Full charge after only half the freon?

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kenneyd
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Joined: Tue Sep 01, 2020 4:28 am

Full charge after only half the freon?

Postby kenneyd » Tue Sep 01, 2020 5:12 am

Howdy,
Kind of confused at the results after helping out a friend with his suburban. Basically the high/low pressures seem to be right on, but only after adding about half of the freon capacity.
Just a little background, I'm just an enthusiast with a private shop, I've fixed or replaced several AC systems in my own cars, everything has always seemed to go as expected.

I have a friend with a 1988 suburban with a 6.5 l diesel swap, he took it to a shop to have the AC charged, apparently they screwed around with it for a little bit, then they basically refused to work on it anymore, so he asked me for help. About a month ago I had just finished installing a factory AC system on my 1984 m1009 (K5 Blazer). So I was fairly fresh on the procedure..

The The suburban is basically a bastard, the compressor was installed about a year ago, but never hooked up. It was a ACDelco HT6 compressor.
After the shop looked at it, we replaced the condenser evaporator, accumulator with aftermarket parts from RockAuto for a 1988 vehicle, and the rear AC is a 'vintage air' aftermarket kit..

The first time he brought the truck over, he claimed the shop had put oil in it, so I pulled a vacuum on it, and began to charge it. I knew my K5 Blazer was perfect after 3.5 cans of 134a, so I just began filling his system.
Near the end of the 3rd can, I looked at the gauges and the low side was about 55, and the high side about 250. Outside air temperature about 85. My 134 a chart said it should be 40 to 50, and 175 to 210. Something wasn't right. I decided to just stop, and go search the forums for some answers. And try again a different day.

Apparently he used the AC on the next few days and then he told me the AC clutch had quit.

So go out there and inspect it, and the AC compressor is seized. Great.
We throw a bunch of new parts at it, I completely disassemble all the components and flush it all. We install a new four seasons HT6 compressor.
This time I add the exact amount of oil in.
I pulled a vacuum for 30 minutes... all good, so I charged it.
according to the service manual, it should take 54 oz of r12. I've always found that that translates to about 20% less r134.

I estimate we put in approximately 30oz, and the pressures are now 45, and 185. At 80 degrees outside
System seems to be running normal, and cooling pretty well. I am fearful of adding more.

I guess I'm looking for opinions on why it's only taking 30 oz?
I guess I'm still baffled, however I think I'm going to chalk it up to just a unique system. All of his lines under the hood are custom, a mix of parts from different years and aftermarket systems who knows.

As for why the previous compressor failed, I'm not sure how the compressor was cared for for the last year, or if it was ever exposed to the elements. He indicated to me that the shop "thought they overfilled the oil", but they didn't want to charge it cuz they thought "there might be a clog" etc etc I really know idea.

Basically, I hate working on other people's cars lol.
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Cusser
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Re: Full charge after only half the freon?

Postby Cusser » Tue Sep 01, 2020 6:41 am

Maybe someone sealed off the lines to the rear evaporator on the Suburban?
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JohnHere
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Location: South Carolina Upstate - USA

Re: Full charge after only half the freon?

Postby JohnHere » Tue Sep 01, 2020 7:35 am

Cusser wrote:Maybe someone sealed off the lines to the rear evaporator on the Suburban?
Good thought. And I would ask: Is the rear A/C working?
kenneyd
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Joined: Tue Sep 01, 2020 4:28 am

Re: Full charge after only half the freon?

Postby kenneyd » Tue Sep 01, 2020 8:07 am

JohnHere wrote:
Cusser wrote:Maybe someone sealed off the lines to the rear evaporator on the Suburban?
Good thought. And I would ask: Is the rear A/C working?


Not blocked, his rear AC is working great.

I will add that he is using the same condenser, evaporator, accumulator as I am and are compressors are very similar. His is a serpentine belt driven HT6, and mine is a v belt driven. My blazer does not have rear AC, and for sure I have right around 40 or 42 oz in mine, and my pressures are perfect.
Al9
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Location: Southern Europe

Re: Full charge after only half the freon?

Postby Al9 » Tue Sep 01, 2020 8:41 am

Keep in mind that when the refrigerant is just a little low, the system might still perform satisfactorily but the compressor could be running oil starved. And HT6s are really reliant upon proper oil return rate. This gets critical if there's rear AC. Rear AC can basically turn into a refrigerant and oil pool when the rear blower is left off.
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JohnHere
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Re: Full charge after only half the freon?

Postby JohnHere » Tue Sep 01, 2020 10:21 am

About 30 ounces of R-134a does seem a little light. I think it should be around 32-38 ounces based on the R-12 spec. Did you weigh-in the charge or estimate using the small cans? If the latter, it's possible that you charged more than you thought. The pressures look pretty good now. What are the vent temps?
kenneyd
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Re: Full charge after only half the freon?

Postby kenneyd » Tue Sep 01, 2020 10:32 am

JohnHere wrote:About 30 ounces of R-134a does seem a little light. I think it should be around 32-38 ounces based on the R-12 spec. Did you weigh-in the charge or estimate using the small cans? If the latter, it's possible that you charged more than you thought. The pressures look pretty good now. What are the vent temps?


Using 12oz cans.
I did not have my thermometer with me last time I saw the truck so I can only guess.
The rear did feel better than the front, but then again his front box was a mess. Probably under 50 in the rear.
kenneyd
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Joined: Tue Sep 01, 2020 4:28 am

Re: Full charge after only half the freon?

Postby kenneyd » Tue Sep 01, 2020 10:33 am

Al9 wrote:Keep in mind that when the refrigerant is just a little low, the system might still perform satisfactorily but the compressor could be running oil starved. And HT6s are really reliant upon proper oil return rate. This gets critical if there's rear AC. Rear AC can basically turn into a refrigerant and oil pool when the rear blower is left off.


So always have the rear on when the front it on?
Al9
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Location: Southern Europe

Re: Full charge after only half the freon?

Postby Al9 » Tue Sep 01, 2020 12:54 pm

Exactly. At least minimum speed.

If i owned that vehicle, i'd rewire it so that the rear blower is always running at least at minimum speed whenever front AC is on. Exactly like with my front AC-only little Kei car (a relay behind the dash keeps the blower on at minimum speed even if you rotate the fan knob to 0, when AC is on) and like i've seen the driver's AC work on a city bus (passenger blowers switch on at minimum speed when only the driver's AC button is pressed on the dash).
kenneyd
Posts: 6
Joined: Tue Sep 01, 2020 4:28 am

Re: Full charge after only half the freon?

Postby kenneyd » Tue Sep 01, 2020 12:57 pm

Al9 wrote:Exactly. At least minimum speed.

If i owned that vehicle, i'd rewire it so that the rear blower is always running at least at minimum speed whenever front AC is on. Exactly like with my front AC-only little Kei car (a relay behind the dash keeps the blower on minimum speed even if you rotate the fan knob to 0, when AC is on) and like i've seen the driver's AC work on a city bus (passenger blowers switch on at minimum speed when only the driver's AC button is pressed on the dash).



I sent the guy a text letting him know this, he said that he had heard about this already, and always has the rear AC on anytime the systems on.

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