R134a conversion - problem, or unrealistic expecations?

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R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Fri Jul 22, 2016 10:17 pm

Vehicle: 1988 Chevrolet 3/4 Crewcab (73-87 body style)
Engine: 2005 GM 6.0L V8
Compressor: Denso 10S17F
Orifice Tube: Ford Blue
Condenser: ACDelco Parallel Flow (156960)
Temperature: 93F w/ 45% humidity
High side: 325-350
Low side: 45-50
Center vent temp, at idle, max air, doors open: 60F
Center vent temp at 55mph, max air, doors closed: 52F


Hello all,

I just completed my A/C system on my engine swapped 1988 Chevrolet Crewcab, and I have to admit, I'm not entirely happy with its performance. The system is all new except for the evaporator, which was flushed. I used a Ford blue orifice tube, 8 oz of PAG46, and the shop that charged it said they only had to put 32 oz of R134a in the system. I vacuumed the system immediately after buttoning everything up, and the accumulator was the last thing installed. The A/C shop also vacuumed before they charged, per standard procedure. The accumulator and outlet fitting are sweating, and the suction line fitting at the compressor is cold/cool as well. Compressor discharge is hot, condenser outlet is warm. The evaporator inlet, at least where I can feel before I run out of visible tube, doesn't feel all that cold, just cool. At idle, pressures were about 45-50 low side, 350 high side. I am running 2 LT1 Camaro e-fans with proper fan shroud, and they come on with A/C pressure as they should (controlled by the PCM). Spraying water on the condenser dropped it to ~300-315, which is somewhat expected? At 1500+ RPM, the pressure would quickly rise enough to cut off the compressor via my HPCO (~455 psi, according to the spec). The cooling is OK, but seems like it should be better with a parallel flow and modern compressor. Once the sun went down, I took it for an extended highway drive, and the lowest temp I saw while moving was 51-52*. It actually got slightly cooler at idle - 49* or so. Temps were still in the 90F range.

Am I just expecting too much from the system, or is something wrong? Based on some troubleshooting guides I saw, high low side and high high side pressures could be caused by a non-sealing orifice tube. While filling the evaporator with some of the oil charge, some started to run out (evaporator line is level, shouldn't have tried to put oil in it, haha), so I used compressed air to blow the oil into the evaporator, and I accidentally "sealed" the blow gun against the tube. Did I blow my o-tube backwards into the liquid line, possibly?

Let me know if there is any other info I can provide.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Tom Greenleaf » Fri Jul 22, 2016 10:30 pm

A cobbled set up but working so can just say know the actual air temp coming in thru grille as high side is a bit high and so is low. If all else is right, plenty of fan power you should see lower pressures and lower temps but not a wild difference.

Bet you could drop that a few degrees tweaking the charge amount - I do and it can take forever to pin just right with an unknown capacity.

In short first try water on condenser for a drastic change it would drop pressures some anyway. Gives a clue how well condenser is transferring heat.

I think you can't drop vent temp at idle after it's run for some time and everything closed down to 50F at least or lower than 60F at least and better on highway as well,

T
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Re: R134a conversion - problem, or unrealistic expecations?

Postby cornbinder89 » Sat Jul 23, 2016 1:05 am

High side says your condensing temp is too hot, 165 to 175 deg's. Even watering it down didn't drop it to where I think it should be. I'd want to see high side with wet condenser no higher that 170 psi.
Why did you mix/match parts? I would stay stock, than you have a baseline to go from.
My experience with conversions is to concentrate on the condenser, Get as much heat out there and the systems seam to work fairly well, have marginal heat loss at the condenser and it will never cool right.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby GM Tech » Sat Jul 23, 2016 2:55 am

Did you double check to make sure there was NO orifice tube in the condenser outlet pipe-- that was/is the standard location on a c/k GM truck...you may be running two orifice tubes by mistake....
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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Sat Jul 23, 2016 4:16 am

I wanted to keep the engine package "stock" looking, no aftermarket brackets or anything. That ruled out the commonly available brackets they make for adapting the R4 to the LS engine. Also not a fan of the R4, though admittedly the one on my 91' Caprice works well, even with R134a, and it's original.

