Help with R406a
 

I have converted the ac system to autofrost and went back to the dealer to get the original r12 high and low side valves. I Cant find an adapter that will let me connect to the high side.
I have a new set of r12 Yellow Jacket gauges that didnt come with any adapters. I found one that you can see in the pics that allows me to thread onto the fitting but it doesnt open the valve so I can't get any readings.
The ac is absolutely amazing by the way. As you can see the accumulator is icing over. Idling in my driveway on a 105 degree day and its blowing 40 out of the vents.
My concern is the low side is reading 75-80 psi all of the time and never comes down. I know that isn't how it should be and I can't check what the high side is running at.
I did install a variable rate orifice tube if that changes anything. Condenser, compressor, lines, and accumulator are all new. The only thing reused was the evaporator.
Anyone know how to procure the fitting i need?

Re: Help with R406a
 

You need a 3/16th on the high side port that connects to the 1/4th on your red hose. The adaptor piece will say R410a (at least mine does). Regardless, it does the job.

I use this one:
http://www.ebay.com/itm/Flex-Hose-3-16-FM-Flare-R12-High-side-x-1-4-MF-/150657309515?vxp=mtr&hash=item2313e01b4b

Re: Help with R406a
 

Are your radiator fans both turning on?

Did you vacuum the system?

How much R-406a did you put in?

Something seems odd to have frost with 75 psi. At 75 psi, you'd normally be getting about 70° air or something around there blowing out the ducts. In other words, hardly any cooling at all.

Re: Help with R406a
 

Just the man I was hoping would respond!!
Thanks for the fitting info.
I've got both fans on as well as a pusher fan running.
I vacuumed the sys for 2 hours.
I put in 29 oz by volume of 406.
I agree it is strange but I sure love the ice cold air!

Re: Help with R406a
 

Just ordered that hose!

From the info I could gather it looks like either the orifice tube is malfunctioning or the compressor is.

Re: Help with R406a
 

You and I both have different weather conditions that make Autofrost a lifesaver. Me with my atrocious Texas humidity and you with your Arizona insane heat. I've found that stepping out of the car after arriving somewhere, that that wallop of heat upon opening the door is quite powerful.

Can you take a picture of your manifold gauges and use MS Paint to draw a line to where you're getting the 75 psi reading at? I'm wondering if it could be something as simple as reading the wrong scale on the gauges.

What condenser did you end up using? Seems that most of the condensers for our cars always have the wrong size fitting on them.

Regardless, I'd like to see what the low and high side readings are showing up as. 75 psi just doesn't seem to make sense. These cars run 110 psi just sitting there with the engine off and nothing happening.

Re: Help with R406a
 

I'll put the gauges on it once I get that adapter in and will take a pic of them with the ac running.

Re: Help with R406a
 

Am I understanding the AutoFrost conversion correctly? Basically, evac old stuff and put AutoFrost in. Nothing more to do? Or is there some calibration/new switches that need changed?

(BTW, read the orginal review thread on this and saw someone worried it might be gone in a few years, that was 2007, great to hear it is still around!)

Re: Help with R406a
 

Actually they aren't making it anymore there is just leftover 406a on the market still for sale. But when its gone its gone.
The conversion is a little more complicated. You have to flush ALL previous oil out and replace it with mineral oil. Then add the 406. No real extra stuff to speak of. Just a thorough cleaning and recharge.

Re: Help with R406a
 

[QUOTE=
What condenser did you end up using? Seems that most of the condensers for our cars always have the wrong size fitting on them.[/QUOTE]

Spectra Premium 7-4426. It looks like it might even be a parallel flow one. But I couldn't tell for sure.

Re: Help with R406a
 

I am having great luck with R152a!

Re: Help with R406a
 

If the car is still R-12, it will already have mineral oil. So no need to change oil. If it has R-134a, then yes, you'd have to flush all the PAG out of the system. R-406a will work in POE oil, but mineral oil is preferred.

The adjustable low pressure cycle switch that is attached to the accumulator can be left in the stock setting. (Aprox 25 psi). No need to adjust it lower like on R-134a conversions. With the stock 25 psi setting, the compressor cycles off when duct temps are around 30-31°F. I've tried adjusting it down to cycle off around 27° and even went as far down as 24°. But wound up changing it back to stock. Reason being

a) 31° is damn cold already. There is no need to go any colder. Any humidity in the air is long gone. In fact, the dew point at 31° is roughly the same amount of dryness as Phoenix is during the summertime (115°/6% humidity = 31° dew point). This is worlds away from Houston's outdoor dew points in the summertime (75-80°F)

b) Waste of fuel to cool into the 20's °F

c) Part of me worries about the plastics and dash being subjected to below freezing temps and then back to above freezing. Back and forth, back and forth.

d) At 24° you've got a snow white accumulator and refrigerant line running to the compressor. I found that it would suck the insulation off the hood and stick to the accumulator. At 27° you'd still get a bit of insulation sticking to the accumulator. At 31°, it's just wet but not sticky. So the hood insulation stays on the hood.

e) Why push the system harder than it needs to. At 24°, my hands went numb and my arms started shaking from the cold.


