R-12 air conditioning/recharge or convert?

[George C.]

Re: R-12 air conditioning/recharge or convert?

I converted my 71 over and it worked ok...for about two months, wished I would have just left it alone.

Stay with R 12. Save the Wave.>George

[William C.]

Re: R-12 air conditioning/recharge or convert?

If you speak nicely with a body shop owner, many have the equipment to work with R-12, but don't advertise the fact.

[Jim T.]

Re: R-12 air conditioning/recharge or convert?

Jim

Intriguing thread here. I recall we had a similiar about a year ago but tell us how you acquired the gauges, what it might cost us and if there is much "technical expertise" required to do this ourselves. I've got two 78's both that need work and I've dragged my feet really not wanting to do a conversion. I've convinced after this...no need to.

Tom the guages I bought are Model #MF-3X Professional Air Conditioning Manifold Guage Set only useable for R-12 and R-22 so I can recharge my home units if I had to. I am trying to remember who I bought the gauges from.
Only used the guages twice since I have owned them. They come with instructions. I have not connected the high pressure guage either time. Went by the instructions in my 85's service manual using only the low pressure guage connection and the 87 Honda Accord many years ago had a sight glass that makes it so easy to charge. I am going to hook up my 70 in a few days and charge it.
I may have bought the guages from J C Whitney.

http://www.id-usa.com/product.asp?CID=43&PID=193

[Christopher R.]

Re: R-12 air conditioning/recharge or convert?

Harbor Freight has A/C gauges for around $40-$50. There's 20% off coupons in this month's "Car and Driver" and "Road and Track."

Google "auto air conditioning bulletin board." There's some good ones.

A/C isn't any more difficult than other auto repair stuff. The only specialized tools are the gauges and a vacuum pump. Vacuum pumps can be pricey. But used ones are always on EBay.

[Tom L.]

Re: R-12 air conditioning/recharge or convert?

Thank you for adressing the "pressure/temperatre" relationship. It is the single most important principle in A/C and refrigeration theory. The feel test is just that, a feel. It DOES NOT identify what is really going on in the system.

As far as guages go, ANY guage will work with ANY refrigerant as long as the pressure/temperture relationship is understood. If anyone thinks that the guages are different I'll point out the difference:

The guage indicate Pounds per suare inch only. The manufacturers have for 30-40 years placed the pressure vs. operating temperature of differnent refrigerants on the face to aid technitians in service work. Back in the day they were R-12, R-22, and R-502. After the Montreal Protocol (the agreement that led to the phase-out of CFC's) alternative refrigerants were developed. Since then tool companies have marketed guages for "specific" refrigerants.

If you have a set of guages and understand the Pressure /temperature relationship of refrigerants, go to sporlan.com, dowload a pressure/temperature chart and you will have every set of guages on the market in your hand. Excluding R-410a (this refrigerant will be better known soon. R-22, the refrigerant typically used fro home A/C is currently being phased out) and a few exotic low temp refrigerants, but those do not apply to auto A/C

[James W.]

Re: R-12 air conditioning/recharge or convert?

This is great information everyone.

Now I have a question. I have a 1965 Corvette with factory a/c that was converted to R134 several year ago. I recently had to replace the expansion valve and was fortunate enough to find an NOS Frigidaire unit. All other componets are original except the dryer. I have not recharged the system yet since replacing the expansion valve.

My question is can the system be converted back to R12 coolant?

If so what must I do to convert it back?

I am planning on buying a new dryer and have found and purchased a bottle for the GM 300 viscosity compressor/cooling system mineral oil.

Any help would be greatly appreciated.


Thanks,

James West

[Kenny C.]

Re: R-12 air conditioning/recharge or convert?

[Duke W.]

Re: R-12 air conditioning/recharge or convert?

One of the biggest conversion issues is the oil. R-12 uses a mineral-based oil and R-134a uses a PAO synthetic. They are incompatible.

Since liquids cannot exist in a vacuum, one way to purge most of the old oil is to draw a vacuum for a LONG time - like 24 hours, which is what Mercedes Benz recommends.

I have also heard that there are ways to flush the old oil out of the system, but I don't know the details.

In any event, you need professional A/C service equipment to do the job, so if you don't have such, you need to find a shop that can do the job, and you should understand how they intend to do it.

One of the advantages of using a professional shop is their ability to find leaks. Many insert a die that can be seen with a UV light, some use ion detectors, and some use both. There are differing opinions on which work best, but a good tech should be able to find any leaks regardless of the method used.

