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Old 07-13-2008, 06:56 PM
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134a questions, I've searched and I've read

a lot of threads on converting to 134a and a lot of threads appear to be a year or two old. So what is the best way to convert a R12 92 Chevy S10 to something else.

The system was open for about two years but all connections were covered with plugs or tape. I believe the system is clean but not sure how much oil remains.

I've replaced the condenser and all the lines. I've replaced the orifice tube and the accumulator/dryer. The compressor and the evaporator are the only two parts of the system that remain that may have some old oil.

I have pulled a vacuum on the system to about 29" on my old gauges. Left it bottled up for two hours and 21" remained. So, I think I got a system that will hold a charge.

Should I flush the evaporator and take the compressor off and dump the oil out of it. Some of the oil has run out of the compressor during the two years of being apart.

Also, what's the verdict on the Freeze-12, Duracool, etc. replacements. Or should I just stay with 134a?

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Old 07-13-2008, 08:12 PM
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First off, do not use any R134a substitutes, that's just asking for trouble. If it were mine I would flush the evaporator and get a new or rebuilt compressor. You can never get all the old oil out of the original compressor and any remaining oil will not mix with the oil required for 134a. Some will say that old oil will just pool in the bottom of the accumulator and won't harm anything, don't believe that . The system should hold vacuum for longer than 2 hours.

I converted my 90 Chevy truck about six years ago and replaced everything but the compressor, evaporator and condenser. It worked fine for almost six months then the compressor puked. I got a reman compressor from Autozombie and the system has worked fine ever since.

Vince
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Old 07-13-2008, 09:06 PM
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Quote:
Originally Posted by 302 Z28
First off, do not use any R134a substitutes, that's just asking for trouble. If it were mine I would flush the evaporator and get a new or rebuilt compressor. You can never get all the old oil out of the original compressor and any remaining oil will not mix with the oil required for 134a. Some will say that old oil will just pool in the bottom of the accumulator and won't harm anything, don't believe that . The system should hold vacuum for longer than 2 hours.

I converted my 90 Chevy truck about six years ago and replaced everything but the compressor, evaporator and condenser. It worked fine for almost six months then the compressor puked. I got a reman compressor from Autozombie and the system has worked fine ever since.

Vince
How do you suggest flushing the evaporator?

I have no problems getting a new compressor and using 134a. I was just wondering is there was any new experience good or bad with the other replacements.

Are you speaking from experience with the other replacements?
Thanks for the reply.
overdriv
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Old 07-13-2008, 09:37 PM
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Quote:
Originally Posted by Overdriv
Also, what's the verdict on the Freeze-12, Duracool, etc. replacements. Or should I just stay with 134a?
Check the EPA website for lots of information.
Duracool is not legal in the USA for cars, but it is works great. It is in political limboland. It's status is undetermined, therefore not approved.

On the EPA site you will see that Freeze 12 and Freezone are 80% 134 and 20% 142. which reduces the pressure curve and increases cooling. Comparable to 12.
You MUST add 134 oil to those systems or the oil will not circulate and the compressor will fail. I saw several do it.

That said, my buddy has a converted Freeze12 system with 160,000 miles on the compressor. Buick V6 with that flat compressor. All he did was dump in 6 oz of 134 oil and charge it up, no flushing. It is as cold as the 12 system and has been humming for 4 years and 80,000 more miles.

I've seen 134 systems converted to Freeze12 and they are colder.
I intend to use Freeze12 on conversions because it is colder than pure 134.

I have one car getting two condensors in series and Freeze12. Sucker WILL cool in traffic or else.
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Old 07-14-2008, 05:37 AM
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There are flush kits available for cleaning out the condenser, evaporator, etc. Check Autozone... they show one in the loan-a-tool program. Don't forget to replace the accumulator... the dessicant used for R12 isn't compatible with R134a.
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Old 07-14-2008, 08:18 AM
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If you convince yourself to go with any of the R134a alternatives, I suggest you first check with some professional AC technicians and get their opinion.

Duracool is hydrocarbon based, that means it is flammable containing isobutane

Freeze-12 is 80% R134a, why not just use R134a?

Vince

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Old 07-14-2008, 09:05 AM
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It used to be that you could use R-11 to flush a system. Someone recently told me that he uses brake cleaner, supposedly the kind he uses is poured into the system then blown out. It evaporates quickly and will be totally gone when the system is evacuated. I don't think I'd put that through my vac pump though!

I put R-414-B into several cars with good luck and one guy used propane successfully. Yes, I did say propane. Never tried that one either!
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Old 07-14-2008, 09:11 AM
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Anhydrous ammonia can also be used as a refrigerant and is in some industrial applications. Do we really want propane, isobutane or even ammonia being sprayed out when a hose burst? For heavens sake people, use the right stuff in the system, there are no long term viable shortcuts.