I can hold on to the condenser outlet, it's hot, but not too hot to touch. The condenser inlet is too hot to hold on to. The condenser is a parallel flow "direct replacement" from ACDelco, but it is actually smaller in dimension than the original condenser. Do you suppose I just need to move to an even larger parallel flow condenser?

GM Tech, no double orifice tube. This truck, even though it's an 88', is the older body style (R/V truck) with the o-tube in the evaporator, the crewcabs and 1 tons stayed the old body style until 91'. I put a new condenser in it myself, so definitely no orifice tube there. I also personally installed the blue orifice tube into the evaporator. Short screen is towards the evaporator, long screen towards liquid line.

I found these notes in Spectra Premium's A/C guide:

PRESSURES TOO HIGH
HIGH SIDE
A. air flow through the condenser; check gaps around the condenser, folded over fins
B. check fan clutch or electric fan operation and check for correct rotation.
C. Also check fan shroud for leaks or gaps.
D Radiator not cooling, or touching condenser, transferring heat into A/C system
E. If recently serviced, may be overcharged or have air in the system
F. Blockage in the top of the condenser or in the discharge muffler; after the gauge
port
G: Big Transmission cooler attached to the condenser
H: Missing or bypassing Orifice Tube


LOW SIDE
T. Orifice tube or TXV not installed correctly, or stock open, allowing excess refrigerant
into the low side

V. Blockage in the suction line after the gauge port, not allowing the compressor to
suck down the low side.
L. Compressor not pumping properly
E. Air in the system
S. EPR stuck open (if equipped)
PS/TS. Cycling switch (pressure or thermal) turning compressor off too soon


Based on that, is there a possibility that an o-tube that's not fully seated could be causing my pressure problems? Or does it lean more towards a possible overcharge condition?
Last edited by foamypirate on Sat Jul 23, 2016 4:30 am, edited 1 time in total.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Sat Jul 23, 2016 4:22 am

Not sure if it helps with anything, but here are pictures of the setup. It's a bit messy at the moment, still finishing up the tidy details of the swap. :lol:

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Re: R134a conversion - problem, or unrealistic expecations?

Postby cornbinder89 » Sat Jul 23, 2016 7:05 am

Why the "Ford" OT and not the one it calls for?
I'd say that you might have too much 134a in it or a defective condenser, If the outlet is well below the temp the high side is indicating, Either the condenser is full of liquid 134a, making its effective area smaller( overcharged), or some of the tubes are plugged making the effective area smaller. Non condensable (air) is another possibility.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Tom Greenleaf » Sat Jul 23, 2016 8:47 am

Quote on just one thought here, ">>

I wanted to keep the engine package "stock" looking, no aftermarket brackets or anything.<<"

I think you way past too late for stock "LOOKING."

Rust shown in pic is unfortunately stock looking for that era of GM trucks yet it survived by where it has been.

Just tweak up A/C with assorted parts now to the best it can be and think you are close. If the pics of condenser are the way you are testing anything it's not ready - too much air can get around, under or miss the thing,

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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Sat Jul 23, 2016 2:21 pm

I did say stock looking, not factory, haha. I just didn't want to hang a bunch of bling and billet bracketry off of the thing; it's not a show truck. I wanted a clean looking install, as if GM had installed that engine originally.

Ford OT was installed due to some historical threads I found on here recommending it for R134a conversions, and supposedly helpful for around town cooling vs. the GM white .072 tube.

