VIR Rebuild Kit

[dannygila]

Hello All,
In a former post, I was gathering advice on how to attempt to revive the R12 air conditioning system on my 1976 Fleetwood Brougham. I am one step closer in that I determined the system does hold a vacuum. One piece of advice was to change the desiccant bag in the VIR before charging. I just ordered a VIR maintenance kit from Original Parts Group which includes the desiccant bag, various size o-rings and a few other little parts. My questions are: Is this a simple job, or does it require advanced automotive skills? Should I just replace the bag, or go ahead and use all the parts in the kit? Any "how to" or "be careful of" advice is greatly appreciated. Thanks.
-Dan

["Cadillac Kid" Greg Surfas 15364]

Dan
Holding a vacuum does not tell you if the system will hold pressure without any leaks. Remember, when operating the system is under pressure up to and over 300 psig.
Now regarding the VIR, there were two systems used in 76. The VIR and the EEVIR. The difference being the TXV and POA capsules as well as the ports in the central body. You don't say it the system was working or not at any time in the recent past. Changing the dissacint bag will give you a good idea about the condition of the system regarding debris or sludge, so pulling the lower tank (receiver) would be the first step. To pull the TXV and the POA capsules without damaging them requires a special tool as shown in the factory service manual, so you have to add that into the equation regarding the depth of "refurbishing" you want to go to.
At$110.00 per pound, going wholesale price for R-12, it you put the system together, charge it and the VIR doesn't work recycling the refrigerant is a must.
Short version is that buying a rebuilt VIR from a reputable supplier would be my suggestion.
Greg Surfas

[dannygila]

Thank you Greg. The AC was not blowing cold when I bought the car. The system is totally empty as of now. Do you happen to know where or who sells rebuilt VIRs for an almost fifty year old car? Is there a way to tell if it's a VIR or an EEVIR? Here are a couple pics of the unit.

["Cadillac Kid" Greg Surfas 15364]

Differences are internal. Try old aire in Ft. Worth.

[Seville Life]

Greg since when wasn't holding vacuum a sign the system would hold pressure?

ALL manufacturers and re-charge companies use holding a vacuum for a period of time as a precursor to administering a new charge of refrigerant?

Is there some other test we've never heard of that you use?

I'm familiar with VIR that appeared in '73, what is EEVIR? Paul

["Cadillac Kid" Greg Surfas 15364]

Paul
The EEVIR (Evaporator Equalized Valve in Receiver) is just a modified (and substantially cheapened) VIR.
The difference is in the body circuiting and the TXV and POA capsules.
The joints on automotive AC systems seal with O rings. Under vacuum the o rings are "sucked" into any openings that may exist sealing them off. When the systems are under pressure the o rings blow out (if the joint is not correct) and leak. drawing and maintaining a high vacuum for extended periods is to remove and air and "boil" away any moisture in the system before charging it.
Leak detection has been and is done with everything from soap bubbles to Halide leak detectors, to electronic leak detectors capable of detecting leaks on the order of ounces per year.
Greg Surfas

[Seville Life]

Thanks Greg

When did the EEVIR appear then? I ask because we ran several '73 Cadillacs, the start of VIR up to '75?

I then moved to a '78 Seville obviously with fixed-orifice.

Do you have experience of these non-standard fixed orifice tubes designed for hotter locations? Some they work others say they cause other problems with your refrigeration system?

Paul

[Chopper1942]

Usually the outlet temp, with recirc on, windows closed, is 30-35 degrees less than the ambient temp with 20-25% humidity.  If the humidity is higher, the outlet temp will be higher. For example, at 70 degrees and 25--% humidity the outlet temp will be 38-38 degrees.  The orfice tube controls the amount of high pressure, high temperature liquid refrigerant that enters the evaporator.  If the orfice tube allows more refrigerant into the evaporator, all the liquid refrigerant may not vaporize and then enter the compressor and can cause damage to the compressor. What actually controls the outlet temperature is how well the doors in the HVAC box seal, water drains from the evaporator, air flow across the evaporator, the low side pressure.  On a clutch cycling system, the low side pressure is controlled by the clutch cyclying switch.  Depending on application, the switch turns the compressor off between 30 & 35 psi on the low side.  If the low side pressure is pulled down to 30 psi, the temperature of the evaporator is 30 degrees.  If it stays at 30 psi for any amount of time, the water that condenses on the evaporator will freeze blocking air flow through the evaporator causing higher outlet temps and lower air flow. When the low side pressure rises to 10-120 psi on the guage, the compressor will come back on.  If the compressor cycles fast, the system is low on refrigerant, the orfice tube is restricted, or there is a restriction in the high side between the compressor and the orfice tube.

