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post #1 of 11 (permalink) Old 08-29-2012, 05:07 PM Thread Starter
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High side gauge only goes up half way up

If you're really into automotive A/C you might have run into the situation that when filling with refrigerant, the low side gauge needle goes up as normal but the high side gauge goes only about half way.

As luck would have it my 1989 Haynes automotive A/C book gives numerous reasons as to what could be causing this. I've narrowed it down to either (a) stuck high side thermostatic switch or else (b) the expansion valve is stuck closed.

(a) Does the thermostatic switch actually close off - or partially close off - the refrigerant flow? Or?

(b) Where is the expansion valve located? In my case this is for a factory A/C equipped '75 Alfetta GT - which I understand is identical to the GTV6's. The fix is to spray refrigerant on the switch, but I recently bought a can of Freeze-Off so will use that. I'm in the midst of taking another vacuum test but will remove the thermostatic switch and take a look at it.

******
Should you be bored out of your mind, read the stuff below:

I've done this in the past, but my first try in filling the system with my new condenser installed worked great in that the temp at the outlet was 54. Unfortunately oil and refrigerant were leaking past some coarse threads about as fast as I was filling it.

The extension with coarse threads was strictly a means of extending the length of the low side fittings on the condenser. It was not what is called metal to metal regarding A/C fittings which fit into one another (got that?). So I soldered the threads.

After running the vacuum pump and letting it sit for an hour to verify no leaks I filled it with the first can and the both the low and high gauges were functioning as they should. But on the second can it was only a half way up on the high side and had about 64 at the outlet.

Thus the questions above.

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post #2 of 11 (permalink) Old 08-29-2012, 07:32 PM Thread Starter
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For now the bottom line is that the A/C is 60 degrees, two degrees lower than with the original 1975 condenser.

I got the high side up higher, but it still needs to get up even higher. I'd sure like to know what is blocking it since I feel there might be some extra minus degrees to be had and on the series of 95F degree days here, it would be most welcome.

I have no idea what the high side thermostatic switch on the dryer/accumulator is supposed to do, but that would be good information.

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post #3 of 11 (permalink) Old 08-29-2012, 07:33 PM
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Still don't understand why you soldered a fitting. Did you check to see if there was galled aluminum in the threads?

Also, when you're talking about pressures, need the exact readings. Half-way up doesn't mean much to me.

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post #4 of 11 (permalink) Old 08-29-2012, 07:58 PM Thread Starter
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The fittings were all steel. This particular fitting did not have a round gizmo which fits into the concave gizmo. Just a pipe thread. Trust me, it needed to be done.

Low side is 40, the high side was stuck at 175, it came up to 225 late today, but should be around 350.

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post #5 of 11 (permalink) Old 08-30-2012, 04:31 PM
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Like to get the low side down in the 30s, but 350 on the high side sounds way too much. More like 250 max. What Alfa tech data do you have on the system and where are you getting the 350 psi target?

The switch on the drier is most likely a trinary pressure switch that turns the compressor off when the pressure gets too high or to low, and also to turn on the electric fan on the radiator/condenser.

Are you using a R-134 expansion valve or the old OEM valve?

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Last edited by Roadtrip; 08-30-2012 at 05:14 PM.
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post #6 of 11 (permalink) Old 08-31-2012, 01:17 PM Thread Starter
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History: several years ago I had a series of discussions with an engineer email friend who had installed R12a in his GTV6 which I've assumed has about the same 'volume as the Alfetta's. 12a is a combination of propane and isobutane and is compatible with both 134 and older R12 systems. He has advised me on a number of the issues, but for the life of me I can find no place where he said that the low side should be 35 and the high side should be between 350 - 400 psi, however that is how I have those areas marked on my gauges. I'm sure I would not have used these marks without this fellow's advice.

I'll add that, for now, I'm at a loss as to how I have the high side switch on the dryer wired, except I know the black wire goes to 85 (which in turn goes to ground) on the A/C relay. The original A/C did not have a thermal switch.

