LastBigBlock

All the R134a leaked out of my air conditioning system over the course of about a year, so I decided it was finally time to put in the VIR replacement to try and improve the cooling in my Vette.

I ordered the kit from Classic Auto Air. They sent excellent instructions, but I thought it may be helpful to add my comments.

First step was to remove the splash shield behind the wheel. You have to remove the rocker panel first and I put mine back on the car because I figured this would take a while.

this is what the shield looks like removed:


I then removed to radiator overflow tank. It is very hard to get to the nuts on the inside of the fender, so I epoxied a nut to the lower hole on the tank to make it easier for reinstall. It worked and I wish I had epoxied nuts to all three holes on the tank.

Next step was to take the VIR out. There are 5 tubes or pipes connecting to the VIR, three from the evaporator, one to the compressor and one from the condenser.
Here is a view from below:

And a view from above (took this picture after already loosing the connections):

a couple of the nuts were really loose and a couple were seized up and the o rings were crushed. It is very tight around the VIR so it took a lot of patience to get to all 5 fittings. I had to use adjustable wrenches on a couple of the fittings because they were shorter than my box wrenches.
Here is the VIR removed, rotated around so you can see all the connections:







I then removed the evaporator and cleaned it out, but I posted that in another thread.

Here is the VIR eliminator kit. The Valve in Receiver is replaced with an orifice tube and an accumulator. The orifice tube has 3 connections, in from the condenser out to the evaporator, plus the small oil line in the bottom. The accumulator has two connections, in from the evaporator, out to the compressor. There is also a pressure switch that mounts on the accumulator and a mounting bracket to mount it to the fender. It sounds so simple.

Here is the accumulator assembled as in the instructions. The inlet and outlet are supposed to drop right in where the VIR came out.



First I installed the orifice tube. That shiny stuff in the bottom is the aluminum foil I put over my evaporator connection to keep it clean:



Next came the fun part. I put the accumulator in and connected the 90 degree elbow in the top to the evaporator top tube outlet. The elbow is the part connected to the dirty evaporator outlet which turns into the top of the accumulator. It is hidden here by the heater hoses:



I then attached the accumulator to the fender just underneath the radiator overflow tank. I had to flip the bracket over from the previous picture of the accumulator. I had to take care to make sure it was low enough for the overflow tank to clear the top:



When I went to hook up the outlet of the accumulator to the compressor inlet, I discovered that the 180 degree turn in the old fabricated hoses was too long to fit in the space above the #1 body mount cushion.

Took a break and ordered a new muffler compressor hose assembly which goes into the back on the A6 compressor and out the back of the compressor to the condenser. When I tried to connect that 180 degree connection to the outlet of the accumulator, I discovered that the 180 degree connection was turned in the wrong direction to make the connection to the tube coming out of the bottom of the accumulator:



I could not figure out how to get it to work, so thought seriously about going back to the VIR. I was extremely frustrated. Also thought about bending the tube from the bottom of the accumulator, but could not figure that out either. There was no way to get the kit to work with the standard hoses, as provided. What I decided to do was to cut the compressor inlet hose and install an elbow directly into the bottom of the accumulator. Took another break and ordered the connections needed from a local hose shop. Here are the before and after. This is my original section of fabricated hose next to the purchased hose set:



This is the purchased hose set after modifying to attach directly into the bottom of the accumulator. Note the coupling and the elbow:



The elbow worked great. Got it in place no problem and discarded the crazy tube previously coming out of the bottom of the accumulator:



Recruited my son to help me remove the hood and hooked up the outlet hose on the set from the compressor to the condenser:



Ran the vac pump for 30 mins, achieving 30 " Hg vacuum, let it sit for an hour then put the hood back on.



Most uncertain part of the project for me was tightening the fittings to "10-15 foot pounds, or 1/4 turn past hand tightened." What the heck does that mean when most of the connections were so difficult to line up and then to even get the threads started right, there was no chance I could get far hand tightening, much less gauge 10-15 ft lbs.

Charged the system with around 40 ounces of R134a. I jumped the compressor off of the alternator for a few minutes until there was enough pressure so it would run on its own. It was 90 degrees in the garage and my pressures read 50psi low side and 350 psi high side.

