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Does 1976 with VIR have an adjustment

BG1 on Tue June 29, 2010 9:54 AM User is offline

Year: 1976
Make: Pontiac
Model: Firebird
Engine Size: 455
Refrigerant Type: r134a
Country of Origin: United States

I need to change a ac hose on my car and the system will turn on but does not get cold but this is because of low freon. It has r134a in it and I need to change the hose and replace the freon. I did put a set of manifold gauges on it and the freon/oil that came out of the connection looked like brownish whipped cream kinda, I do not know if this means it has moisture in the system or if it is supposed to look like this. I have heard that the vir has a poa inside that needs an adjustment for the r134a and I have heard the opposite. I have also heard that when converting a car that has r12 to r134a that the old desiccant designed for the r12 system will not work with the r134a. I would like to get the system cooling again so if someone has some information that will help that would be great. Thanks

Chick on Tue June 29, 2010 1:33 PM User is offlineView users profile

check out VIR kit with desiccant.. The oil you describe does not sound good, especially the foaming..could be sealer or other junk, I would flush the system while you have it apart and add fresh BVA Auto 100 ester oil if using R134a.. The guys at can help you with parts and supplies.. Just e-mail or give them a call..

Email: Chick


Freedoms just another word for nothing left to lose

ice-n-tropics on Tue June 29, 2010 5:45 PM User is offline

When I serviced my 1974 Camero with VIR and A-6 compressor and other A-6 equipped vehicles, it was common to see brownish or rusty oil with refrigerant out gassing from the oil to create brownish foam. Those old GM hoses allowed lots of moisture to migrate inside the A/C system and some light rust and acid was the result. With the new desiccant and filter in the VIR there was fantastic cooling in the 1974 Camero for 50,000 more miles. New desiccant holds about 15% acid and cleans up the system as refrigerant circulates across the desiccant.
With R-12 and the proper amount of genuine Delco mineral oil, that's one of the best A/C systems ever made.
Can't recommend R-134a and changing the VIR superheat setting.

Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy. How To Air Condition Your Hot Rod

fonebone on Sun July 04, 2010 11:47 PM User is offline

Hi BG1- Sorry to hear you converted over your VIR A/C to 134. There is no adjustment on the POA valve, although a while back someone did have a way(do a search here under VIR POA). You will never get cold temps with 134 with a VIR unit. I'm still running a 79 Caprice to work. I converted it to a VIR unit almost 20 years ago, from a CCOT system to a used 74 Monte Carlo unit that blows 45 degrees out the vents, so these can cool nicely with r-12. Factory calls for 48 to 52 degrees, so that made quite an improvement. At the suggestion of the group, the last time I opened the system and changed the drier bag, I also installed an aluminum parallel-flow condenser that is much better than the factory unit. Back to your car- As per factory instructions- once you open the system, remove your compressor. You will notice a drain plug at the bottom. Drain into a measured container. If under 6 ounces, refill with 8 ounces. If over 6 ounces, refill with that same amount. Replace your rear o-rings, coat with NYLOG, when re-installing the compressor to avoid leaks. ( both available here at this site). Also. the newer desiccant bags in the VIR kit work with r-12 and 134. With the VIR kit, make sure the contact area of the inner, round o-ring(there are 2 o-rings, a square outer one, a round inner one) that is in the "can" that is held on by screws, is not etched from corrosion. If so, carefully smooth it out with scotch-brite and fine grit sandpaper and get it as perfect as possible. Years of use will etch it. The can comes off REAL hard. Gently pry around the lip till it comes loose, have patience. Install 1 ounce of oil into the can with the new bag before re-installing. Buy some NYLOG, available here, for r-12, coat the o-rings completely to assure a leak proof seal. This is mandatory! Hope this helps you.

BG1 on Mon July 05, 2010 7:25 AM User is offline

Does this system use an orifice? I do not see where its located if it does and I see that auto parts stores list them for this car. Thanks

fonebone on Mon July 05, 2010 7:04 PM User is offline

Hi- No, your car does not have an orifice tube; that's for the cheaper cycling clutch orifice tube-CCOT, like my Chevy had from the factory. Yours(and my conversion) is a VIR, valves-in-receiver-unit, meaning that a couple of valves in the body of the VIR unit monitor pressures and adjust them to maintain a constant flow at controlled pressures for max cooling no matter what rpm you operate at. Went to GM school for this back in the 70's and really got to like it. The POA valve is set for r-12, not 134, which runs at a different pressure in the evaporator, and that means different vent temps(higher temps) when you have r-134 in a setup designed for r-12.

Edited: Tue July 06, 2010 at 12:31 AM by fonebone

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