A/C pumped & refilled but still not right

reno · Jul 7, 2008

What else could be causing my A/C NOT to get colder than 62Degrees even at highway speeds? On the original label it says R-12 Refrig, 1.75lbs max, I was told here that 80% of R-134a which would be 2 12oz cans (24oz) 1lb 8oz. Is this to much or to little?

MAKG · Jul 7, 2008

If you just drained and refilled, there could very easily be mechanical problems such as circulating corrosion products, leading to blockage.

You really can't tell without a pair of gauges.

CraigK · Jul 7, 2008

Two factors may be contributing to your issue.

One is if the two 12 oz. cans of refrigerant you added came from an R-12 to R-134 conversion kit, then 2 oz. of each 10 oz. can was oil, not refrigerant, so you actually added only 20 oz. of R-134. (If they did not come from a conversion kit, who, when and HOW was your system converted? Was the system flushed of remnant R-12 and R-12 oil?) You might try adding a bit more R-134, if your pressure is still on the low side.

Also, converting a system originally designed for R-12 to R-134 will not give you back the original level of AC performance. Just isn't as good a refrigerant, in a system designed for a different compound. But R-134 conversion can be give more than adequate AC performance at a very reasonable cost.

CraigK

reno · Jul 7, 2008

P.O. said when I bought the truck he had the A/C lines replaced with original R-134a lines and the compressor replaced. I do not know what shop or person that did it. On the Gauges I know the Low side was reading around 45#, but can't remember the high side psi.

reno · Jul 7, 2008

MAKG said:
If you just drained and refilled, there could very easily be mechanical problems such as circulating corrosion products, leading to blockage.

You really can't tell without a pair of gauges.

What should I be looking for from the gauges? My biggest fear is I Did not pump the system enough. This is my first time pumping a system.

MAKG · Jul 8, 2008

If you suspect water contamination, check the gauge temperatures against what they actually are (use an IR thermometer). Water has a different vapor pressure and will change it.

If you suspect blockage, look for spiking high side pressure, and short on-cycle times.

If you suspect the pressure switch is screwing up (or is mistuned) check the low side pressure when the switch opens and closes.

And so on.

If you tried to use a venturi vacuum pump, you almost certainly didn't suck it down enough.

reno · Jul 8, 2008

Yeah the venturi sucks. That is all I had to use though. I will keep looking for a decent pump. Last one was needing a electrical cord to make it work and had to be changed over from a R-12 valve, he should have at least replaced the cord so I could test it, did not buy it. I need to get back with a tech I spoke with, he said his boss normally retires some pumps after a year or two of service and sells them cheaply to the employees. He will let me buy it from him at what he paid, he said sometimes prices go from $10 up to $50. Obviously a $10 will be well worn and in need of repair and $50 will work just fine for a home owner that occasionally uses it.

So with being said, I guess I will wait until I have a decent pump, then will just pull\inspect the orfice tube\replace with a new one. Pump the system for a half hour, close the valves and wait another half hour. then fill.

OH Yeah, just remembered, when I was pumping, I do recall hearing twice only, a "thud" sound in the drier, never did it again though, what is that? Water?

Gee Makg, I wish I could find the words easier to type shorter sentences like you.

MAKG · Jul 8, 2008

It's advisible to replace the drier (again).

But if you aren't going to, I'd suggest sucking it down quite a lot longer than 30 minutes. Like, overnight.

I don't know what that "thud" might have been, but I'd suspect it isn't good.

shadetree · Jul 8, 2008

Be sure and use a red orifice. Blue one doesn't cool as well. shady

MAKG · Jul 9, 2008

shadetree said:
Be sure and use a red orifice. Blue one doesn't cool as well. shady

FYI, reno, the color encodes the diameter of the orifice.

Red is smaller than blue. It will maintain a higher pressure differential, with a smaller refrigerant flow rate.

This time around, I put a blue one in my air conditioner. I've put red in before. I'm having a hard time noticing the difference, though I'm sure it's there.

Just don't put in those "adjustible" ones. They cost 30 times as much and make it really hard to read cycle times.

reno · Jul 9, 2008

Understood, thank you.

AllanD · Jul 15, 2008

The best way to pump down a system with a suspected "wet" receiver drier is to pump the system down, then take the truck for a drive.

when you come back pump it down again while the engine bay is still hot.

the heat and the vacuum will drive the moisture from the dessicant very effectively.

Another method that can work but requires skill in fabricating lines is to make up plugs for the receiver drier and pump it down with you vacuum pump while it is sitting ina 250deg over or bobbing in a pot of boiling water.

trust me, the dessicant WILL give up it's moisture.

I Have a Robinaire recycler and I pumped my truck's system down every
night for two weeks before I was happy with it.

and I still blew a 6oz can of system sealant into it after
pumping it down again because it leaked down between September and january.

This was with NEW lines, new Condenser, new evaporator and replacing
every o-ring in the system (and putting a dab of silicone grease on each point)

Yet now even going "hunting" with my battery powered blacklight I can't
find any leaks (The stop leak I used has flourescent dye)

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