I am not real happy with my R134 conversion. The 50° duct temps don't really cool the car when it's 90° outside.
My pressures get too high before i added all the R134 as well, 30psi/300psi with several ounces of R134 left to add.

I have researched and found that R134 systems are designed for parallel flow condensers, not serpentine flow condensers like we have in 3rd gens.

Parallel flow condensers are supposed to perform much better and should allow me to run a full charge of R134. has anyone swapped their condenser for a parallel flow condenser? if so where's the best place on-line to get one for the money?

 

Sounds like you're fully charged, and possibly overcharged. How much have you put in? Your charge level of 134 is much better determined by your gauges than by weight. I'm assuming you referenced the retrofit article in the tech articles? It's a good article, except that it tells people to overcharge. It states that the original charge for thirdgens was 3.00 pounds. My car's decal says it's original charge was 2.25 pounds. Before cfc's were known to cause a problem, cars were often overcharged, even by the OEM specs. R12 was cheap, not known to be environmentally hazardous, and very tolerant to overcharging. OEM's could take a system, find out what charge was sufficient (2.25# for our cars), and just toss in an extra 3/4# as a small leakage reserve. When R12 was discovered to be a problem, and it's price started going up, that extra 3/4 didn't get put in anymore. That's why older cars being retrofit often take as little as 75% of the original R12 charge.

If you got 2 pounds in there, you've got plenty. When I do retrofits, I don't even look at the original R12 amount anymore. I let my gauges tell me when enough is enough. My conclusion is this...why try to calculate it if you have the tools to measure it directly?

Did you flush with your retrofit? It's not necessary to do so, but if your object is not just to cool, but to get cold as possible, the old oil really needs to come out, and when you charge with new oil, use only 6 ounces (that's all an R4 compressor needs).

Parallel flow condensers are supposed to be better. I've been looking for a place to get a replacement one for the eventual retrofit I know I will need, but haven't found one yet. I have found this: http://www.ackits.com/index.cfm?fuseaction=Parallel
The have a variety of different condensers, but you will have to fabricate your own lines and mounting brackets. BTW, our cars don't have serpentine condensers. They have tube and fin condensers, which are even worse!!

Have you checked that your current condenser is good and clean? Are your fans in good shape, and both running when the ac is on?

If you would like to simulate the effects of having a more efficient condenser, try this.
Take your garden hose outside, and with the engine and ac running, hose down the condenser (from the front). The water on the condenser will substantially enhance condensing efficiency. Then go read your pressures and check your vent temps. If they improve to what you want them to be, that's a pretty good sign you need a better condenser.

If you ever have the system open again, think about replacing the orifice tube with a .067 FoundOnRoadDead blue tube. That will help improve your condenser efficiency and reduce your head pressure.
Good luck

 

Thanks for the long and informative reply.

I have tried the retrofit three times carying differant things each time. the first time I had everything apart anyway and did flush the complete system with the exception of the accumulator which i replaced. I have tried the FoMoCo blue orifice and even a Smart VOV http://aircondition.com/vov/

I pulled a 28" vacuum for one hour each and everytime I converted following the instructions.

I had 3 cans R134 the first time and got 50° ducts.

I evacuated and used the smart VOV with 2 cans of R134 and got 50° duct temps.

I evacuated and added 2 cans of an "alternate" blend and got 50° duct temps.

All duct temps were taken at 90° outside air temp. My pressures are high. I can infact take a garden hose and cool the temps while lowing pressures.

I understand that a lower low side will result in lower duct temps but if i only charge to the lowest low side i am undercharged with very little cooling. This is why I am assuming that a parallel flow condenser will help. the only universal ones i seen are at www.ackits.com like the link you posted. making a bracket and hoses are easy for me so I was wondering if this would get me the 40° temps I desire?

I don't have an airflow problem either, I have Spal dual 11" electric high performance fans which pull much, much more air then the stock dual fans ever could. My condenser fins are in decent condition and there is no blockage at all.

 

that's a real stumper of a question you have there...seems like you've covered the bases pretty good.

Have you opened up the AC Evaperator housing and taken a look at the evaporator? 18 years is a lot of time for an evaporator to collect dirt, dust, etc that can come in an unfiltered hvac duct. That could be hampering heat transfer.

Forgive me these suggestions, as some of them are pretty basic ones. Have you readjusted your clutch cycling switch?Have you checked that your heater isn't working against the AC? The heater is a lot more powerful than the ac...it doesn't take much.

With fans like those, that should enhance your condensation as well or better than a parallel condenser. Do you have some sort of seal or weatherstrip between the radiator and the condenser, so that the fans pull through the rad and the condenser, rather than around the condenser and through the radiator?

What do your temps come down to when you hose the condenser? If hosing the condenser doesn't bring the temps down to what you want, than the condenser is not your problem.

 

R134 likes to run a higher hi press then R12. Plus you need less. Reguardless of what you do, it wont be as cold as it was with the R12. I've heard of people using 4th gen condensors, but they need some slight modding where the hose fittings are.

Is it blowing warm just at idle or at highway speeds too?

 

The problems with 134, with our cars, is all in the condenser. The pressure problem is not as big of a factor, as the compressor in our cars (r4's) have the power to reach those pressures. Look up an r4 on acdelco.com, and you'll see the same compressor in our cars being used on full size vans and suburbans.

134 is, in a manner of speaking, actually a higher performance refrigerant than R12. A pound of 134 absorbs 30% more heat when it evaporates than a pound of R12. This would seem to be a good thing...until you get to the condenser. In the condenser, that same pound must give off 30% more heat in order to condense.
There are 2 ways to gain back that cool R12 temperature.

