Main IndexAuto Repair Home Search Posts SEARCH
POSTS
Who's Online WHO'S
ONLINE
Log in LOG
IN







Search Auto Parts

R134a conversion - problem, or unrealistic expectations?


  Email This Post



foamypirate
Novice

Jul 22, 2016, 2:24 PM

Post #1 of 15 (589 views)
R134a conversion - problem, or unrealistic expectations? Sign In

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/ 60% 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.


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jul 22, 2016, 3:40 PM

Post #2 of 15 (583 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

If you were to somehow unseat the orifice reversing blowing, you would think the pressures would be equal and low. Pressures are getting too high if your tripping the HPCO switch. Seems the heat just can't get off the compressor for some reason. Add that to 93F and also with a big ole crew cab to cool down. Is the weatherstripping in good shape? Cabin kind of sealed good? Does the recir door work. Being that old you can expect the foam on the doors in the chamber box to be disintegrated possibly allowing heater core air to mix in? Can you hang your gauges out the hood and drive the vehicle on the highway to see what kind of pressures you are getting? I'm sure the compressor is busting its ass trying to move the heat.

The old system held around 2.8 lbs r12 with the old R4 compressor? Wonder how they figured out how much refrigerant to put in with the different compressor and hose arrangement? Believe it or not it is possible that it could be overcharged with 2 lbs of R134.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 22, 2016, 5:49 PM

Post #3 of 15 (575 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Sure seems like you have either not enough condenser or too much refrigerant.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



foamypirate
Novice

Jul 23, 2016, 6:26 AM

Post #4 of 15 (563 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Thanks for the input, guys! I'll see if I can have a few ounces taken out of the charge and see what happens. Also beginning to wonder, based on another suggestion I saw, that the A/C shop may have added more oil before they charged. I already had a full 8 oz in there before I took it in.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 23, 2016, 6:53 AM

Post #5 of 15 (560 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Find out on oil. A couple wouldn't change much IMO.


Keep as exact track of the weight of the charge as possible. Weigh what you remove ounce by ounce and take it for a spin around the block and see how it does.


Again - this has the symptom's of either (either one) overcharge or inadequate condenser performance for any reason or pressures would spike that high,


T



Prospector
New User

Jul 24, 2016, 9:00 AM

Post #6 of 15 (534 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Do modern auto ac systems still use a sight glass? I am a certified type 1 and type two refrigeration mechanic but do not do much auto ac. Those sight glasses were quite handy when you wanted to charge an ac system. Is it safe to assume that your system does not have a sught glass?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 24, 2016, 9:18 AM

Post #7 of 15 (533 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Sight glasses were on used in expansion valve type systems only and never on orifice tube systems. They are pretty much eliminated in late model systems. When doing a 134 retrofit, they are completely useless because the systems are intentionally undercharged and will always show bubbles.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



foamypirate
Novice

Jul 25, 2016, 2:41 PM

Post #8 of 15 (498 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Well, I tried tweaking the charge a few oz. in both directions without much change. Took an extended (1 hour) drive to visit a friend, and the lowest vent temp I saw on the trip was 60F. On the drive home in the dark, it did hit 48F or so. Average vent temp now seems to be 60F with 100F ambient and 40% humidity. I did add some foam insulation around the radiator and condenser to direct as much airflow as possible through the condenser and radiator. Didn't seem to help much.

Next test will be to block off the heater hoses and see if the vent temp improves any. I'm also thinking about having the charge recovered and swapping to a GM .072 white orifice tube. I'm beginning to wonder if the blue tube is artificially driving up my high side, and preventing the evaporator from getting enough refrigerant. Not sure though.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 25, 2016, 2:45 PM

Post #9 of 15 (496 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Yes, that really should have a white tube.

After you get it recharged and running, feel the temp of the liquid line at idle and see if it is warm to the touch or hot to the touch



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



foamypirate
Novice

Jul 26, 2016, 5:10 PM

Post #10 of 15 (478 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Haven't yet had a chance to change the o-tube out.

Today, we had a nice storm blow through, and the temp dropped to about 82F and 80% humidity.

Not sure if this is relevant or helpful to determine charge, but when I had the truck running in the driveway, engine fans full bore, doors open, and the interior fan turned to the lowest setting, the accumulator was literally so cold I couldn't keep my hand on it for a long duration. Even the rubber hose back to the compressor (about 1/2 of it, anyway) was sweating (though the humidity was quite high).

Does this indicate an overcharge? I'm afraid if temps drop any lower, if I end up running the fan on slow speed, I'll slug the compressor with liquid refrigeran. Or am I just seriously overthinking this?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 26, 2016, 5:13 PM

Post #11 of 15 (474 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

You can't check a system that way.

Doors closed
high blower
max AC
measure center vent



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



foamypirate
Novice

Jul 26, 2016, 5:26 PM

Post #12 of 15 (472 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

10-4. It was more of an experiment than anything. I hadn't really tried the lower fan speed settings.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 26, 2016, 5:28 PM

Post #13 of 15 (468 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

That will cause anything to get cold.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



foamypirate
Novice

Jul 27, 2016, 9:41 PM

Post #14 of 15 (441 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

Made a lot of progress today. We dropped the charge down to 26 oz, and things are WAAAY better. 90F, and even after extended idling, the high side was around 280-290 (still a bit higher than I'd like, but certainly better than 350-375). The HPCO no longer trips, even with about 1,500-1,800 RPM. The low side was 44-45. With the fan on max, and going down the road, I saw the vent temp dipping into the 46-48 degree range. Turning the fan speed down one notch resulted in 42 degree temps, and the clutch started to cycle. Once I finished my test loop, I popped the hood, and the whole accumulator was sweating, along with about 1 foot of rubber hose on the suction line off the accumulator. I think the charge is pretty much right on now. I might play with dropping the low pressure cut out just 1 or 2 psi to get that last little bit of cooling, being careful not to ice the evaporator, of course, but overall, MUCH happier with the system! I'm blown away by how small the charge is. I guess that PF condenser compared to the giant factory dual tube serpentine, and my shorter than factory hoses made quite a difference in system volume.

Thanks again for all the help and input!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 28, 2016, 4:14 AM

Post #15 of 15 (432 views)
Re: R134a conversion - problem, or unrealistic expectations? Sign In

I think you are still a bit overcharged.

This was one of the first responses you received.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







  Email This Post
 
 


Feed Button




Search for (options) Privacy Sitemap

shopify
site analytics