A/C Conversion to 134-for 308

He is right. It won't blow as cold. Not even close to R12.

 

See what he will charge for adding dye (if really needed) than add nitrogen with a trace amount of refrigerant and look for/find the leaks that way. Fix the leaks, if any, change out any older parts like dryer and re-charge with R-12. I'd stay away from the 134 route if at all piossible. NOT necessarily in the above order.

 

I've converted my QV using this kit, and being SoCal, residence, this kit is not too bad, it blows pretty cold air.
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False economy. R134 works great in systems designed for it, but not nearly as well in R12 systems - essentially it's a capacity issue, R134 requires "more" and an R12 system doesn't have it. Repair the system properly and spend the money to fill it with R12, and you'll have as good an a/c system as a 308 can have. FWIW I drove my daughter to her 8th grade dance Friday evening with the windows up and the a/c on to keep her hair together. She complained it was too cold, although she was the only one arriving in a Ferrari.

It ain't great, but if a stock 308 system with R12 can keep the cabin reasonable driving across the southern US in July, then it's not too bad. Anyone complaining about it just doesn't have it working properly.

 

Your ac guy may decline to install it but Duracool has virtually the same cooling/system characteristics as R12; in fact it is a tad bit more efficient. THe problem is it is not legal in some states for installation in auto ac. So if you do a DIY, it's not a problem but ac service shops typically only work with 134 and R12.

Be sure you install a new drier and expansion valve with whatever you end up doing. It's almost impossible that the ones currently in the car are OK. Look up the cross ref numbers for those parts, they are on this site somewhere. I could give you the part numbers/internet stores for the 328 parts but they are different for the 308. Total cost for the drier and exp valve will be around 60-70 bucks.

 

I'll go to my deathbed wondering why anyone would consider R134 an "upgrade" for any R12 system.

I suppose I can understand if you live in a very mild climate and really don't use it much, but besides that, why make a bad system worse??

 

"why make a bad system worse??"

Because you can?

Don't do a 134 retrofit from R12 without changing the drier/exp valve, draining/refilling the compressor, and flushing the lines/evaporator/condensor. The oil in 134 is not compatible with the oil in R12. Plenty of oil will remain in the system after removing the R12/vacuuming and the new 134/oil will react to clog the exp valve. As noted, stick with R12 (or try Duracool).

The advertisements for "kits" that you can just evacuate R12 and install R134 with no other work is misleading. The change will function...for a while. But you will just be replacing exp valves regularly. Admittedly, it's' not hard on a 3x8 but try it on a MB! I learned the R12/134 incompatible oil lesson the hard way.

 

It isn't cheap but the cost varies. I have seen that and I have seen less.

 

You can't really say what the pressure should be. It changes with ambient air temp. A general guide is that with R12 static pressure should be roughly the same as ambient air temp in F. if the temp is 80F, static pressure should be around 80psi if the system is fully charged. But this is only a very rough guide. Operating pressures and vent temp vs temp of the air at the condenser tells you if the system is performing as well as it can.

If you can get 40F temp reduction between the condenser and evaporator, that's about as good as any ac unit can do. My 328 will do that but the problem is with the relatively low volume/distribution of the cool air from the evaporator. My wife's MB cannot cool the air as well as my 328 but it moves a much greater volume of air so it can cool the car much better.

 

That's insane. I had a friend who works at a shop get me two cans from an autoparts store for $30 a can. My home A/C guy sold me two cans for $15 a can. I've seen them on eBay for anywhere from $20 to $40 per can. $120??? No way. People hoarded it when it was announced that production would cease. Now no one uses it. So there's more supply than demand.

 

This might help:
http://webcache.googleusercontent.com/search?q=cache:HckBoC8hKHUJ:www.ackits.com/aacf/ptchart.cfm+r

pressures and temps.

 

R12 should be available on e bay for $40/lb. avoid rusty cans, though. Few shops though, will want to even deal with R12 anymore. but theyre out there. You can get certified for about $25 by the EPA.

If you go with r134a, better buy/retrofit a larger condenser. Single biggest factor in efficiency (besides the normal flushing/purging of old mineral oil). I woulod stay with R12. No need to mess with nitrogen- just put in new O rings (biggest source of failure /loss of refrigerant is O rings), evacuate at min of 29.9 Hg, NOT 29.8 or lower, for 1 hr, and watch the needle for 5-10 minutes at least. There is a HUGE difference in microns between 29.8 and 29.9. If leak, THEN mess with nitrogen if you like, and dye.

Yes, R12 is pricey, but after checking for leaks, youll be HAPPY. Oh, a fellow member above said "normal" to top off every 2 yrs- not realistic/accurate. A good system shouyold not loose gas for 5 yrs.

