1979 Seville Air Condtioning

[d j deluco]

   I own a 1979 Seville and want to change over from R12 to 134A. What is needed and what is the process? Any help would be appreciated. Thank Youl

[Dave Shepherd]

Lots of anecdotal info out there on this process, I have had " some" successs with the cheap conversion kits out there, but in an old car I could almost guarantee 134 will find leaks.  I would google this conversion and pickout what seems like the most relaible info.  But first you must determine the condition of the system, condition of compressor, hoses and connections,  the ac should be drawn down to test for leaks first.

[TMoore - NTCLC]

Yes, find out what is going on first.

Is your system still functional, but not cold, or has the system been inoperable for a while now?  If you are just due for a charge, and are thinking that 134 would be simpler, I encourage you to reconsider.  R12 is what these systems are designed for, and a properly functioning system with R12 will be far superior to 134A.  You can still find R12 - the price might be a bit steep, but if you just need a pound or so to top off your system, you will be miles ahead to keep it R12.

[TJ Hopland]

If its been working and just recently got weak I would just get it recharged with R12.  Most good shops still have it and it was not terribly expensive last time I looked.  Its just less hassle and works better in the old systems. 

If it has not been working for a while like a year or even years then its likely going to need some work.  Once the systems leak down they tend to start sucking in air and moisture especially if they are in a climate that has extreme seasonal swings.  The moisture is hard on things like the compressor.   The 'right' way to do a system that has not worked for a while or a conversion is to replaced the compressor, receiver dryer, orifice tube, o-rings, and flush the rest.   You in theory replace the compressor on a conversion because you cant get all the old oil out and the old and new oil dont mix well.  You in theory replace the compressor on one that has not been working just so you know you are not going to have problems.  So you may have noticed that all those parts required for the 'right' way is everything but the hoses, evaporator, and condenser.  You could just recover whats R-12 may be left in the system, vac it down, charge it with 134 and ester oil and see what happens.  Worst case it trashes the compressor and you are back to the 'right' way of doing it which included a compressor anyway.  Best case it works for a couple years.   Lots of systems were done that way with success.  The ester oil seems to be a universal oil that works with pretty much all the compressors and refrigerants.  It also tolerates mixing with other oils.   I found out its what many shops use if they dont know what is in the system.

Does the 79 Seville still use the long A6 compressor?  Or the flatter R4?  That was around the time they switched.  Either way they are both pretty easy to come by.  The R4 is a little more common because it was used till 95 but the A6 was used for many years so the 'classic' vendors would have them for sure if the regular parts stores dont. 

134 on this vintage system cools just fine cruising down the road where its lacking is at idle and slow moving traffic on a hot day.  It will blow cooler than ambient temp but it usually wont be cold.  After the first year or two of 134 in the mid 90's most manufactures went to a variable displacement compressor to help that issue.   

[Gene Beaird]

The 79 Seville uses the A6 compressor.  The A/C on our 79 was converted, and it works wonderfully.  It was that way when we bought the car, so I'm not exactly certain what was done.  The whole under hood area is clean, but the A/C lines do look newish, or at least in very good shape. 

[TJ Hopland]

GM systems that used the A6 seemed to be pretty overbuilt and could freeze you out of the car when using R12 so converting them to 134 still usually gives decent performance.   The later R4 ones did not seem to be as over built presumably due to cost and weight cutting.  When you convert those it really depends on the climate and other conditions how well they work especially at low speeds.   Some of the other brands out there really had serious performance issues when converted. 

[planetcadillac]

I have converted ALOT of R12 systems over the years. It is much easier to make a CCOT (77+) work well than VIR or TSV systems. Several companies make CCOT retrofit kits for the older cars to make them emulate CCOT.

The biggest issue is to make sure you get everything CLEAN. Make sure that there are no clogs or obstructions in the system. Evaporators have a tendency to clog and degrade over time because of the tiny passages inside.

Get as much oil as you can out but a small amount of residual oil is not as troublesome because as has been said Ester Oil is the preferred oil for conversions and works well with residual mineral oil and R12 and R134a.

Replace ALL of the o rings with green VITON ones that are more resistant to degredation and are not as porous as natural rubber.

Replace any defective or damaged parts but if the part is clean and functional it can be reused. I have converted vehicles many times without replacing anything but the filter, soft parts, and oil/gas.

Proper cleaning and replacement of the soft parts will aid tremendously the efficiency of the system.

CCOT system (especially those from the 1980s) will use a pressure switch on the low side, and sometimes on the high side on newer cars. These switches are relatively inexpensive and should be replaced upon conversion. The system will run without new switches but because of differences in pressures between R12 and R134a, the trigger points will be "off" much like changing tire sizes on a car and the speedometer will be "off."

The last suggestion would be to use a variable orifice valve as opposed to a fixed valve. Here is a link with explanation: http://www.acsource.com/smartvov-highperformanceorificetubes.aspx

I do not have any link to that website I simply used it because it is laid out conveniently.

For those that are not mechanically savvy and do not do much work themselves on their cars, and who may not use the vehicles on a daily basis (which I assume is the case with most older Cadillacs) I have tended to recommend retrofitting to R134a. R12 is slightly cooler than R134a overall, but often is the case ease and cost of future service are a primary concern.

["Cadillac Kid" Greg Surfas 15364]

With R-134a being phased out (eliminated from all new cars produced after 1-1-2012) in the EU and Cadillac now switching to the EU approved HFO-1234yf, It won't be long before R-134ais at least as expensive as the $50.00 per pound R-12 costs (in the US).
In regards to "Make sure that there are no clogs or obstructions in the system. Evaporators have a tendency to clog and degrade over time because of the tiny passages inside", the only obstructions you will find on the refrigeration side of a system are those introduced as dirt while the system is open, or ANY residual Mineral oil combining with R-134a.
By the way, the estimated wholesale cost of HFO-1234yf is somewhere around $70.00 per pound, and will only be available in 30 pound drums ($2100.00).  While we are at it, you will need in the order of $7,000.00 worth of equipment (per the SAE Journal) to service the new systems.
The systems were designed to utilize R-12, and again if you are in the US, it still is avaliable.
Greg Surfas

[TJ Hopland]

The CCOT (cycling clutch orifice  tube or (FFOT ford fixed orifice tube for the ford folks)) change was not till 77?  Thought they did it in 73?

I have heard mixed thing about the variable tubes.  I was going to try one last time I had to swap a compressor but my local store didnt have the right one in stock so I went with a standard one.  Whats the theory on how they work?  And whats the theoretical bad thing about them other than the cost a lot more than the fixed ones?