Just my 2
Vince
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Old 07-14-2008, 09:33 AM
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Like anything, there is the right way, the wrong way and the way your boss told you to do it.
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Old 07-14-2008, 10:25 AM
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Quote:
Originally Posted by 302 Z28
If you convince yourself to go with any of the R134a alternatives, I suggest you first check with some professional AC technicians and get their opinion.

Duracool is hydrocarbon based, that means it is flammable containing isobutane

Freeze-12 is 80% R134a, why not just use R134a?

Vince
The free flash point of 134 is actually lower. Check the EPA site. Most people don't realize that 134 will explode too.

The blends lower the pressure curve by not going nuts on the high pressure side when ambient temps exceed 90*. That's why a high cut off switch is mandatory, to keep from blowing up the system. Those blends cool much better at lower rpms, vehicle speeds.

The blends' high side operating pressures are much less. Also 134 loses efficiency at high ambients, that's why they have a humongous high efficiency condenser with all those little tubes and fine fins.

IF you choose to replace your condenser with a high efficiency unit designed for 134, then you can maintain more cooling capacity. If you stay with the 12 condenser and use 134, you can expect that the vent outlet temperatures will be 20* higher than 12 at slower speeds in town...... just when you want it the most.
Get in a hot car and drive across town? Expect to sweat. Converted 12 to 134 just won't cut it if you are used to 12.

134 is very efficient...... IF you can keep it cool. That's why the humongous new condensers on newer vehicles, and why mine is getting dual condensers.
Ever look at a new style condenser in a new pickup. what a whopper for a little cab.
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Old 07-14-2008, 03:15 PM
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Lots of different opinions and some conflicting info. According to EPA web site Freeze 12 is legal and safe to use. But it's a moot point around here as no one has it, most have never heard of it.

SO, I've decided to go with 134a. But Autozone has something called 134a with "Sub Zero". Has anyone used this stuff? Does it do what they say it does?

I've got the Evaporator flushed out and dryed. The new compressor will be here tomorrow. The entire system will be dry, no oil of any kind anywhere, unless the compressor will have some in it. I think the system takes 8 oz of oil. Should I put a couple of oz of oil in each part of the system as I'm putting it all together? Or how is the best way to put oil in the system.

Now, since the capacity of my system is not stock, (custom length hoses, shorter), how should I charge the system? By the pressures or certain quantity, which I'm not sure how to figure with the shorter hoses. I know the rule of thumb is 10% less 134a than R12.

Any suggestions will be appreciated.
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Old 07-14-2008, 05:49 PM
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Says it's 11oz of 134a and 2oz synthetic AC booster , whatever that is. I'd be a little skeptical of it myself.

update: Here is the MSDS sheet on it. Must be just R134a and a shot of synthetic oil. I think I would stick with plain R134a and add the specified oil myself.

Vince
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Old 07-14-2008, 09:14 PM
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I converted my '75 GMC (SBC 350) using a new Valeo compressor and an aluminum parallel flow condenser from Arizona Mobile Air. I also used a smaller orifice (Ford Blue) and replaced all the hoses with new barrier hoses. I added a high pressure cutoff that kicks in at about 300 psi. I used PAG oil that was pre-loaded in the new compressor. The original evaporator was cleaned with A/C flush, and the accumulator was replaced. I am using a stock steel fan with an HD thermal clutch, and the stock fan shroud.

My system works best when charged with R134 to 75% of the original R12 charge. With this combo my vent temps are about 35 degrees with an outside temp of about 85-90 degrees.

Bruce
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Old 07-15-2008, 08:46 AM
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Originally Posted by 75gmck25
My system works best when charged with R134 to 75% of the original R12 charge. With this combo my vent temps are about 35 degrees with an outside temp of about 85-90 degrees.

Bruce
Fifty? degrees delta drop? is outstanding.
How did you accomplish that?
Is this idling or running down the highway?
More details please.
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Old 07-15-2008, 09:58 AM
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Quote:
Originally Posted by 75gmck25
I converted my '75 GMC (SBC 350) using a new Valeo compressor and an aluminum parallel flow condenser from Arizona Mobile Air. I also used a smaller orifice (Ford Blue) and replaced all the hoses with new barrier hoses. I added a high pressure cutoff that kicks in at about 300 psi. I used PAG oil that was pre-loaded in the new compressor. The original evaporator was cleaned with A/C flush, and the accumulator was replaced. I am using a stock steel fan with an HD thermal clutch, and the stock fan shroud.

My system works best when charged with R134 to 75% of the original R12 charge. With this combo my vent temps are about 35 degrees with an outside temp of about 85-90 degrees.

Bruce
Where did you install the high pressure cutoff switch?

Why a smaller orifice tube?
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