So i have remove my A/C last year on my 1979 but i would make it work again! but in this i'm a neewbie
so i need advice !
how to check my compressor?
what part i need to chage?
witch refigerant?
oil!?

thanks!

 

Oh man....have you got a long hard road ahead of you....good luck!!

 

Well I asume since you took it apart you have the parts and can get it put back together. I don't know how you would go about testing the compressor, but what I would do, is go ahead and put it all back together after flushing the parts, Use R134A compatibla parts. Then put in a test gas and fire it up and see what it does. If it comes up, your good, if not you could get a direct replacement, but I would go with the sanden 508.

 

You're gonna' need a dryer. The aluminum looking thing on the firewall that looks like 2 beer cans. An expansion tube. A really good flush of the condenser and evaporator and lines. Water (moisture in the air) gets into the aluminum condenser and eats it from the inside out like acid. Same with the evaporator. Unless you sealed everything up with correct caps and plugs, you'll be replacing them in the future. And the Sanden compressor is much more efficent than GM's are.

 

a new drier like tim said, and you'll need to change the o-rings to the r134 compatible ones. fill it up with test gas (argon i think) to check for leaks

 

Is it true that Sanden compressor are indeed more efficient?

 

jerome1979,

I am assuming that you still have all the pieces for your system but that they've been exposed to the atmosphere all this time. What has been said about the accumulator/dryer is true--you will need a new one if it hasn't been capped off since the dessicant in there will have absorbed moisture from the atmosphere and will be basically worthless.

The tough part about this whole thing is that it is an R12 system. It is very hard to find R12 these days and if you can find it, it's expensive. Just search ebay and you'll see. I'm assuming you're not sure if your compressor even works. There's no way to test it until you have refrigerant in the system. If it were mine, I would convert to an R134a setup. You might find that vintage air or one of the aftermarket vendors like that has a system that you can replace everything with. I know this is a bummer b/c of cost. You cannot fully purge your old system of the old oil that's in the compressor, condensor, evaporator and hoses enough to put new oil in and not have a compressor failure. Ester oil (R12 systems) and PAG oil (R134a systems) are not compatible. Also, your old hoses will not be effective in containing the R134a refrigerant since the molecules are smaller from R12 to R134a.

I'm not trying to be negative here, just trying to help you out. If you have anymore questions, don't hesistate to ask.

 

I don't have any hard facts other than they weight about 1/3 what the old A6 does.

 

Ester oil, polyester oil, and pag oil is for 134a.
Mineral oil is for r12.
When converting r12 to 134a the sytem can be cleaned of old oil by disassembly and proper flushing with no detriment to the compressor.
R12 is available but pricey. The problem is that not all shops are setup to handle it these days and it would be foolish to risk a minimum $25,000.00 fine to help a stranger save $200.00.

The Sanden and A6 performance comparison is self explanitary as per the chart. The A6 will provide a cooler climate in a comparable system.
The Sanden is smaller, lighter and has a smaller displacement which will translate into slightly better economy.



BTW the Sanden 508 is an almost obsolete model number. The demand is very low with extended lead times like the BFGoodrich 245/60/15 tires and look for production to cease altogether.
The 510 is not available as far as I know.
The replacements are SD5H14.
So, if you have a good A6, I wouldn't jump thru hoops to change to a Sanden.

Moisture in the system is what causes the acid, and the necessity to replace the accum/drier whenever the system is opened.

All replacement parts unless old OEM, I have seen are compatable with both r12 and 134a.

The cheapest way to test for leaks is nitrogen and UV dye.
The only way to test compressors and older expansion valves etc is to charge and test pressures and temps

 

Noonie - that's an interesting document - I found it on the web at Air Conditioning Performance Facts & Comparisons of Various Mfg Units while trying to find out what a DKS 26 Diesel Kiki was.

The article notes that "Each air conditioning system should be balanced between the compressor, condenser and the evaporator to achieve the performance desired on each application. The capability of the compressor will determine the performance and not the size and
BTU rating of the evaporator and condenser listed. This is especially important when choosing an air conditioning system for truck, buses
and larger vehicles." BUt - they forgot to add 'corvettes'

I hear what they are saying, but I do not the technical background to follow thourgh. Obviously the component seelction is very important. I know we always talk about R-12, R-134a, or..... but once you determine to go say R-134a (and I am), then I assume the condensor comes as a large issue. Can you input on this and do you have any comparisons/data on various types/brands? What about the evaporator suited for R-134a.

Last - does anyone have a pic of a C-3 with the system (Vintage Air or Hot Rod) that elimaintes the evaporator box and has a clean firewall installation?

 

kaiserbud

I've got a lot of a/c charts that are not complete docs. Don't know where they originated. Your article is from a retailer, but I suspect it came from dist at one time.

Balancing a system is very important, but in reality we are using a very small cabin size and the availability and space considerations severely limit choices.
In reality all that can be done is to increase the efficiency of the system as it is sized for the cabin.
This basically involves reclaiming the difference between r12 and 134a. Changing the condenser can do this.
-change to the largest parallel flow condenser you can fit in.
-add an additional condenser fan for a/c alone
-keeping the original compressor size (10.6cu in displacement)
the original "plate type" evaporator is as good as it gets and are available new for a little over $100.00 and not $300.00 plus from specialty venders.

