Forget it, I just used this wonderful thing called Google and answered it. I thought it might be a unique procedure for a specific car....but it's not. An r12-to-r134 conversion is an r12-to-r134 conversion. It's the same basic procedure on any car.

It seems to be cheap, but if done right is quite labor intensive. You're supposed to have to remove as much of the "mineral oil" from the r12 system as possible by removing the compressor, etc.
The other downer is that apparently once an r12, always an r12. Even "retrofitting" the system doesn't do 100% of everything, meaning your A/C will never be as efficient(cold) as it was on r12, or as an original r134 is. It will always be just a little less efficient.


Doesn't sound fun, but it's definitely doable. I think I'll just keep the '91-'93 cars in mind, as it might be too hard to find a '94 just to avoid this one issue.

 

Don't need the A/C up here as much as the San Joaquin Valley or the South, so I pulled the A/C compressor and got 3 - 4 mpg instantly! I'll take that for a dollar..

Then again, I endured eight years in Phoenix with 110 degF summers with no A/C... when your brain is fried into jerky, you don't notice things as much.

 

For r-12 systems you can buy freeze 12 at most parts stores without a card. This is a mixture of the two but works with the oil in your r-12 compressor. Oil is freon specific. You need the correct freon to match the correct oil and seals in the compressor to match that.

New replacement compressors come with seals competent for either oil or freon. Just use the oil that matches the freon you intend to use. Vacuum the system out before switching types.

 

Hot shot is a great replacement for R12 but you need a license to purchase it.:thumbsdow It is R414B and works nearly as good as R12. I also saw that freeze 12 was discontinued. If your local auto parts store has some, nows the time to get it.

 

An R12 to R134A conversion can be done on the cheap if you have the mechanical skill to do it yourself. Most full conversions will have you replace components and what not when really most of the time if you replace your fittings and run Ester oil, which is recommended for its ability to work in R12 and R134A systems, you will be fine. No it might not cool as well as OEM but it will still keep you from cooking. Or you could always leave you system as is, depending on whats caused your refrigerant to leak out throw some sealer in it and fill it with Duracool or Redtec.

 

I found these threads to be helpful:
http://honda-tech.com/showthread.php?t=2330778
http://honda-tech.com/showthread.php?t=2334672

This site has an interesting quote, but I don't know if the Tercel compressors have this part, because this site is for a 60's chyrsler. :lol:
http://teamchicago.com/imperial/imp-ac.htm Here's the quote:

For best performance, the only alteration to consider is to remove the EPR valve from the back of the compressor and install an adjustable thermal compressor clutch cut-off switch. That is because R-134 will easily take the evaporator temp down below freezing and the thermal switch can be adjusted to keep airflow around 34 degrees. The stock EPR valve is not completely happy with R-134 and might not provide cold enough air if you live in a very hot climate. That is the component that restricts flow, not the condensor.

That is very interesting to read, but I don't even know if a tercel would have that part on the back of its compressor, or if that is only for super old compressors from way back then.



The main issue isn't whether I have the mechanical skills to do it, it's that I don't know what the parts represent. Working on a car for me is putting parts names to an image and position/location in the car. A lot of these A/C parts that supposedly need to be replaced I don't know what they look like or where they are found, so I'm having a hard time comprehending the whole thing. I'm confident that once I figure that out I'd be able to do the actual labor part no problem-o.

 

Well, some parts to consider would be replacing the compressor and the o-ring seals at the unions. The shaft seal on the compressor wears out over time and is subject to leaking. Any leaks will result in a loss of oil. When installing a new compressor in an R12 system, mineral oil should be added to the low side port before re-fitting the unions to it. For R134a, the canister you purchase from the local auto parts store usually has polyol ester oil in it. Ester oil can be had separately but is extremely hygroscopic, hence they are stored in metal cans by most manufacturers. It looks like you need some pics judging by your post. I'll work up some photos from my paseo since i gots free time. In the meantime, check out this link to see how the refrigeration system in your car works. Its basic and if you need more info let us know.

http://budget-tires.com/ac.html

 

Thank you for that link.