This is all dependent on:
1. Clean condenser fins
2. Clean radiator fins
3. No debris between the condenser and radiator
4. Good air flow through the condenser and radiator
5. The CORRECT charge of refrigerant

This controls the ability of the condenser to remove heat from the condenser.  The condenser changes high temperature, high pressure gas into a high pressure, high temperature liquid which at the orfice tube, because of the small orfice and pressure drop caused by the restriction, the refrigerant is transfer into a low pressure, low temperature gas.

The higher the high side pressures the less cooling you will have.

Sealing the hood to the radiator support and the radiator to the support so all the air when driving or idling has to go through the condenser and radiator will greatly increase performance of the system.

Also, the engine can not be overheating.

Hope this helps explain how your clutch cycling system works.

["Cadillac Kid" Greg Surfas 15364]

Paul,
One thing I forgot to mention is how would you find a leak if you were relying upon vacuum holding as the test for leaks?
VIR's were incorporated in late model 73's.
At higher ambient temperatures, the condensing temperature and pressure is higher. Since the evaporator is the device that removes the heat from the cabin, and it has a fixed maximum capacity, the fixed flow orifice is what controls the refrigerant flow to it.  At higher ambient temperatures and pressures, the fixed device has to restrict the flow to the evaporator more than it would at lower pressure, so it allows less, not more refrigerant to flow, hence the "problems" at lower outdoor temperatures.
Greg Surfas

[Chopper1942]

Holding a vacuum is not a good indicator that the system is OK and does not have a leak. If your system was very low or empty, you have a leak.

The problem trying to find a system leak is a small leak will not show up easily.  Remember that the AC system does not operate under a vacuum. Pressures in the system can go as high as 440 psi before the pressure relief valve wil blow off.

The purpose of evacuating the system, creating a vacuum in the system, is to remove any moisture that enters the system while making repairs.  In your case, I would install a new desiccant bag after you find your leak and make repairs. Then I would evacuate the system for at least an hour. Depending on altitude, the low side gauge should read 30 inHg or very close.

Traces of oil on the hose/line fittings, and the compressor seal can be an indication of a small leak.

Because R-12 is so expensive, you don't want to use it to find your leak. 

The best way to find a leak is to use CO2.  Charge the system with CO@ to no more than 200 psi. The two ways now to find the leak is with soapy water, spraying it on all the hoses and components and look for bubbles, or use a CO2 detector to pin point the area and then use the soapy water.

To check the evaporator, you need a CO2 detector.  You must plug the evaporator drain hose and wait maybe an hour.  Then remove the plug and place the detector at the hose.  If it goes off, you have an evaporator that is leaking.

[bctexas]

I rebuilt an R-12 system in a non-Cadillac a couple years ago and tested using nitrogen at about 120 psi.  Bubble solution revealed a couple of fitting leaks.  Once repaired the system held nitrogen pressure for 24 hours without change, so I could vacuum and charge the system successfully. 

[Chopper1942]

N2 works to pressurize a system, but the problem is it is not detectable.  If the leak is in the evaporator, you won't find it.  Soap bubbles work OK on large leaks, but small leaks are more difficult to find.  I used to use soap and N2, but could not always find the leak. With the hige price of YF1234 and R-12, I now use CO2, a CO2 detector, and a spray foam that changes from pink to yellow in the presence of a CO2 leak to confirm the exact location of the leak. Automotive Test Solutions make the foam.

["Cadillac Kid" Greg Surfas 15364]

An electronic leak detector can instantly pin point leaks as small as a few ounces per year. They are not that expensive and even relative less expensive when you consider the current price of R-12 at $110.00 per pound. Of course the other common refrigerant R-134a costs less but with its phase out it will catch up to 12 before too long.
Greg Surfas