If you have the original a/c box and controls keep it, clean it, and repair all leaks, change to a vov oriface tube, PL condenser, condenser fan, and compressor of choice and you should get vent temps of 36° at ambient 90° sunshine.

Although I haven't used it yet for a C3 a MarkVII type fan with a DSS controller with the a/c function added to the a/c switch seems to be the best alternative. You should always have air flow over the condenser if the a/c is on regardless of engine coolant requirements.

As far as the aftermarket systems, they can be unecessarily pricey, if you already have most of the oem components.

 

Does a 79 still use the A6 style compressor? I thought that the R4 (? the flattter bigger diameter) compressor was used then.

Noonie: How would these two compressors (the A6 and R4, not really sure about the designation) compare? The later style one must have been used on a hundred million cars!

 

Checking a compressor- If it turns using the center front nut nicely & compresses air it is probably good. The second part is to check for leaks- usually done by placing a vacuum on the system & waiting to see if it will hold for several hours. A compressor leak is normally the front shaft seal. It can also be tested for leaks by pressure- the normal system pressure is about 100 psi w/ system off.

At this point newbies should probably get the assistance of an A/C man who will have the equipment to evacuate & properly charge. Operating pressure exceeds 200 psi on the high side- a mistake of trying to charge the high side could be very dangerous. Not for newbies.




Compressors
Most A6s are 12.6 c.i. except for Corvette & Corvair which used 10.8 c.i. models. R4 is about 10 c.i. & was also used in El Dorados, etc.

I replaced the R4 with a ND 6P (8.2 C.I. & similiar to Sanden 508) which uses less HP & works great. Compressor, custom brackets & hoses to stock A/C system w/ R12. Note how the A/C lines go off to the side & then straight forward & back.
http://ganeys.home.sprynet.com/77ACs.JPG

 

So - the important 'balance' can be obtained with OEM components?
For me, I am at a major fork in the road as I need all components. Do you know what is the biggest/best largest parallel flow condenser? When I checked with Hi-Lo AUto Parts today, they said it was just a regular condensor Looks like I will have to do some research on a "plate type" evaporator too.

I heard there were different types of VOV - how do you know which to use? Since I did not know what a VOV was - I found this on the vov orifice tube http://www.aircondition.com/vov/......

The Smart VOV (variable orifice valve) uses system pressure and refrigerant flow to move a metering piston relative to a fixed opening in the sleeve. The piston movement is resisted by an attached spring.

When idling at high ambient temperatures, the piston shifts to a smaller metering area similar to a TXV. This compensates for the reduced compressor output and increases the cooling performance. The Smart VOV also has a unique re-open feature which reduces compressor pressure for severe idle conditions.

At highway speeds, the Smart VOV operates on a large orifice. The net result is better performance than a TXV without the complexity or reliability concerns.

Unlike a TXV, which has constantly moving parts and small internal clearances, the Smart VOV is stationary during most operating conditions and has large internal clearances. Its low friction floating design insures smooth operation and extremely long life.

 

Here is the difference in design:

C3's came with the tube an d fin type. PF's are used in late model Caravans and most Mercedes, to name 2, if you want to eyeball one. Your parts store doen't know.

C3's came with a plate type evap, can't improve on it.

There is only 1 vov manufacturer that I know of, and it's the most sensible solution for a 134a conversion.

Here is a couple of examples.

http://www.ackits.com/merchant.mvc?S...t78corvette5-7

http://www.aapak.com/Qstore/p000116.htm

As I said before I would use an axial piston type compressor with an oil resevoir such as an A6 or Sanden.

 

Sorry to ask this again but I can't be the only one who does not understand the designations for C3 compressors (A6 etc.). From an uneducated eye (mine), it seems that two styles of compressors were used on C3's. The longer, smaller diameter "early" style and the "later" shorter larger diameter style. Which one are you guys talking about and what is the designation for each? The original poster seems to have a 1979. Does it come with this style compressor?

 

BBShark
That' a radial 4 piston compressor used on Corvetted from 77 on up.
It was used a lot and underwent a lot of improvements, but the earlier A6 design is much better and has been copied by a lot of companies like the popular Sanden.

 

This is the style compressor that is in my 79 and that has been upgraded with R-134A. It blows plenty cold, but the fan only works when the switch is on the high setting. Can I assume it is a bad switch, or could a relay or something else be the problem?

 

Check the resistor pack on the evaporator case on engine side firewall to see if you have voltage in/out.

 

Hi Noonie - can you clarify whether you meant to say C3 in both statements above? If so - can you explain?

Excuse the lack of knowledge.... but you must be suggesting to change to possibly a Caravan or Mercedes evaporator. So - if we did - do these 2 specific ones fit well - or are we only looking for just any evaporator to 'fit' into the casing? and if so - are there any guidelines/warnings?

I have my A/C /heater box of off the car, but have to go look at it and see what is 'in there'. I will tear down this afternoon.