R-12 is easy to check the refrigerant level. Look at the sight glass (at the drier, very close to the low pressure switch) with car running and A/C on. It is a small clear window, about 1/4” round at the very top. If you have the compressor jumped, via jumper wire, or as you said via a suicide cable, and with engine running, you can take a flashlight and looking through the sight glass on the drier, it will be either blank or you will see bubbles.
If you have bubbles, then your level is low.
If you see nothing, then you have a good level or you are empty.
This doesn't work as well with dye in the system – but still works. Note, using the sight glass ONLY works with R-12. The other refrigerants do not work the same way.
Note: most all new driers (for our cars) are built with the sight glass present – but typically are painted over. If using a new drier for a R-12 system, just take something to scratch off the paint, but don't scratch the glass. You can then charge the system until the sight glass goes clear, then add about 1/4th to 1/2” can (or pound) additional and you are done. No gauge set or weight scale is required (but is still recommended, if you have access to one).
When they went to R-134a, they took away the ease of working on A/C systems.
Granted, working with a refrigerant station is WONDERFUL, but overall, is still a pain. The refrigerant stations, you can dial in how much to install, push a button, and go do something else – as well as recover the existing refrigerant as well.
A/C compressors are meant to be used every so often. A minimum of once every year. Best is to run the A/C a few minutes every 3ish months or so. If you don't, the front compressor seal will either leak or go bad. The odd thing is, the A/C compressor front seal are made of ceramic – which is something I think is funny. Really, something that is “rock” hard is meant to hold back pressure?? It is just not logical to me – but it does work, and it requires refrigerant oil to keep it lubricated (which IS the reason why to cycle the A/C every so often).
The good news is it is not too hard to convert our cars to R-134a (if using either the RV-2, Sanyo or C-171) compressor.
For longevity sake, the boat anchor (the RV-2 compressor) is built like a tank and is one of the very few A/C compressors made with an actual oil pump.
For fuel mileage, the Sanyo or C-171 is your choice, but neither version will give you a lifetime of service like the RV-2 will.
First, we need to find your leak. I suspect the most likely cause is the compressor front shaft seal – but could be wrong. You need to confirm you do not have other leak(s) in system before performing any repairs. To do that, you need to will need to add dye to the existing system, preferably add more R-12 to the system, then drive car while using A/C to find that leak (with a black light).
Once all of your leaks are found, then converting your existing system to R-134a is not too terribly hard to do - but is labor intensive. A new drier and all new seals/gaskets are needed. Also flush solvent (which is expensive stuff, but required) as well as new A/C service ports.
Next, flushing out all remnants/traces of the old refrigerant oil IS MANDORY. The oil used for R-12 and R-134a highly disagrees with each other (think of putting hydrogen peroxide on a body cut on how it boils up). This is where the labor and persistence takes place because you have to work hard to get all traces of oil out. If you do it correctly and thoroughly, you will only have to do it once.
I recommend removing the compressor from the car, then remove the oil pan so you have access to perform a thorough cleaning. If, by chance, your front seal is leaking, this would be a great time to fix that, as well. I do not recommend using flush inside of the compressor. I recommend using (dried/filtered) compressed air. If you use paper or cloth inside, try to use something that will not leave any lint behind.
Most of the oil (maybe 2/3rds of it) will be inside of the compressor.
Removing the evaporator core and condenser is also highly recommended to remove first to perform a proper flush. The condenser can be done in car, but the evaporator core is a hard one to clean.
R-134a
Once converted to R-134a, it will hold 31 to 32 oz.
The (new) refrigerant oil to use will be 13 oz, “PAG 100”.
Any new rubber O-rings need to be R-134a compatible. Any O-rings not touched can be left alone.
If you have a hose leaking, the new hose will need to be R-134a compatible. Any old hoses can be reused if flushed out well.
Use a drop of PAG oil on your new O-rings and gaskets.
Use of (new) metal gaskets is fine.
Some recommend getting your old compressor rebuilt or replaced - just to make sure no old oil exists. That is not a bad idea, especially if your front shaft seal is leaking - but the cost of a replacment compressor (or rebuilding) might be a bit more than one might expect (maybe). If you are considering that method, just know I would be very interested in your old RV-2 compressor
R-12
It would be best to re-use R-12, if you can find any.
Your vehicle, if using R-12, will hold 42 oz (2-5/8 pounds).
R-12 uses mineral oil (only), 13 oz.
R-12 will not require to flush the A/C system (unless you have metal contamination – which is extremely uncommon with the RV-2 compressor).
Use a drop of mineral oil on your new O-rings and gaskets.
Use of (new) metal gaskets is fine.
BudW