The condenser comes on and stays on when the compressor is switched on. I'll add that I don't believe that the compressor cycles on and off - perhaps because the vent never gets below 60 degrees.

The A/C as it is now simply does not 'feel' right in that it wants to kill the engine if not kept at the very least 1000 rpm and the car overheats even when moving. Prior to this with the old condenser, it also needed to be kept close to 1000, but if the engine died, it didn't go into the convulsions that it now does. I'm no longer using the A/C until I get things sorted out.

FWIW, one 6 oz. can of 12a is equivalent to 18 oz. of R12 (or 16 oz. of R134).

Question: When adding oil, does that count towards the system's 'volume'?

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post #7 of 11 (permalink) Old 08-31-2012, 05:50 PM
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That's a very important point that you're using ES-12, and not R-134 like I thought. I have used ES-12 before, very successfully in a 85 Jeep A/C. The good thing about it is that it's a function drop in for R12 (but regardless the EPA says it's not), is compatible with R-12 mineral oils and expansion valves, and works great generally. The bad point is that it will burn under a narrow air/fuel ratio range.

Also, ES-12, or any of the HC based refrigerants operate at a lower pressure than R-12, and certainly not 350-400 psi. It supposedly has 33% lower pressure than R-12. When I used it in my Jeep, I think I was getting high side pressures of 200-210 psi or so, with low side pressures of 30 psi, and great cooling.

I'm not familiar with the Alfetta A/C, but are you talking about a "Thermal" switch, or a "Pressure" switch? The pressure switch will be off a port usually attached to the drier, but not always. A thermal switch will be a temp probe in the evaporator to cut off the compressor when the temp switch senses a freeze-up of the evaporator.

In any case, do you know exactly how much oil is in the system? I did you drain the compressor and condenser and install a new receiver drier?? And no, the oil quantity (for example the 164 uses 4.8oz of oil total in the system) does not count towards the refrigerant capacity. And you are correct that it takes much less HC refrigerant than R-12. And as I recall (check the website to be sure) ES-12 is charged as a liquid (can upside down).

Too much oil in the system, even if a little over the specified amount, compromises cooling. Is it possible you have too much oil in the system?

How much refrigerant did you put in? Do you have the capacity specs for the Alfetta/GTV6 system?

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post #8 of 11 (permalink) Old 08-31-2012, 08:06 PM Thread Starter
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My friend figures that since a Milano takes 36 oz. of R12, so this means 1.85 (or so) cans of R12a. We're going on the assumption that the Milano, early GTV6, and Alfetta GT have the same 'volume'.

My last filling was with one can of Oil Charge 3 which is 2 oz. oil and 2 oz. 12a and one can of R12a - which means I'm about 3 oz. low on refrigerant.

Now that I've changed condenser's, I have no idea if the 'volume' increased or decreased, or is about the same.

And as I mentioned in my first post, I had a major oil spill coming from the threads on the fitting that I later soldered (since teflon tape only slowed it down a bit).

The questions that I need answered: How much oil did the 'Sanden' compressor originally come with?

What type of high and/or low switch do I need and at what psi's should the switch turn off the compressor? And how should it be wired? Then the big challenge will be to find one that fits in my dryer.

I'm also confused as to the compressor cycling off and on - I gather to keep the interior at the temperature level of the setting of the compressor switch. Obviously this is an exaggerated fantasy for an Alfetta GT in that it might be too cold.

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post #9 of 11 (permalink) Old 08-31-2012, 10:33 PM
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So what I've gathered is that we really don't know how much oil is in the system between the leak and what ever was residual. Did you drain the compressor of oil before charging?

Last year I got a new Sanden compressor and it came pre-charged with 7oz of PAG oil, which is way too much for a 164 system. I drained it all and put in 4 oz of POE. I'm purely guessing now, but lacking all tech data, the Alfetta system might take about 4oz of oil total. I wouldn't think that a new condenser would add much, if any, refrigerant volume to the system, although unless drained they can hold about 1oz of oil.

