Has anyone had experience with converting a c3 system from r12 to r134.
The cost of r12 makes this look like an attractive alternative.

 

When I get my C3 back together, I'm going R134a. There's really no downside. Here's a link you will find most interesting...

http://www.id-usa.com/how_to.asp

 

Good info, many thanks

 

R12 and R134-A have significantly different molecular make-up. R134-A molecules are much smaller, hence the A/C system must be much tighter and secure in terms of fittings, hoses, etc. etc. I am no AC expert but I do work for a large air compressor manufacturer that makes air dryers for compressed air systems. When we switched over to R134-A we had to completely redesign our dryers included much improved fittings and hoses to accomodate the leak paths that are prevalent with R134-A systems. Check with someone who's an expert first---I believe you will have to change quite a few components other than just the "typcical system flush and refill with R134-A"...that in and of itself may run into some big bucks. If your C3 is a "only on sunny Sunday driver" like my '68 Big Block, put the R12 back in it--suck up the cost and enjoy your drive with the AC blasting! Let us know the outcome. My '68 has 255 AC....(2) windows down and drive it 55-MPH.

 

I live in Utah so mine is driven practically every day. I want to do it right so it's as much fun as it looks like.

 

Personally, I think it is way cheaper to stick with R12. It only takes 3.25 pounds of it, so less than $200 of R12 vs several times that to convert to 134 with new lined hoses, parallel flow condensor etc.

 

You may want to take a look at this site on R12 alternatives. I'm thinking of trying one of these when I'm done with repainting my '80.
Freeze 12 http://autorefrigerants.com/co00030.htm

The EnviroSafe looks like another option. 39.00
http://autorefrigerants.com/co00033.htm

I don't think that just recharging our old R12 systems with 134 will be efficient enough, but even an inefficient AC is better than none at all!!

 

I did my Ford 4X4 years ago and was able to get 58 degrees out of the dash vents on a 92 degree day in the shade of the shop. It is not a big deal.

 

Duracool is a drop in alternative. It takes about 50% as much as R-12 by weight. Therefore if you need 3 lbs of r-12 about 1.5 of duracool will work. It is equivalent to what is used in Europe for most refigeration.

 

I did my 72 Monte Carlo recently and cleaned all components. I can get 58 degrees as well now. You have to ensure the blower motor is good, evaporator fins are unobstructed and has no residual flush oily liquid. That said, my current stance is to do a Vintage Air R-134a system for my C-3

 

A lot of those parts are worn out on our cars from 30-40 years of wear, tear and rot.

 

58* does not seem very cool to me... I would check the pressures again. When my vette is blowing 58*(like before its cooled off all the way) I am suffocating...

 

58* won't cut it. I mentioned in an earlier thread that I recently did 2 a/c conversions: One from R-12 to Freeze-12 ('91 ZR-1) and a '80 from R-12 to R-134. On the latter only changed the dryer/accumulator and the compressor (it was fried). Both will cool to below 40* center duct temp. Did not use a parallel flow condenser on the '80 'Vette. It can be done. Don't chase your tail with over-looking trash clogging the evaporator fins and make sure the temp. controls work properly.

 

The R134a system on our 3500 express van blows a cool 39* at around 90* ambient. If 58* is all you can get, I'd check for proper operation or look into a performance booster additive.

 

Stating that you have 39° or 40° or 58° really doesn't say much.

Under what conditions are those temps.

ambient?
fan speed?
dash temp?
recirculate or fresh?
engine rpm?
length of time?

Fill that in and then give the center vent temp.
In reality that 58° may well be better than someone's 35°

 

VERY TRUE!! Lots of variables that can mess with vent temps. Here was my scenarios from today's cruise:

92* ambient
114* vent temp before turning on the AC, this was at cruise speed, windows down(yes its a hot B*TCH when the ac is off)

System ran in about 20 mins, fan speed on HI(C4 blower), MAX AC(permanent recirc), rolling about 65mph/2500 rpms, I get 49-50* vent temps in the center vent. If I pull the fan speed down to the 3rd speed(last one before HI) temps drop to 45*. At freeway speeds, 2500-3000rpms, it holds about 45*. If I slow down to 40-50mph or around 2000-2200 rpms, it will drop to 43-44* on the 3rd fan speed. If I pull the fan speed down to the 2nd speed or even the 1st speed, the temps drop to about 43*, occassionally touching 42* at 45mph cruise.

I found that I get the most overall cooling and best cabin temps(not vent) running the fan on the 3rd speed, it will blow steady 45* with decent volume. Running the fan on HI just overwelms the evaporator and really just doesn't cool as well. I can easily stay cool with the fan on the 2nd speed.

I have done this same test with ambient temps from 92-96* and humidity is always 70-80% minimum here in Houston.

I am using a digital stick thermometer that I have tested against an IR temp gun in a cup of 40* water and its dead on.

BTW I have two other regular stick thermometers and one shows I am getting 37-38* and the other shows 40-42* when at the same time, my digital is showing 44-45*.. The digital is the only one I really trust. I can tap on the other two and make the temps jump up and down.

This is on a fresh recharge of R12(about 2 months ago)

That detailed enough for you?

 

IMO...if you have a center duct temp. of under 40* at an ambient outside temp. of 90*, you will be cool. I'm not happy with my conversions if the can't achieve this temp. I close the windows, max. air (recirculate), fan blowing on condenser, 1,500 rpm engine speed. Temp. should be <40* in 2 or 3 minutes.

 

I had just finished a black BMW a/c and had it sitting in the hot Florida sun with ambient of around 95° for about 20 minutes with the windows up and on max, full fan. Temp at the center vent was 33°. The guys down the street that do a lot of limo a/c work saw that and couldn't believe it. They have never gotten a car that cold, especially black. I said nothing.

The secret is, when you have it on recirculate with the windows up, you are lowering the the heat load very quickly. It really isn't a good test. In reality, that car, under normal conditions with fresh air, on the highway, put out 55° which is still pretty good.

The way I was taught was to
Idle 1200-1500
Hood open (to allow max air thru condenser)
Windows down (to simulate setting on vent)
Set on Max (to shut off hot hood air)
Get pressures to normal readings after 15 minutes.
Fill slowly until evap intake (after expansion device) is the same temp as evap outlet.
Vent temp should be as low as it will ever be.

It's all relative. If 90 outside a 70 temp in the cabin will feel pretty good.

BTW, all new cars I know of, when shut off, auto matically turn the recirculate off and back to vent but that was for warranty reasons.

 

Especially if you're the one inside the cabin !

 

I converted my 80 over to R134a about 6 years ago...never looked back. Blows COLD air. I could never say that about the R-12.