problem measuring a/c high side pressure

[JDEstill]

Well, since ya'll are so curious...

- The last 2 times I have had the engine out of the car (last time was 6 years ago I think) the a/c has lost its charge. I figure that laying the compressor back, hanging it off the frame or something with some wire, kinked one of the hoses enough to let some freon escape past an o-ring or something. Just a theory - all I know is once I get the engine back in, it had lost its charge. Happened to me twice.
- That being said, the first time that happened, I had the system charged back up, and it held that charge until I took the engine out again. Shop put some green dye in with some freon, and that green dye never showed up and is still in there (saw evidence of it when put freon in a few weekends ago). Next time I had the engine out, 6 years ago or so, it depressured again, and that time I just didn't mess with it. Till now.
- There was still some pressure in the system. Because of that I am willing to risk that no air got in. If it was completely unpressured, then yeah, that would be a bad assumption. But air usually doesn't flow from low pressure to high...
- Buddy of mine has a 30 lb tank of R-12, and said I am more than welcome to what I need. Offered to pay, but no no, he's just happy to help. What a friend
- So that being the case, then yeah - I decided to try charging the system back up with R-12 and see how it works! If it holds pressure and stays cold, then I am golden. If it leaks down again, I will find the leak, fix it, replace the drier, replace the orifice tube, pull a vacuum and make sure it holds it, and convert the whole thing over to R134a (or something else if something else has come along by then - because I probably won't have the motivation to do all that for several more years).
- It's been a couple of weeks and so far it is still blowing cold. So if it does have a leak, at least it isn't a major one. But I still want to verify the pressures, and put more in (or take some out) if necessary. Compressor makes a funny sound every once in a while... I don't fully trust it.

 

[RmvBfrFlght]

and convert the whole thing over to R134a (or something else if something else has come along by then - because I probably won't have the motivation to do all that for several more years).

Use ES-12a, it is here now and is a drop in for R12. No flushing and changing the oil, o-rings, accumulator and so on. Unless the system was open no need to even vac it down, just fill it with the ES-12a. It is also much less expensive then R-134a.

To legally fill a R-12 system with ES-12a, it first needs to be converted to R134a. Easy enough to do: install the conversion fittings, wave a can of R134a over the system, and fill with ES-12a. No muss, no fuss.

Can you tell I like this stuff?

RemoveBeforeFlight

 

[JDEstill]

Back again at last! Weird thing - I planned to try and find that high side adapter I needed so I could hook my gauges up and read both high and low side pressures, but just never got around to it. Then earlier this week, as I was rooting around in my drawer of misc brass fittings... there it was... huh, I thought, what is that thing? That looks just like the a/c adapter I need... tried it with the gauge set - yup, fits the gauges. Tried it on the car, yup, the other end fits here. How I ended up with this thing, no idea - probably had it for years. Did not have a clue. But happy days, now I can actually check some pressures!

So, today I did that. R12 as I mentioned before. Pressures on both sides without the compressor running were 115 psig. Turn on the a/c, low side went to 125 psig, high side went to 190 psig. I haven't gone looking to see what the pressures *should* be, but my gut says the low side pressure is too high and the high side pressure is too low. My gut could be wrong So anyone want to be extra helpful and tell me what the pressures should be, and if mine are off, then what do my pressures say is wrong?

Thanks guys

John

 

[charlief1]

Low side should be between 40 and 50 PSI. This is with the fan on high and setting is on max AC. Windows open as well

 

[JDEstill]

So if mine isn't 40-50 psig... what's the diagnosis, Dr?