I have a 1986 cadillac coupe deville. The system currently has r12 refrigerant in it and I want to convert it to r134a. Once I evacuate the system, do I have to put ester oil back in the system or can I simply replace the old refrigerant with the R134a?

This car uses R12, it is no longer available, you must convert it to R134, this requires the compressor and reciever dryer be replaced and the system flushed out and the new PAG R134 refrigerant oil be added and new charging port kits installed. Is that car worth this effort?

F48= "Very Low A/C Refrigerant Pressure Condition" In short your AC has a leak and is low on charge. This is an R12 type refrigerant system most likely so if you haven't converted it to R134 you may have to do that.

This car originally contained R12, if you can find it you can use it. The other option if this has not already happened is you can convert the system from R12 to R134a, which is readily available, all auto part stores carry these kits. R12 AC fitting are threaded and R134a systems have slip on quick connect fittings.

Your have a low refrigerant level. Econ staying on and service ac will stay on too. Sounds like you didnt put enough r134a in the system. How much r134a did you add? Capacity is 38 ounces(thats
with R12), and a bit less than that for r134a.

well in that year they used r12 refrigerant ! today they use r134a refrigerant they are not interchangable if you have already converted to r134a they you can call toyota and ask for specific amount although you really dont need to know all you need is a can of r134a with a gauge on it if it
75-80 degrees outside the pressure should be between 40-45 pounds if its 85-90 degrees between 45-50 pounds on the low side were you add it so basiclly keep adding till those pressures are reached

please do not add r134a if you have not had system converted over from r12

The A/C system is most likely low on refrigerant. A pressure switch will disengage the clutch on the compressor if it drops below a certain point. The compressor will not need to be removed for conversion to 134A. The conversion kits are available at most automotive retailers in addition to leak detecting and fixing agents which can be introduced into the system. It is very important to identify the low pressure access point in order to use these products and read all the safety warnings before attempting this on your own.

To convert from r12 to r134a freon, you first need to have the r12 discharged into a recovery system by a licensed professional. It is a violation of federal law in addition to environmentally irresponsible to vent this gas to the atmosphere. Next, remove the drier from the a/c system and use a spray can of a/c system flushing solvent to flush the oil r12 refrigerant and lubricating oil from the system by spraying into one of the liberated hose ends and placing a catch bucket under the other hose end.
You will need to purchase and install a set of adapters for the high and low side access valves by simply screwing them tightly and securely on top of your old r12 valves which are already in place.
After cleaning the system, replace the drier with a new one and reassemble the system. Evacuate the system to a sufficiently low pressure using an HVAC vacuum pump and then add the recommended amount of r134a freon and lubricating oil to the system through the charging hose on your combination manifold gauge set. Assuming of course that you didn't have leaks in the system before you began the conversion, you should now be good to go!
Good luck, and Stay Cool!

there are two hoses coming out of the firewall side by side .. one is large and one is small ... they both have valve ports but only the large tube (low pressure side) is to be used for adding refrigerant .. if your connector from the R134a can does not fit ..then you probably have the older R12 system .. that has been outlawed now because of ozone layer destruction caused by it ..you cant get that anymore .. you can however convert your system to R134a but it involves washing out the entire system and replacing all rubber parts ..then attaching adapters so the R134a will connect (availible auto parts) .. by law any remaining R12 in your system has to be recovered, not vented to air .. (actually the r12 is worth a fortune right now but it may not be legal to sell ..its about a 25 times increase) ... the modification process requires a "certified" tech to do the work and the results wont be quite as good as the old r12 ... at least it will work if the system is cleaned out enough .. the two refrigerants dont like each other .. that is, the lubes that are used do nasty things when mixed .. if you wanted to you could become "certified" by attending some classes and passing a test on ozone layer depletion ... now they have discovered that r134a is a powerfull green house gas .. so that also will be phased out in the future .. its like 1600 times worse than CO2 ... r12 was a wonderful chemical .. very hard to beat its performance and stability .. .

It came from the factory with R12 but look and see if it has already been converted to R134. If not then convert it over the R134 as R12 is very expensive. If it is low then you have a leak that must be repaired before adding refrigerant. It is illegal to add refrigerant to a leaking system.

you need to have your system evacuated ac a service center i wont pay more than $5o for that cause u got r12 in there n u cant buy that anymore then u need r134a fittings to go on urs napa has the good ones i wold charge yourself case theyll charge $70 dollars a lb for r134a that u can 4 $7