AC charge questions...

[DavidT]

I need to charge the AC system in my 91. The previous owner installed a rebuilt motor before I bought it, but never charged the system. The compressor/clutch seem to be fine.

1. Can I just add R12, or do I have to add oil too?
2. If so, what is the best way to add the oil? With the s/c setup, I really don't want to dissassemble things unless I HAVE to. Is there a way to add oil w/out removing everything?
2B. If I DON'T add oil, what could happen?
3. Can you mix the freeze 12 stuff with R12?
4. Which is the low pressure fitting and which is the high pressure fitting?
Thanks.

 

[Rob94]

1) Yes, but YOU cannot purchase R12. You need to be a licensed HVAC contractor, and it is extremely expensive.

2) Whatever oil is the proper for a R12 based system.

2b) Lack of lubrication. Compressor damage could result.

3) I have no idea, but I wouldn't try it.

4) The low pressure fitting is against the firewall.

AC work is more complicated than just adding refrigerant. You need to know what the system pressure is, both high and low, and you need to know how to interpret those pressure readings. With an R12 system, either don't mess with it, pay someone to do it, or convert it to R134a.

 

[SHO_Driver]

If you wanna be cheap, change the fittings to R134 low and high pressure fittings. Fill it up with R134 and drive. Did it on an Accord I was borrowing for a few months. System held up for 3 years and worked ok, not amazing. Had it vacuum tested first to make sure there wasn't a big leak and I knew everything else in the system was good. Definately not the best way to fix an a/c and supposedly not good in the long run.

 

[Ishodu]

If the system has been opened it will need to be evacuated. To get rid of all that air and to boil off any water vapor that could be in there. It may also as suggested time to convert over to 134a.

 

[DavidT]

this MIGHT sound lazy, but I REALLY don't want to remove the blower, etc... to get the ac working again.

To convert it to R134A, I WILL have to remove things, correct? OR, is it simply replacing the high and low pressure fittings that are staring RIGHT at me in the engine bay?

BTW, I DO already have two 12 oz. cans of R12.

How hard is it to evacuate a system?

 

[Ishodu]

this MIGHT sound lazy, but I REALLY don't want to remove the blower, etc... to get the ac working again.

To convert it to R134A, I WILL have to remove things, correct? OR, is it simply replacing the high and low pressure fittings that are staring RIGHT at me in the engine bay?

BTW, I DO already have two 12 oz. cans of R12.

How hard is it to evacuate a system?

To evacuate a system you wull need a vacume pump designed for the job. Its good that you have some R12 but I don't know how much you need along with oil. I am sure someone that knows more can speak up.

 

[TYSHO]

Walmart has a kit for the conversion. All you do is insert the new fittings over the R12 fittings, evacuate the system, and charge the system back up with the oil and R134a provided, which is compatible with R12 residue.

 

[DavidT]

so how do you add oil? Will things have to be removed?

 

[Ishodu]

so how do you add oil? Will things have to be removed?

As long as there are no leaks I don't think you have to remove anything. Not 100% sure though.
BTW nice Pic of the Gen3

 

[TYSHO]

The kit from walmart has three cans that are mixed with refrigerant and oil, so you just put it in through the low side fitting(blue).

From what I was told, you can put oil in the system the same way as refrigerant.

 

[DavidT]

As long as there are no leaks I don't think you have to remove anything. Not 100% sure though.
BTW nice Pic of the Gen3

thanks

Soooooo, to convert to R134A, you just have to change over TWO fittings?

 

[sdpatt]

If the original R12 system does not have any severe leaks, take it to a certified shop and have them recharge the system correctly with R12 and any oil that they will add if needed. R12 is the best, most efficient refrigerant for automotive systems and the R134a conversion will not have the same cooling capacity.

To convert from R12 to R134a is not as simple as some of the previous responses would make it seem. You can evacuate the R12 and add R134a and its oil, but the system will not last long. The oils are not compatible and the dryer must be replaced to remove the oil it hads absorbed. The system must also be properly flushed of the old oil. The Ford seals will need to be replaced since the R134a is a shorter molecule than the R12 and can escape through the old seals.

Use Google or any other search engine to search the web for the connversion process. Learn for yourself what the correct method is to perform the conversion from R12 to R134a. On a trip my SHO had the liquid line cut by road debris and the system lost all of the R12. I was 500 miles from home and the Ford dealership that I took the car to suggested that the conversion would cost only marginally more than the R12 recharge. I have been pleased with the conversion, but I am aware that the A/C system just does not cool as well on those really hot days as the old R12 used to. Keep the R12 if you can.

 

[DavidT]

please don't me.
gosh, here is what I WANT to do:

simply add the TWO 12 oz. cans of R12.
Will this ALONE be detrimental?
Now back to the oil issue... can IT be added the same way as the refrigerant? And is it a MUST?
Is evacuation a MUST?