I'll see if I can't have a few oz. of charge taken out of it and see what the pressures do. Another theory I had bounced my way is that perhaps the charging shop added another charge of oil before adding refrigerant. I already had the oil in there when I took it by. They didn't charge me for it, so it seems somewhat unlikely, but you never know.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Cusser » Sat Jul 23, 2016 3:12 pm

You say you changed out the engine - so do you have adequate shrouding around the condenser/radiator fan ??? Important.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Tom Greenleaf » Sat Jul 23, 2016 3:18 pm

I'm at CarJunky too as you've noticed so just comment on the oil here now:

If somehow there was too much oil pressures go erratic and not just 2 ounces but LOT too much. I dare say it settles in bottom of condenser so less efficient but can move at times and settle down later.

IDK - If you would try using water as a test on condenser it would help and you haven't said you had yet?

If you could just target lower one 5th of condenser and no change than it would be oil in there as my guess.

This as said all along just smacks of an overcharge so far if all else is adequate. It doesn't take all that much over to mess it up,

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Re: R134a conversion - problem, or unrealistic expecations?

Postby cornbinder89 » Sat Jul 23, 2016 3:39 pm

foamypirate wrote:Spraying water on the condenser dropped it to ~300-315, which is somewhat expected? At 1500+ RPM, the pressure would quickly rise enough to cut off the compressor via my HPCO (~455 psi, according to the spec). .

He did, and it didn't drop as much as would be expected, in my opinion
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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Sat Jul 23, 2016 3:57 pm

I think you are right on the overcharge, took a bit out of it, and the temps dropped 1-2* at the vent. Not much, but an improvment. I'll work some more on fine tuning the charge. The humidity was a bit higher this morning, and the suction port at the compressor was sweating, so I think it's boiling off to some extent in the accumulator and suction line as opposed to the evaporator. I also re-did the water test on the condenser this morning. It was around 275 psi at start-up for 84F and 60% humidity, but dropped to 225 psi with water, and the low side went down to 35 psi. After removing a small amount of refrigerant, it took much longer for the pressure on the high side to climb back up. I think I can improve that with some sealing foam between the radiator and condenser, as that definitely seems airflow related. Temps going down the road this morning, in morning sun, were 47-46* at the vent. Getting there!
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Tom Greenleaf » Sat Jul 23, 2016 4:00 pm

Sorry! I missed that. That suggests if no change or little condenser is defective or somehow already clogged some? Yikes - best only way to know is dump it!

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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Sat Jul 23, 2016 4:04 pm

Tom Greenleaf wrote:Sorry! I missed that. That suggests if no change or little condenser is defective or somehow already clogged some? Yikes - best only way to know is dump it!

Tom


I'm thinking I may not have put enough water on it. I just misted it with the sprayer from a few feet away. Didn't want to slug the fans with too much water. I re-did the test today and saw a drop from 275 down to 225 or so, before we took some of the refrigerant out of the charge. Things seem much more stable with the slightly smaller charge. The HPCO isn't tripping now, for one (though it is 84F vs 93F from yesterday).
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Re: R134a conversion - problem, or unrealistic expecations?

Postby cornbinder89 » Sat Jul 23, 2016 4:11 pm

foamypirate wrote:I think you are right on the overcharge, took a bit out of it, and the temps dropped 1-2* at the vent. Not much, but an improvment. I'll work some more on fine tuning the charge. The humidity was a bit higher this morning, and the suction port at the compressor was sweating, so I think it's boiling off to some extent in the accumulator and suction line as opposed to the evaporator. I also re-did the water test on the condenser this morning. It was around 275 psi at start-up for 84F and 60% humidity, but dropped to 225 psi with water, and the low side went down to 35 psi. After removing a small amount of refrigerant, it took much longer for the pressure on the high side to climb back up. I think I can improve that with some sealing foam between the radiator and condenser, as that definitely seems airflow related. Temps going down the road this morning, in morning sun, were 47-46* at the vent. Getting there!