I did somehow blow the fuse to the high speed wire to the blower relay and my blower relay seems to be messed up now. Not sure what is going on there, but it is hanging up and not shutting down when I kill the ignition.

Air is blowing about 30 degrees below ambient. Took a Sunday afternoon ride today and got 57 degrees a the dash with 87 degrees outside.

The system is still not as cold as I would like, but I am done with this for a while. I think I need to get another C4 blower to increase fan speed. I had used a late C3 motor with the C4 squirrel cage, but not sure it is as fast as the complete C4 motor and fan. If anyone knows this detail, please comment.

One detail on the installation said that the screw in the center of the cycling switch should be turned 3/4 counterclockwise if using R134a, which I did. I read a lot about compressor cycling, but I guess it has been so hot here that it has not cycled yet while I have been driving. I guess that will happen when cooler weather comes to lower the pressure going back to the compressor. I might be missing something here.

Any input or advice to further tweak my AC would be much appreciated. I will make notes, but need a break and to move on to another part of the car for a while.

Thanks for reading,

Don

persuader

Good job Don when i was redoing my entire engine bay on my 77 I new I would have to tackle this same dilemma. So I instead of going with a VIR eliminator kit I decided to upgrade my system to the one found on 79 and up. First thing I did was install a C4 blower assembly without using a spacer, I instead extended the blower housing about 3/4 of an inch. Then I switched out the original evaporator for one out of an 81. Although I as of yet to finish up the conversion, all that is left is to put in the accumulator and the hoses and line from an 81 and I will be done. I do plan on using a sanden compressor instead and a parallel flow condensor. I fully expect my system when done to be light years colder than I would have gotten by just going the VIR elimination route. Or not...we shall see. Rich

LastBigBlock

Rich,

thanks for the encouragement. I think extending the housing for the blower instead of just adding the spacer may be key to max airflow.

Also, does the 81 evaporator fit into your '77 evap housing? What is the difference between the two?

Keep working on it. Would love to hear what your temps are when you are done.

thanks,
don

persuader

Here a some pics. Having a problem with my pictures lately. Cant seem to get them right side up.

persuader

The 81 evap fits like a glove. Bolts in just like the one i took out that just like yours , Had three hard lines coming out of it.

LastBigBlock

Rich,

i like what what you did with the blower housing. You have some skill with fiberglass.

thanks for the info. Will add to my future projects list when I break into the AC again.

i think you will be freezing with your system. Well done,

don

REELAV8R

One of the secrets to getting cool AC from the orifice tube system is using the correctly sized orifice tube.
The ford blue or the ford red are reported to work far better than other orfice tubes. Blue is .067 and the red is .062.
do a google search on these tubes and the results people have gotten from them. Check out the ford forums or an automotive ac forum for more info.
Here is a chart with the color and size of the orfice;
http://www.aircondition.com/tech/que...be-Color-Chart

Notice that the GM orifice tubes are white or white/black and have a .072 sized orifice.

Since the way cooling is created is via the pressure difference in high to low the smaller orifice will create a greater pressure difference giving you better cooling.

The smaller orifice is going to perform better at idle RPMs but also create more restriction in the system, and the larger orifices are going to perform better at cruise with less restriction. Typically idle RPM and therabouts is where the problem lies since at speed we have plenty of air going through the condenser to keep it cool.

Your 50 psi on the low side is pretty high and is probably why you have high duct temps. You should be running 35 to 40ish on the low side.
What color was the orifice tube included in the kit?

Also if you have not already done so blocking off both of the heater hoses with valves keeps the heater core isolated from the cooling system and not adding heat to your duct temps.

Great write-up by the way.

persuader

Thanks for posting this info. I will be refer to this as I go forward with my conversion.

LastBigBlock

Reelav8r,

Thanks for the AC education and link. I need to do a lot more research, as I just started with a plug in of the supplied kit. I did not notice a color on the orifice, it was just a machined aluminum block from what I remember. I will write to Classic Auto Air and ask, but assume it was just the later model Corvette orifice which I assume is the .072" based on your note above.

I am definitely interested in downsizing to increase the pressure drop and help in around town traffic where I have the biggest cooling problem.