As far as the compressor cycling, at what low and high side pressure does the compressor cutout, then come on again?

You might take a look at some of the tech questions/data on vintageair.com and nostalgicairparts.com. They make generic systems for hot rods and you might get a few tips from there.

I know I'm not much help, but if I had the tech data for the system, I'd be more useful. Look on the side of the pressure switch. Sometimes it gives the psi triggers right there. If not, a make or part number might help track down the specs of the switch.

Right now I'm thinking that you might need some more refrigerant, but that's only a guess.

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post #10 of 11 (permalink) Old 09-01-2012, 12:07 PM Thread Starter
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John, as you can see below, removing the compressor to drain it (no drain at the bottom) and measure the amount of oil is not an option unless it became a do or die situation.

This is apparently official Sanden info. My compressor is a SD-508 (why I didn't get the SD709 one is beyond me - same price - New Sanden Style 709 V- Belt Double Groove - Compressors)

6.8.1 Oil Flow Theory
Compressor lubrication occurs as the oil which circulates with the refrigerant passes
through the compressor crankcase during operation. The Sanden SD series
compressor achieves optimal durability and cooling performance when oil circulates
through the system at a ratio of 3.3% to 8% oil to refrigerant. Excess oil can act as an
insulator limiting heat transfer in the evaporator and condenser, while too little oil can
negatively affect durability.
Oil will collect in low pressure cool components (evaporator, accumulator and suction
hose) of the refrigerant loop. For example a long suction hose which sags can collect
several ounces thus reducing overall oil circulation ratio.
6.8.2 Oil Charging
6.8.2.1 Passenger Car, Light Duty Truck Single Evaporator
Refrigerant charges 24oz (680g) to 40oz (1133g)
135cc oil TXV systems
240 cc oil in orifice tube systems

Now, do I have a TXV or oil in orifice tube system?

And...even if I drained the compressor, how much oil is in the rest of the system? And...how many ounces are there in two 18" diameter puddles on smooth concrete?
Also...I've run the vacuum pump three times. How much oil does that remove or is the oil heavy enough that it doesn't get sucked out?

I'll admit I'm fairly seriously thinking of getting the SD-507 compressor, knowing it will be a direct bolt on...and not have to worry about how much oil is in the system.

As it is, if I have a TVX system and going by the 36 oz. figure as the capacity of the system, I'd need 4.5 oz. of oil. I've added two oz. Perhaps another ounce? I was told that the oil plays a big part in cooling the system, providing you don't overdue it.

I've confirmed that the + wire from the pressure switch goes directly to the compressor clutch. Since the ground wire goes to the relay, I'm assuming the + wire then doesn't need to?
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post #11 of 11 (permalink) Old 09-01-2012, 04:07 PM Thread Starter
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Do not try this at home...

After realizing I had a major crack in the low side hose and wrapping it with a lot of electrician's tape, I added more refrigerant - I have no idea as to how much. After jumping up high the low side came down to just a hair over 30 and I simply watched the high side until it seemed to quit climbing at 240. I also checked the sight glass and I could see clear gas? liquid? flowing through it. There was no brown, so it told me I'm highly unlikely on the high side with the oil. The air was chilly coming out of the vents, but not icy cold.

And then...I shut off the engine and removed the low side hose using adjustable pliers since I tighten the hose fittings pretty tight. Then I began to undo the high side and the gas started coming out in a major plume, I turned away, took a big gulp of air and stayed until I could get it off. It felt like it was frozen on.

Bad, bad stuff to be breathing. If ever this stuff was going to blow up it was then since the very hot exhaust manifold as you can see above, is only about an inch from the high side filler/outlet. There was about an eight inch puddle of oil on the floor - not counting what was in the mist.

Big fan will be blowing behind me and I'll have on a wet Western robber's mask (hankie) next time.

I found the box that the switch came in and it is a low side switch for an '83 1.4 Honda.

I'm more worried about the high side and had I had one which was a high side, it might have been cutting out the clutch before it hit 240.

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