air at the vents; there was no low-pressure switch (to keep the system from freezing at road speeds); and the customer complained that it was still always hot. Prior repairs included replacing the accumulator, fan motor, and evaporator. Instead of looking at the entire picture, someone was simply throwing parts at the system, hoping that one would be the magic cure. It just doesnt work that way.
Another repair we found was the A/C recirculate vent door, which is on the passenger side, right in front of the windshield. These parts arent available anymore, so you may have a hard time finding them. Even so, youd have to look long and hard to find a GM parts number for duct tape and hardware cloth. If you want cold air, take the time to find the parts to do the job right. Also worth mentioning: Check the seal at the back of the underside of your hood. If this seal is damaged or if you have a cowl-induction hood without the proper seals around the air cleaner, it will allow hot air to enter through this vent and make your system a little less efficient.
Speaking of sealsthis is what was used for most of the seals on this system. Its designed to seal around the hoses as they go through the housings. This chunk was removed from the fresh-air vent.
Connections can be a major factor in how well your A/C unit performs. This high-blower connector was melted because of the heat generated by a bad connection.
Once again, another ingenious use for dum-dum.
This system was converted to 134a, as evidenced by the adapter.
But whenever you put in a different refrigerant you should also use the supplied sticker to inform others of the change.
When evacuating or charging an A/C system, identification of the refrigerant, proper tools, and knowledge are essential. NEVER evacuate a system by letting the refrigerant into the atmosphere, and be wary of the high pressure of the refrigerant and frostbite, which can result from exposure to the refrigerant.
With todays technology, hose clamps should never be used on an R134a systems hoses. The potential for leaking is greatly increased, and it could possibly turn into a safety hazard if the clamp ever fails. Dont do it.
When we removed the accumulator we saw a greenish residue at the seal. This is a material to help locate leaks within the A/C system. Even though the accumulator was new, someone was still trying to locate a leak. If you see any brown residue inside the hoses or anywhere in the system, stop and get the system checked, because the brown residue is either burned oil or the desiccant is bad.
We found the leak for them. When we were removing the hard lines at the firewall, we noticed that the small line that goes to the bottom of the evaporator was only finger tight.
Theres an O-ring inside the connection, so it probably did not empty the system immediately. This line is virtually impossible to tighten once the system is installed, which is probably why it didnt get checked.
GM used different compressors throughout the shark years. This is an A6 unit that was used until early 77 and then replaced with the R-4 unit, which was used through 82. The A6 unit is more durable, but it does have some problems. The low side hose is located right above the exhaust manifold, and the fact that its almost 30-year-old technology means well be replacing it with a Sanden unit that Chris offers in his kit.
There are some other problem areas inside the car, too. With the housings disassembled, check the diverter door for broken hinges. This will keep the door from closing properly. Think of it as running the A/C with the heater on.
We put a small piece of solid tube into the broken area and used epoxy to hold it in place. Check the operation of the valve once youre done.
Check all of the vacuum valve actuators to make sure they operate properly. A vacuum pump with a gauge will let you know if the diaphragm is cracked and leaking air.
Now is a perfect time to get the heater core checked for leaks and to make sure its not plugged.
The firewall of your Corvette separates you from the heat of the engine, so make sure the firewall is clean and straight where the A/C housing mounts to the firewall.
When reassembling the system, use urethane rope to seal the housing pieces together, and also to the firewall to keep that hot air from entering the A/C system.
We mentioned that one of the problems with our system was the lack of volume of air the fan was pushing out of the vents. We found several reasons for this and, though it may seem trivial, when you add up all of these problems, you find a drastic effect on the efficiency of the system. Broken parts like this one will let a lot of air escape under the dash instead of bringing it out to the driver and passenger.
Seals will deteriorate in time, and the fact that our system had been removed and reinstalled previously meant that the chances of the seals operating properly were slim. You can see how the seal is perforated where it mated, and if you tear the seal or it doesnt seat exactly the same way, each one of those low spots is a potential leak. Corvette Central has seals to replace any damaged ones, and now is the time to do it.
Another problem area would be the ductwork under the dash. Even though the ducting may be in good condition, GM used a double-sided tape to keep the parts sealed properly. Due to years of use or removal for one reason or another, the tape on our ducting has long since been ineffective. Once again, this doesnt make the air from your system cooler, it just directs it to you where it feels cooler and does the most good.
Check the diverter box to make sure the mating edges where the box screws together are sealed properly. This is a good place to use more of the urethane rope to seal up any leaks.