 

Fellow member suggested Duracool. Basically this is propane. Duracool is ONLY a brand, and other companies sell propane (eg: ES refrigerants). Much hype about it- I am using it currently in one of my cars. Not happy with the results. Only thing I like is its easy to install/charge, no need to evac, and no need to flush out original oil as propane is compatable with ALL oils in system. You may want to try it, then switch back to r12 if not happy. Propane residues will not harm a R12 or even an R134a system.

Trace of propane is compatable with all of the above. Thats the nice part.

Oh, yes, its flammable, but you already have a fire extinguisher in your 308, right??LOL

 

Propanes like Duracool ARE legal for car ac use in other parts of the world. Since they are "friendlier" to the environment than the Rs, I'd bet that within 5-6 years they will be legal/in use in the USA. The only reason they are not certified for use in car ac is because they have not been submitted for certification for that use. It is NOT in the interest of refrigerant makers to have propane type products certified...

You said you were not happy with Duracool's performance; could you be more specific? Since it is actually a tiny bit more efficient than R12, it should cool just as well if the system is in good shape.

 

I have converted many 308's and others to 134a and it works great. Ask carreaper - we just converted his new 328 and he called to tell me how cold it was in Savannah GA with near 100% humidity and 95 deg days. If your car has a piston compressor - get rid of it. buy a standard sanden 508 and swap the back plate so the factory ac lines and fill joints will bolt right on. Get a york to sanden conversion plate. The rotary is much more eff than the piston style york. That is the largest true improvement you can. The next car we do I will take photos and post a full write up.

Local Dr. wants his 78 308 GTB converted.

Joe Frazar
Savannah, GA

 

I just did the 134 conversion...evacuated system, did a leakdown check and put two pounds of 134 in along with a little dye (5 system treatments per dye can)...not as cold as my R-12 was but far colder than my system with zero R-12 in it!

 

I'd guess that the $120 can is a large commercial tank; 30 lb. is a common size. Many are now only partially full after years of sitting. The $20 cans are the typical 12 oz. size that were sold in auto parts stores. R12 recovery was big business in the 90's; "mining" it from old frigs, cars and window units. I knew HVAC engineers who poo-pooed the change to R134 but it seems to have work better than they thought.

 

You stated that you aren't happy with the results of using a propane based refrigerant and said you didnt need to evac the system.I would take all the gas out,pull a good vac on it and start again.Any moisture or non condensibles will only hurt your system.

 

We've been through this compressor change thing quite a few times. That York cooled US cars that you could fit a 3x8 inside of and the ac would run you out of the car. The compressor is not a problem at all. I agree the Sanden takes less power and is smoother to operate but the York actually has a higher capacity as far as moving refrigerant per the York and Sanden specs.

I am beginning to believe that one of the issues with the whole discussion is the lack of any standard definition of what constitutes "cool." I think we should be measuring cabin temp, not vent temp. One person might feel comfortable with the interior temp at 80 (like my wife) while others (like me) think it's too arm if the cabin temp is above 70 .

 

You're right. Cooling is combination of cold discharge air temperature and fan capacity. Its a function of pumping cold air into the cabin faster than it can be heated or leaked out. 50F at the discharge may feel cold, but it may take 40F air at X cu ft/minute to cool the cabin adequately. Solar heat load would be a factor too. I know from past projects involving HVAC design that industry specs define an acceptable inside temperature at a specified outside ambient; eg 70F inside with 95F outside, but I don't know what the appropriate value would be for cars in 1985. I have no idea how automotive designers deal with these things; some one in the industry may know.

 

Thanks, Mike, for reply. Yes, starting with abject lack of credible scientific data on results/performance statistics based on a large statistical pool of population. Most claims are word of mouth , anecdotal. I applaude the people that support propane. Also, I believe the scare about flammability is way overstated. There has been no serious accident yet to my knowledge of "explosions", etc, other than the famous "Porsche" incident that is shared on the internet, which involved a shoddy porsche ac system , including hoses/fitings that were cracked/rotted/etc.

11 million cars use propane. BUT, still, data is lacking. Why? Beats me, otherthan perhaps is it still a fringe population that supports it and EPA has not yet "legalized" it.

On my old 1988 ac system, which was aftermarket, I had R12 initially- cold as heck. R134a i it say, in 2005, stunk. Then tried the touted ES 12, in about 2008, and disappointed. Still, its about the same as R134a. I dont understand and am mystified how propane has higher thermal expansion values in theory than R12 but cant perform for Pippo!!!! Dang.

Now, maybe when my compressor quits and get new again, Im thinking of going back to R12.