C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
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Old Jun 22, 2011 | 03:09 PM
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Default 1968 w/ac

I'm not sure even new, back in the day they cooled well for long.
There are a lot of things to consider, radiator 4-core for sure in a presurized system, a darn good fan to pull air across the condensor and a good clean evacuated sytem are all a must. After several yrs with many new parts and hoses I finally removed the POA valve and installed an orvice tube went R-12 to 134 and back again over the years it worked a little better but considering the car is a convertible it always struggled exspeacially in traffic. So I am looking to go with somthing after market utilizing as much of the original as most likely not possible. I even still have some R-12 around. Any encite would be of help. Thanks
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Old Jun 22, 2011 | 04:06 PM
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The C3 A/C system cooled well when new...and should do the same now, if it is in good working condition and charged up with refrigerant (R12 will cool better than R134a). But, you also need to check that collected leaves/debris are not blocking the airpath in the A/C plenum, and make sure the blower and vent doors are working properly. There are other "issues" that can cause engine compartment [hot] air to enter the A/C air path, and that will counteract much of the work that the A/C system is trying to do. Primary areas to check are that the rear hood seal truely seals with the rear fender surround. If not, hot engine air leaks out and goes directly into the "fresh air inlet" in the right side cowl area. Carpeting needs to have decent insulation under it in the passenger area (not required in the storage compartment area). And, the right kickpanel door seal needs to be in good condition.

You can buy a new aftermarket A/C system, but if those other "issues" are what's giving you the problems, they still won't be fixed when you get the new one installed. Fix the "issues" first; then see if the existing system still won't get the job done.
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Old Jun 22, 2011 | 04:56 PM
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I agree with 7T1Vette, get insulation under the carpet/firewall. Check the hood seal. I improved the cowl flapper so it seats better. Get a hot water shutoff valve. Get a C4 blower motor. Replace the drain tube under the evaporator. Keeping heat out is just as important as getting cool air in.

Do some searches, there are other tricks to keep heat out and improve airflow.

My system now does 48-52degF. I am working to get down to 42ish.
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Old Jun 22, 2011 | 05:55 PM
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All of the above, plus make sure the system is charged completely (the correct amount of refridgerant), did you evacuate the system when you chared it? A VERY small amount of air in the system will reduce your system's effeciency. Use gauges. make sure your pressures are correct, check your output temps, make sure it is set to MAX or recirculate.
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Old Jun 23, 2011 | 12:44 PM
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Thanks and all good advice. Maybe I am asking for to much, mine cools down in the low 40's, and I really like the C4 fan advice and will give it a shot. The rag top just doesn't offer much in the way of thermal protection.
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Old Jun 23, 2011 | 04:16 PM
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Originally Posted by dntoearthman
...The rag top just doesn't offer much in the way of thermal protection...
Once you cool the cabin air, you have to keep it in the car. What's the condition of your weatherstripping? Top. Doors. Door glass. Rear bow.

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