Also, I have a hot water cutoff valve on the supply side coming out of the manifold to the heater core. Why would I need one on the return line if there is no flow. I just assume my heater core is filled with stagnant water while the one valve is closed, but might be missing something.

Thanks for the help,

Don

LastBigBlock

Rich,
your pictures showed up right side up on my phone when I first viewed them. Now they are sideways and upside down on my computer. I have the exact same problem when I try to post pictures and have started taking all of them holding my phone in the exact same (upright) position each time which is the only thing I can do to get them right on the computer.

after looking at your evaporator housing on the computer I am really impressed with your work. it is a beautiful thing.

Don

chevymans 77

Good write up, thanks

The fixed orifice is not optimal for a system that has a variable flow as the engine driven compressor. The VIR has a TXV and a POA valve that will maintain a consistent evap coil pressure and temperature through out the operating conditions, it can optimize for idle and cruise. GM designed the CCOT system to be optimized at around 1800 rpm's cruising with decent air flow through the condenser, out side of this and the system performance deteriorates some. With r134a your condenser is not optimal you need to consider going to a cross-flow condenser that is designed to work with 134a.

Pressure drop is only part of the equation when it comes to getting the system to function as intended. The orifice has to be supplied with a good quality supply of liquid, not a mixture of liquid and vapors. This is the job of the condenser and a correct charge. The evaporator pressure is critical to getting cold air temps from the vents as long as the system is working correctly. With the fixed orifice it is impossible to maintain a constant evap coil pressure as engine speed changes.

The correct way to charge is to set the system to recirculate with the fan on high and the doors closed with the engine at around 1500 to 1800 rpm's. Set a good strong fan in front of the car blowing through the condenser. Monitor the blower inlet and vent outlet temps shot for the maximum DT. Try and set the suction pressure around 28 to 30 psi with the above conditions and the interior temps in the lower 70's. Remember that as the interior temps drop so should the suction pressure.

I agree with REELV8R it sounds as if you may be a little over charged,

Your system should work very well once the charge is correct, even with the original evaporator coil.

Neal

LastBigBlock

Neal,

thanks for the info. I did not understand the details before jumping into this conversion and was looking for something more "reliable" than the VIR. Not sure I went the right direction with the fixed orifice, but I appreciate your help in trying to make the most of it.

i charged my system with 2 lbs 8 oz of R134a and took pressure readings at idle (600 rpm). I will take readings again with the fan blowing into the front and the engine at 1500-1800 rpm.

i think what you are saying is I should let refrigerant out of the system until the low pressure drops into the 30's? while monitoring the temp drop, blower inlet to vent. Do I understand this correctly?

concerning the condenser, I get that I need to make sure I have liquid going to the orifice as much as possible. Do you know of any suppliers the produce a drop in parallel flow condenser for a C3? I really want to avoid modifying the condenser mounting hardware if possible.

thanks for the help,

don

REELAV8R

Heat still gets to the heater core via convection. The heat from the cooling system will eventually heat up the core since the coolant in the heater core is still in contact with the cooling system coolant.
Try this, go for a drive for about an hour. Then put your hand on the plenum that the heater core is in, down on the passenger side near the passenger's feet. It'll be hot, not cabin temp.
On my 77 I initially blocked only one hose as well. My wife complained of heat near her feet after driving for a prolonged period. Sure enough it was hot on that plenum. so I installed a second valve in the other hose and heat is now gone.

I have good floor insulation so engine heat from the floor is not a factor. This may have made it easier for me to detect where the heat was coming from. If you have a lot of engine heat coming from under the floor, you are still fighting that heat in the cabin but it should not affect duct temps.

Sound about right on the quantity of 134A. If you are still using the stock fan assembly then yes you will need to idle it up to get usable readings. Air flow through the condenser is vital for function of the system.
Putting in more 134a would likely make things worse. If you let some out then you will have to check the operation of the pump at a higher RPM level , 2500 to 3000 to simulate cruise performance.
As the RPM's go up the low pressure drops. If it drops below the preset low pressure sensor's acceptable level then the clutch will cycle off. This is a low freon charge symptom and is what the low pressure switch is supposed to do to insure adequate lubrication to the pump.
Once you let some 134a out you loose the ability to know how much 134a is actually in the system and then have to depend on system pressures to insure proper operation.