(1) Installing a slightly smaller orifice will reduce the flow of refrigerant, allowing it to spend more time in the condenser, and therefore give off more heat (per pound refrigerant). In theory, if the refrigerant flow rate was reduced 30%, the thermal performance would be comparable to R12.

(2) Improving heat transfer at the condenser. Done either by increasing/improving airflow over the stock condenser, or by replacing the condenser with a unit with greater thermal efficiency. This option has the possibility of actually improving performance beyond that of R12.


Another thing that can help performance at idle is replacing the compressor with one from a truck. The compressors themselves are the same (make sure the suction/discharge ports are the same size as your fittings), but the compressor drive pulley is smaller, which makes the compressor turn faster, relative to engine rpm. Due to the expense and time of compressor replacement, this is really only a realistic option if the original compressor is shot, and has to be replaced anyway.


John-- what alternative blend did you try? I tried some Enviro-safe Industrial 12a the other day, in an S10. I found it's performance to be quite disappointing. The next time I have a vehicle to experiment on, I want to try freeze-12 and see how that works.

 

Yes, the AC evaporator is clean. I had it removed to flush it well.

I have not adjusted the clutch cycling switch, it seems to work fine I guess.

I have not checked to see if the heater door is still opened, i don't think it is.

There is no weatherstrip between the radiator and the condensor.

Temps do come down when i wet the condensor or when i drive. They are in the mid 50° idling a long time when engine coolant gets near 210°. When engine coolant temp is lower I get decent mid 40° duct temps. At highway speeds it cools OK, mid 40°.

I only wish my fan could blow harder too, I can blow harder then it can.

I have a highly modified 383 and make some pretty good horsepower.

I tried the enviro safe on the last attempt, it is still in there. It seemed to work just as good as the R134 (which doesn't work well).

 

-edited-

brain fart question removed - sorry

-Bob

 

Adjust your clutch cycling switch to kick out at about 22 psi. about a quarter to half turn counterclockwise will do it. That won't help your idle temp much (load at idle is usually too great for compressor to cycle anyway), but when at above-idle rpms, it could get you anywhere from 4 to 10 degrees colder.

Is your radiator itself relatively clean? If it's airflow is restricted, that will also restrict airflow through the condnser. With those powerful fans, you should be idling cooler than 210. They should be able to cool your motor down to your thermostat temp.

Your blower fan may need to be replaced. I had one get slower and slower, until it finally quit (in January!! brrrrr). When I took it out, the bearings were so tight I couldn't spin the fan by hand. I put in a new fan, and it blew me away. You might also check the defroster and floor vents. if vacuum doors are leaking to the other vents, that will reduce airflow as well.

Which envirosafe did you use? They have their "12a" in 6 oz cans, and "industrial 12a" in 8 oz cans. I tried the industrial stuff, and it worked worse than 134. From what I've read of the pressure charts, the regular, non industrial blend "12a" might actually cool better.

 

I will try to adjust the clutch cycling switch tomorrow or this weekend.

The radiator is brand new, a Griffin dual 1.25" core universal fit version. It is an awesome radiator. Why do you say I should be idling lower then 210° with the AC on? I do idle at the thermostat rating (depending where I set the fan turn on temp in the prom) with the AC off. With AC on it increases the load and adds heat in front of the radiator. Horsepower equals heat and it must me dissipated somehow.....

I agree the blower fan should be replaced since it barely blows on high. I did replace the original several years ago and it still didn't blow hard like some cars. I bought an aftermarket motor from the parts store. I am looking at different ways to mod the motor with something that blows harder then stock.

I used the 6 oz. envirosafe, I am guessing it is 12A.

 

That's just what I've seen my car, and a few others do. I've got the crummy stock radiator and fans, and I can sit in 90-95* ambient and idle with ac on max load, and my temp hovers right around 180 (my tstat is a 180). My car actually idles cooler with the ac on (because of the electric fans not waiting until 200+ to engage). Granted, my motor is a relatively stock tpi 305, and not a 383, and you're right...horsepower equals heat, but when the throttles are closed and the motor is idling, there's not that much horsepower being produced.

When you adjust that cycling switch, prop the throttle open a little bit to get just over 1500 rpm. If it's at all hot out, the compressor won't be able to pull the low side down far enough to cycle, unless you increase rpm (increase compressor power), or turn down fan speed (reduce heat load).

If it's over 80* out, my compressor won't cycle unless rpms come up, or the fan is turned down one or two notches from high, and my car still has an R12 charge.

I've been lucky so far. 2 of the 3 fbodies I've owned have had working R12 systems (the 3rd one wasn't worth fixing). It's been my experience that they just aren't great at idle. It's been a while since I checked my vent temps. so I don't remember the numbers off the top of my head, but I do remember that bumping the throttle to idle at 1000 or 1200 brought it down several degrees. I didn't even have to drive to get airflow, just the rpms were enough.

Take a measurment when you get the cycling switch adjusted to 22 psi.
On max ac, hi blower, engine at idle, keep the condenser hosed, and measure hi&low pressures, and vent temps in center vents, after the system has stabilized for 5 minutes.

You may want to take the same measurement again, but with the throttle propped open to idle at 1250 or 1500. If that makes a substantial difference, it's possible your compressor might be old enough to have weakened a little.

 

Your right, not much HP is made at idle bit I can assure you a bigger cubic inch SBC with 10.5:1 compression and high performance heads will make lots more heat at idle then a 305.

 

I second that. But even new cars will warm up at idle when its 110 out.

 

Here's another site selling parallel flow condensers:
http://www.acsource.com/index.asp?Pa...S&Category=254