Fine tuneing a CCOT system can be hard. A Tx system stores excess refrigerant in liquid form in the receiver, An OtCC doesn't have one, and any excess is held by the accumulator as low pressure gas, and the system handles it by cycling the clutch. This means the correct amount is a lot more critical with an OTCC system, too much and the high side pressure goes up and the condenser fills with liquid and has less area to condense the hot gas to liquid.
If it we mine, I would start over with the OEM spec'd tube and start by under filling and SLOWLY add 134a, letting the system stabilize before deciding if it needs more. The trick is stopping before you go much, if any past "ideal".
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Tom Greenleaf » Sat Jul 23, 2016 4:14 pm

OK - I don't mean flood with water - it's effective with a decent mist even.

Now lower pressure and mentioned HPCO doesn't cut out. How's the output at vent's now? How much did you remove?

Reason that's so important is at some point you'll want to do something and discharge system and the weather may suk and have no chance to get it right again then and go thru this whole hassle all over again later,

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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Sat Jul 23, 2016 4:24 pm

Tom Greenleaf wrote:OK - I don't mean flood with water - it's effective with a decent mist even.

Now lower pressure and mentioned HPCO doesn't cut out. How's the output at vent's now? How much did you remove?

Reason that's so important is at some point you'll want to do something and discharge system and the weather may suk and have no chance to get it right again then and go thru this whole hassle all over again later,

T


Started small, took 2 ounces out of it. I didn't want to make a huge change. It dropped the vent temps 1-2*. Primarily stayed right around 49*, but did drop down to about 46-47* by the time I got home. So I guess, it really dropped 2-4* depending on driving situation. It still cools better at lower engine speeds, which seems to make sense a bit with the overcharge (compressor moving more refrigerant, higher pressure in condenser, etc, etc).

I did get curious, and looked up the factory charge for a 2005 Sierra (the truck my engine and compressor came out of), and it's 1.8 lbs, or 28.8-29oz. In retrospect, this may have been a better baseline, or slightly below, for the initial charge.
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Re: R134a conversion - problem, or unrealistic expecations?

Postby Tom Greenleaf » Sat Jul 23, 2016 4:45 pm

You are about right if this was OE and the newer set up 100%. They jump thru hoops to come up with a charge to the 1/2 oz in some.

Not like the 88 OE truck you could be off a pound and it wouldn't care when newer.
134a is plain inferior refrigerant but the product used so we put up with it. It's BTU ability isn't close to what R-12 was along with a predictable range of behavior all at lower pressures and didn't leak out or require junk components that transfer heat better just thinner and unserviceable.

Stinks, but may need something stupid that isn't even A/C and have to discharge it to do other work off season so not knowing would be a real pest.

It's extra nice when it's naturally warm enough outdoors to need A/C so you really know how they are performing.

****************************

Did ONE (last time for that) when 0F and windy outside! Another shop's job all fixed just a broken part like a condenser - a rock went thru it or something. Customer wants it working upon arrival in Florida in a few more days expecting 80s and humid so I try.

First issue is I don't heat all the product or equipment so bring all that inside and heat shop with that car to 100F for hours. Charged to spec and need to know now if it will blow cool air as designed. What a PITA. Put heat on in car in shop and quick switch to A/C and take observations and it worked but only had seconds to see it. Had to open shop door so the blast of ARCTIC came right in and ended testing.

Just did hear it worked fine later that's all. Never again. It took me mega hours to do that,

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Re: R134a conversion - problem, or unrealistic expecations?

Postby foamypirate » Mon Jul 25, 2016 3:29 am

Cooling seems to have gone downhill a bit now. 60F after a 1 hour drive at 70mph...granted, it was 98F or so out, but should be plenty of time to cool the cab down to be able to blow below 60F. On Friday on the ~15 minute drive home from work, same conditions, it hit 54F. Cab is sealed up tight. Maybe I went backwards pulling the 2 oz of refrigerant out?

Getting to the point of frustration. For the money I've invested, I feel like this thing can cool much better than it is, I'm just not sure what to do now without spending a bunch of money. It's costing me $75/pop to mess with the charge.
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