 

[freeze]

yes you can, it depends how much the system has leaked. look for oil around the fittings if there is not any you will not have to put in any oil. imo I would sell the r-12 and convert it to r-134. r-134 will get cold my vent temps are around 40 degrees. the oil goes in the same way. If you decide to go the retrofit kit give me a call and i'll tell you how to do it (918) 381-3540

 

[Rob94]

Whatever you decide to do David, keep in mind that you CANNOT purchase R12. It has been banned worldwide, and is not available for sale to consumers. If you want to keep the system as an R12-based AC, you will have to bring it to a shop. Either route you take, it will be rather expensive.

 

[AutoSHO]

please don't me.
gosh, here is what I WANT to do:

simply add the TWO 12 oz. cans of R12.
Will this ALONE be detrimental?
Now back to the oil issue... can IT be added the same way as the refrigerant? And is it a MUST?
Is evacuation a MUST?

Quite simply, yes, it will probably be detrimental. Being as you don't know what charge the system currently has, how much oil is in the system, or a vacuum pump to evacuate the system (which is, yes, necessary) - You will probably do more harm than good (along with wasting 2 cans of rather valuable R-12). Also, the car's A/C system holds more than 24 oz. of R-12, so even if the system is completely empty of R-12, you will not get a full charge from those two cans.

Also, if the system was opened when he did the motor swap (not sure why he would, you can leave the compressor in the car and never break anything open) then you absolutely need to have it evacuated, oil added, and then the proper amount of refrigerant added. Chances are if he broke the lines open, he drained out quite a bit of refrigerant oil.

I also agree with Scott, R12 is colder than R134a - I have ridden in many SHO's (including my own) with R-12 and it does get colder, faster, than R134a. This is mainly due to the fact that R134a does not have the heat transfer capacity that R12 does. It has considerably less, as a matter of fact. In my R12 equipped car, on an 80 degree day, I have seen air temps as low as 36 degrees, measured in the center vents on the dash. My friend's 90, which has been converted, does not get that cold, BUT - he can recharge it whenever he feels like, not worry about leaks, and R134a costs $1.50 a can. The choice is yours - but I highly recommend taking it to an A/C shop if nothing else to get it evacuated and leak-tested.

 

[rangerj]

David T,

If, and that is a big IF, the prior owner changed engines WITHOUT discharging the A/C system then you can add oil without opening up the system. You can also add refrigerant, say the two cans of R-12 you possess.

However, understand that an A/C system is a sealed system, and if it needs a refrigerant charge then it has a leak, period.

So, how long will your R-12 refrigerant charge last, given the system leak? The oil in an A/C system flows through the system with the refrigerant so that if there is a leak you have also lost some oil. You should be able to get a tool from Auto Zone that injects oil into the system through the schrader valve on top of the low pressure switch. As I recall it is a rather inexpensive tool as it is not intended for professional use.


So here is what you can try.
Check to see if there is any pressure in the system at all. Do the by depressing the low pressure schrader valve for an instant. If you get a release of pressure then there is some charge in the system. If the system is dead empty, then it has to be evacuated (vacuumed) for at least 45 minutes to an hour. If this is the case you may as well fix the leak(s)

Get the oil injection tool with a fitting for R-12 (R-134a uses a different size of fittings). Inject about 2 ounces of R-12, or R-12 compatable oil (synthetic). Then add your two cans of R-12. If they are 12 ounce cans you will have 24 of the 36 ounces of refrigerant required. The system will work well enough to see if it would be worthwhile to have a shop add the other 12 ounces. Then see how long the system holds up. It could last a day (or less), or it could last a year or two.

As for your "Freeze 12" question, if you add any of this stuff you will not be able to get any A/C shop to touch your system. If you do not tell them you used it and they pump it into their good R-12, and ruin their refrigerant, they will charge you for their loss, as the mix has made their product unusable. A 30 pound tank of R-12 at $135 per pound will cost a bunch of $$$. Stay away from that CRAP. rangerj

 

[Xs SHO 1]

Whatever you decide to do David, keep in mind that you CANNOT purchase R12. It has been banned worldwide, and is not available for sale to consumers. If you want to keep the system as an R12-based AC, you will have to bring it to a shop. Either route you take, it will be rather expensive.

I don't know about banning it worldwide, it is close to no longer available in the U.S. in general. But the third world countries are probably still using R12....

 

[Xs SHO 1]

Converting from R12 to R134a is not as easy as people make it to be. Both refrigerants and oils are not compatible, so you need to basically completely evacuate the R12 and oil properly, replace the o-rings and oils, pull vacuum to see if it holds or if you have any leaks, then charge the system. if it does not hold vacuum, then you have a leak somewhere, that too needs to be fixed.

As far as the kit that people tend to buy, my opinion is, you get what you pay for. The unnoticed reason for this is, if you properly evacuate and charge an a/c system, equipment alone will cost you in the $1k area. That would include your evacuation system, manifold guage, color coded evacuation tank resevoir, that's basically it with other misc. The only place that can afford to have all this is either a certified shop or a qualified HVAC personel. It is expensive, with a small price to pay for a cleaner environment.

One more note, one way you can tell if your car has the R134a is, the low side line will have the blue cap and the high side line will have the red cap....

 

[DavidT]

I depressed the high and low schrader valves... BOTH had SOME (little) pressure.
Do I STILL HAVE to evacuate the system before I add the R12?
When adding oil, do you do it BEFORE or AFTER adding R12?