Anyone can look for leaks by looking for a film of oil, which is almost always a tell tale sign since the refrigerant carries the oil in suspension. On a recent service of my MR2 I found an oil film on the evaporator drain hose, which made the expansion valve suspect. Toyota had a service campaign on it back in the late nineties, and they would have replaced it at no charge, but since it wasn't leaking I demurred because I didn't want them to "tear the car apart" to get the evap housing out. Big mistake!

It turns out that removing the evap housing is easy (kudos to Toyota for designing "serviceability" into the system.)

In addition to the expansion valve, the tech found a leak at the condenser output coupling, which I had failed to find.

The total bill was about $300, including two pounds of R-12, which I considered quite reasonable.

Duke

[Jim T.]

Re: R-12 air conditioning/recharge or convert?

This is great information everyone.

Now I have a question. I have a 1965 Corvette with factory a/c that was converted to R134 several year ago. I recently had to replace the expansion valve and was fortunate enough to find an NOS Frigidaire unit. All other componets are original except the dryer. I have not recharged the system yet since replacing the expansion valve.

My question is can the system be converted back to R12 coolant?

If so what must I do to convert it back?

I am planning on buying a new dryer and have found and purchased a bottle for the GM 300 viscosity compressor/cooling system mineral oil.

Any help would be greatly appreciated.


Thanks,

James West

Interdynamics has R12 air conditioning compressor oil that is listed as viscosity 500 S.S. U. @100 degrees. Do not know enough about the differences on 300 and 500 viscosity compressor oils and what the true actual requirement is required for a Corvette's system

My 85 service manual gives the information to open the doors, blower on high, air conditioning on, and gives rpm of 2000 for adding R12.

A fully functional original R12 system will cool better than R134 from all that I have read about it. The cost of R12 and draining the compresser of oil may make your decision to convert back to R12.

[Phil D.]

Re: R-12 air conditioning/recharge or convert?

As far as guages go, ANY guage will work with ANY refrigerant as long as the pressure/temperture relationship is understood. If anyone thinks that the guages are different I'll point out the difference:

Most guages sold to ordinary backyard mechanics come packaged with a set of hoses outfitted with standard connectors for that type system - i.e. r-12 gauges have those old screw-on fittings and r-134 has snap-on fittings. But yes, pressure is pressure regardless what type of gas you're measuring. I bought a set of r-12 gauges a few years ago along with a set of adapters for r-134 fittings so that I can do both with one set of gauges.

It turns out that removing the evap housing is easy (kudos to Toyota for designing "serviceability" into the system.)

Duke

Off topic, but I too have been spoiled working on Toyotas. I only need my 2lb brass hammer for american cars.

[Jim T.]

Re: R-12 air conditioning/recharge or convert?

This is great information everyone.

Now I have a question. I have a 1965 Corvette with factory a/c that was converted to R134 several year ago. I recently had to replace the expansion valve and was fortunate enough to find an NOS Frigidaire unit. All other componets are original except the dryer. I have not recharged the system yet since replacing the expansion valve.

My question is can the system be converted back to R12 coolant?

If so what must I do to convert it back?

I am planning on buying a new dryer and have found and purchased a bottle for the GM 300 viscosity compressor/cooling system mineral oil.

Any help would be greatly appreciated.


Thanks,

James West

My 64 Corvette Shop Manual Supplement ST34 air conditioning section for system capacities has:
R12 freon charge 3 lbs. 4 oz.
Oil charge 11 oz. of 525 viscosity oil

James West did your new expansion valve have the metal filter screen for the inlet? Did you check your old expansion valve's filter screen for contamination?

[Gary N.]

Re: R-12 air conditioning/recharge or convert?

The original A-6 compressor on my 66' says to put in 2.5 lbs. of R-12 freon. I have recharged the system myself and it is fairly easy to do. As others have said be sure to pull a good long vacuum to boil off any moisture. I usually shut off and close off the system and watch to vacuum and make sure it will hold a constant vacuum. Make sure you know the high side from the low side to connect your gauges. Make sure that you purge the lines with freon as you connect up your freon source to the low side. If you use the small cans you might have a bucket of hot water and put the can down it as it starts to ice up. It will help change the liquid freon to a gas as it goes into the system. If you use the small cans you know how much each can holds and can get an idea of the amount you have put in. If you use a 30 lb. container you would need a good scale to weigh the amount of freon used. I usually watch the sight glass as a gauge as to how close it's getting also.