Thank you to those that participated in my A/C poll. I found some interesting things that were contrary to what I had always been told. I would really like to get a larger sample for more accurate results. A few of my findings with the data I was given. The “satisfaction index” is based on 1 being awful and 10 being terrific.
1. Initially, aftermarket a/c was favored. However there were only 2 responses with aftermarket; this is not a large enough sample to draw major conclusions. After some thought I removed these 2 entries. I will keep these and if I ever get more data on aftermarket satisfaction, I will re-include it. I also threw out 1 car that said his a/c wasn’t working. The rest is based on 33 responses.
2. The most favored was the 73-77 type. This goes against what I have always thought that the orifice tube style was better than the VIR style systems. Average satisfaction on the 68-72 system was just over 7, on the 73-77 it was over 8, on the 78-82 it was about 7.5.
3. I thought that engine cooling temperature vs: a/c type might help explain why the 78-82 cars had lower satisfaction numbers than the 73-77. The 78-82 results were that 63% of cars were 200 degrees or less, and 66% of 73-77s were 200 or less, however the max reported temperature on a 73-77 was 210 (1 instance), while the max on a 78-82 was 230 (4 instances 210 or more). From this I initially concluded that the hotter a car runs, the less satisfied with the a/c you would be, but then I noticed that the 5 owners that reported 210 or more all said that they were 8 or more satisfied. I wish I had more data on this, but this is what the numbers I have show.
4. R134 had more positive numbers than R12. This really surprises me. This may be skewed by the fact that I only got 1 response with a 73-77 that was using R12. Respondents were pretty evenly mixed R12 and R134 on both 68-72 and 78-82 systems. From this I presume that the VIR systems like R134 better than I have always been told. Average satisfaction on R12 systems was around 7.4, with R134 it was around 7.7.
5. One respondent with a 76 rated his system a 10, but said that R12 cooled better than the R134 he had in now. One respondent with a 79 said that R134 was blowing out air 8 degrees warmer than R12, he rated his system a 3, the lowest I used.
6. Not surprisingly, the ones with glass tops rated their systems lower than both convertibles and solid tops. Glass top average satisfaction averaged around 7, while both convertibles and solid tops were both closer to 8.
7. My conclusions for what they are worth. Either R12 or R134 work about the same. If I had an existing system I would keep R12, if I had a new system or was rebuilding one I would use R134 because it’s cheaper. If you have glass tops you are going to have a harder time keeping the car cool with the a/c. If you have a 68-72 and decide to add a/c, don’t avoid 73-77 parts.
8. My observations for what they are worth. Several people said they thought theirs would work better if they sealed their ducts. Several had C4 blower motors, but none rated their systems higher than 8. Most of the ones who rated their systems 9 or 10 had electric fans and/or new systems. My opinion is that this is where the most improvement can be found, regardless of car/year.
9. I welcome any additions to my data. If you have a C3 with working A/C-particularly a 73-77 using R12, secondly a 68-72 using R134, and thirdly convertibles-I would love to add to my data to make this study better.

 

Mark, thanks for taking the time to compile this information. My '74 isn't running yet, but it helps me in deciding which direction to take the A/C when I get to that point. Sounds like I can keep the VIR system and upgrade to R-134a and be happy. Oh yeah, and I need to seal the air ducts and install a water shut off valve!

Steve

 

interesting... ttt

 

Okay Mark, here is some info for you to add in.
I have a 73 big block coupe with R12 A/C, solid T-Tops
Temps run right at 200 sometime very slightly below.
A/C is very comfortable in side the car, no heat issues. If you are using an 0-10 scale I would put it at an 8. To me to rate a 10 the system would have to get ice cold and I have yet to see any Vette that will do that.

tom...

 

R12 is best. Several have got good results by just changing to R134 w/o major changes like condensor.
The large rear glass solar heater hurts cooling in 78-, that's why it's lower not to mention the additional interior volume, not really an issue.
Check seals on underhood A/C evaporator box.

68-77 coupe w/ solid t-tops (& R12) is best.
77- w/ factory A/C 9.5-10

The low inlet on R4 can be moved to the right away from headers & closer to the side.

A more efficient compressor can be used. Custom compressor, brackets & hoses (my own design). 10

 

R12 is best. Several have got good results by just changing to R134 w/o major changes like condensor.
The large rear glass solar heater hurts cooling in 78-, that's why it's lower not to mention the additional interior volume, not really an issue.
Check seals on underhood A/C evaporator box.

68-77 coupe w/ solid t-tops (& R12) is best.
77- w/ factory A/C 9.5-10

The low inlet on R4 can be moved to the right away from headers & closer to the side.

A more efficient compressor can be used. Custom compressor, brackets & hoses (my own design). 10

 

Nice job Mark. The more data, the better the decisions that we will make when working on these systems.

Thanks.

 

My 74 was just reciently rewired. In pulling the dash the rat's nest of wire,broken plastic instrument mounts, stuck linkages and unsealed ducting was found and fixed. I have heater block off valve, C4 blower and R134. On these 100 days, I give it an 8. To me a 10 would mean having to turn the fan off. I haven't driven mine long enough on a hot day s to see how cold it can get. I have a 30 min drive home in the heat. On a longer drive I might have to lower fan to med. Thanks for taking the time to sort this out for the rest of us.

Rick

 

Just to add to your notes. All 82's are designed to run at 195 + degrees. Below that and the computer stays in closed loop.

This might explain some of your findings with the 78/82 group.

And thanks for the time to put this together...

 

^ttt