As chevymans77 stated another secret to the 134a system is a parallel flow condenser. Although I have not done that to mine and it performs well. I do have high flow dual electric fans however. So even at idle I have a high flow of air across the condenser.

Red86Z51

Hi Don,

GREAT detailed write up!

Have you considered using any other alternate refrigerants? From everything I've ever read, R134a never cools as much as most who have converted their systems would really like. Many moons (and cars) ago, I started replacing R12 with Enviro-Safe Industrial, and I am currently using it today in my '74.

Let me begin by saying; Yes, it IS leagal to use in your car. Yes, it IS a hydrocarbon refrigerant (propane/butane mix). No, your car will NOT blow up on you, your insurance will NOT drop you, your dog will NOT bite you, and your wife will NOT divorce you. In fact I think my wife loves me more since I switched than before, because she now runs a heck of a lot cooler when we go out.

I get center vent temps of 38º to 40º with high humidity and 85º to 90º+ outside temps, and the fan setting on 3. The vent temps have actually dropped to 34º on those days when I set the system to MAX (inside air recirculate). My system is still the VIR with the original A6 compressor. I did reseal the shaft on the compressor using the double lip seal...but that's the only "mod" I made.





The Enviro-Safe is compatible with all oils, and you actually charge the system when it is at atmospheric pressure (no vacuum). One 6oz. can replaces 18oz. of R12. My pressures do run lower too...High side runs at 225psi, and low side runs at 40psi.

Here is what I have been using for years with no issue:





I just wanted to share my experience with this refrigerant with you. And no, I do not own stock in the company...I'm just a very happy (and cool) customer!!

Dave

REELAV8R

Hey Dave, funny you should bring this up. I nearly pulled the trigger on that stuff just a few weeks ago. Normally my 134a system is ice cold but this year we got lots of humidity at 95* to 105* and the best the 134a could do is a 60* duct temp. It's on par with what it's supposed to do but I was wishing I could get a lower duct temp on those days.

You used the industrial vs the standard refrigerant? Did you add any of the special "air enhancer" oil they sell?

LastBigBlock

REELAV8R,

Thanks for the additional info. I need to improve floor insulation and will also check out the heater core area temp to see if that is a problem. Adding the second valve is an easy fix.

Thanks for the warning about letting the pressure get too low as I let refrigerant out. Will check at higher RPMs as I go.

Much appreciated,

Don

LastBigBlock

Dave,
I have not considered other refrigerants, but appreciate the education and your experience with Enviro Safe. I would especially like to make my wife enjoy cruising more in a cooler car. I might not get to drive it much anymore if I get it as cold as yours!

I really like that 38 degree thermometer pic. Impressive! If I cant get an improvement tweaking with R134a, I may go that route.

Are you still using the original cross flow condenser in your system, or did you install the better cooling parallel flow design?

Thanks for the input,

Don

Red86Z51

Yes, it was the industrial I used. I didn't use anything special at all, just the correct amount of mineral oil for the original R12 system.

Since you've converted to 134a and have already added the PAG or ester oil, there is nothing you would need to do except void the system of the 134a and recharge with the Enviro-Safe...it's compatible with all oils. Just remember, do not charge the system with vacuum pulled, add the Enviro at atmospheric pressure. Unlike R12 or 134a, that refrigerant is not corrosive when exposed to moisture.

For obvious reasons, I've been very happy with that product!

Dave

Red86Z51

Hi Don,

My bride won't drive ours...she's afraid that if something is going to happen to it, it will be on her watch!

I'm still using the original tube and fin condenser. In fact, everything on my system is original, right down to the VIR. If you're using a parallel flow you may have to reduce the amount of the Enviro-Safe you use. I had an '87 whose condenser got a hole punched in it and I changed from the original tube-n-fin to parallel and actually had to slightly reduce the amount of refrigerant in the systems to dial in the pressures. That was another car that got equally as cold.

Dave

REELAV8R

I talked to someone over at Enviro-safe, don't remember his name, used car salesman sort of personality, and he said the same thing about not pulling a vacuum. He did say that if I needed to pull a vacuum however to use the industrial version of the refrigerant.

So you used the industrial with no vacuum and it's working out, that's good to know. Thanks.