At 25 psi compressor off cycle, you get duct temps of:
R-12 = 35°F
R-134a = 39°F
R-406a = 31°F

So you can see why R-134a conversions recommend lowering the low pressure cycle switch down a few psi. This works OK during the fall and spring, but will have trouble even reaching 25 psi let alone 22 psi during summertime.

Honestly, the sweet spot is when the duct temps are in the 31-35°F range. Once you get down to 35°, the air starts to feel thick and denser. Like taking a deep breath outside in wintertime. You quite often need to turn on the windshield wipers to clean the condensation off the outside of the windshield when you get down here. Especially at night.

Re: Help with R406a
 

Thats a great problem to have!! This is the first camaro I will have that has ac that blows lower that 50 degrees.

Hey Reid I got the adapter line and That didnt do the trick either. My issue is that the button to open line in the valve is a good 1/2 inch into the fitting. Its not right flush or even close to the top of the high side fitting. Here is another pic.

Re: Help with R406a
 

Ok. Ive got some updates.
I found the adapter I needed. Robinair Fitting # 18143 A/C Access Valve Adapter.
The compressor pressure releif vavle opened up and blew out all the freon before I had the adapter.
So I bought a new compressor and a Ford red orifice tube to start getting rid of variables.
Installed them both this morning and put an 80% charge of 2.25 lbs of 406 in it.
The gauge readings I got when I started the car were still not where I expected them to be so here are some pics of the gauges.
Currently it is 70 degrees outside and humidity at 44%.

As you can see the accumulator and low side line are icing over and the ac feels amazing but form my understanding the low side pressure shouldn't be where its at.

Any Ideas?

Re: Help with R406a
 

Bringing this one back from the dead. Its getting hot again and I blew out another compressor. So I got another one GM PN 88964863 and put a white orifice tube in just to remove variables and replaced the high pressure switch on the back of the compressor.
I'm getting the exact same results.... AC is nice and cold but will never cycle because the low side never draws down below 70 psi. The high side slowly climbs from the 150 psi range as the car warms up to about 250 psi. Which is where I left it last year and on a hot day driving down the road it will blow out the relief valve on the back of the compressor and game over. So I don't know exactly what the pressures were right before the blow up.

I have researched and researched and what I have found from a GM service manual is a bad orifice tube, bad compressor, or low charge. Tube and compressor have been changed twice now and using a charging cylinder I charged it to 36oz by volume which is exactly what it is supposed to have with r12.

So I am out of ideas. Does anyone have any suggestions?

Re: Help with R406a
 

Is the charge for R406a one-to-one with R12? IOW, if the system requires 36oz. of R12, is 36oz of R406a required as well?

Re: Help with R406a
 

I have a charging cylinder so I was able to measure out the volume of 36 ounces of R12 and put in the exact amount of 406 by volume. I'm not really explaining it well but it wasn't really 36 oz of 406a. It was the same amount of R12 in volume rather than weight.

Re: Help with R406a
 

Does anybody know at what pressure the relief valve blows on the back of these R4 compressors. Cuz that's what keeps happening.

Re: Help with R406a
 

No. R-406a requires 80% of the charge that R-12 was. So in my car for example, the original R-12 amount was 2.25 lbs (36 oz)......Putting R-406a in, you would put in 28.8 oz.

If you have 36 oz of R-406a, you are overcharged. This will make it harder for the low side pressure to come down to cycle off point (25 psi) as well as push the high side pressure higher than it should be. Normal high side pressure for R-406a is roughly the same as R-134a during summertime (250-300 psi) depending on traffic, ambient temp, and humidity.

However, R-406a should actually send more heat out of the condenser than R-134a due to 406a being a blend. (More of the condenser has a phase change occurring than 134a would due to the blend having multiple temperature phase change points. 134a only has one temperature phase change point. Thus less of the condenser is actually being used at any given time).....This is part of the reason that R-406a works so well. It's maximizing the efficiency of the condenser at all times. Single refrigerants like R-12 and R-134a are bottle necked by the condenser.

Cars makers in general have gotten around this by having better and bigger condensers (like parallel flow) installed at the factory along with higher flow (noisier) radiator fans.

Re: Help with R406a
 

425 psi rings a bell for me, though I can't say for certain. I'm not sure if that's the high pressure cut out switch or the blow off valve.

Re: Help with R406a
 

I've charged it with 28.8 oz before and had the same results. But there as been a development since my last post.

I charged it again with 36 oz. and then for kicks tried a different set of gauges....... My brand new manifold low side gauge is bad!! I turns out I had the cycle switch dialed it to not turn off before like 5 psi on the low side. So the thing constantly ran.
I dialed it in to cut out at 25 psi and everything seemed perfect. It was cycling on and off now with the high side never hitting 250 psi.
I took it on a test drive and after 10 minutes of driving the pressure relief blew out again. ugh!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I have ordered another pressure relief valve as well as a new accumulator because I found other threads saying that moisture in the system can cause high head pressure.

So, this week I will put it together once again and hopefully with your (Reid's) advice using an 80% charge and working gauges this project will be done with! it makes me sick that I have lost so much 406A!

Thanks for the help!