Excursion A/C issues, HELP

Moderators: Nacho, Tom Greenleaf, ACProf, acsource

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Sat Aug 29, 2015 4:02 am

an over abundance of oil in the system will impede the transfer of heat from the aluminum to the Freon, so you might be onto something there, but I would expect to see lower low side pressures, as the Freon would be much colder then the air passing thru the evaporator core.
Is the suction line at the compressor cold? how about the compressor body itself?
I am loath to recommend "throwing parts" at the problem, but if pressed, I would take a hard look at the accumulator and return line to the compressor. lets say for example, a piece of styrfoam packing ( or aluminum welding slag) got lodged in the accumulator and partially blocked the outlet, that would give higher low side temps, and pressures and not cycle the clutch, as the switch is before this restriction, so it always "sees" the higher (50 psi) pressure, while the compressor inlet "sees' much lower pressure and temp. You might not even be able to detect it by "blowing thru" the accumulator on the bench.
Also take a hard look at the outlet temp from the CONDENSOR, if the Freon can't dump its heat load, it just recycles back to the evaporator. The outlet tube on the condenser should only be 10-20 deg warmer then the air passing thru it with normal air flow thru the condenser. Even at 90 degs with both front and sleeper air running, the outlet of the condenser on my truck is only slightly warmer then the air. It only has a 18,500 BTU condenser and two evaporaters with 1.5 ton Tx valves. On my the other truck I have the room for a 31,000 BTU condenser and it has no problems what so ever. The extra capacity acts like a receiver for liquid freon.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Sat Aug 29, 2015 8:09 am

I did check the condenser outlet tube earlier and it was pretty warm, I will use an IR gun to see if I can get a good temp reading on it. If I had to guess it would be about 20-30 degrees warmer than the outside temperatures. I checked right when I started the ac system and it was very hot but it slowly cooled down to the 20-30 above.
The suction line is very cold coming from the accumulator and yes the compressor body is also pretty cold. Both are covered in condensation within a minute of turning the ac on. I will remove the accumulator and look for any issues and then replace it while it's apart.
I am also looking for a tool that I can use to cut open an accumulator to inspect. Any ideas? I didn't want to use a Sawzall because I want to look for metal in it that I didn't introduce.
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby Cusser » Sat Aug 29, 2015 2:24 pm

Is the accumulator cylindrical? If so, try a loaner tailpipe/exhaust cutter loaner tool, works like a big can opener.
User avatar
Cusser
 
Posts: 494
Joined: Wed Jun 29, 2005 4:22 am

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Sat Aug 29, 2015 2:30 pm

If you had a big enough pipe cutter, that would open it up without putting any metal inside it.
how is the airflow over the condesnsor? On trucks we have an air operated clutch so we can know the fan is on and really moveing air over the condenser, with a viscous clutch it can be harder to tell if it is moveing as much air as it can or slipping, as they always slip a bit.
Really cold return line and cold compressor body (colder then evaporator, or vent temp) sounds like there must be a restriction "starving" the compressor. Remember, if Freon can't get back to the compressor, neither can the oil! This may be why you seeing it in the evaporator when you changed the Tx valve.
I think what is happening, is the system quickly pumps all the Freon to the high side (showing as high condenser temp), then moves very little Freon as the suction side is starved. The low side tap is before what ever is restricting the return, so it "sees" 50 psi or so, the compressor stays on because the low pressure switch is also before the restriction. My guess is if you could put a low pressure gauge right on the compressor, you would see damn near a vacuum on the suction port. Because the rear air isn't cold, the restriction has to be after where the return from the rear ties into the return from the front, at or just before the accumulator? I don't know how these systems are plumbed.
If I am correct in my theory and this system has been run this way, there may be compressor wear from lack of oil returning, but that would be fairly easy to tell once the system is working properly.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Fri Sep 04, 2015 2:40 pm

I was looking at a cut-a-way of a accumulator on automotive A/C system.... There was the answer to your problem, I think.
The inlet from the evaporator stops near the top. The return to the compressor is a U shaped tube, this is so any liquid Freon will not be drawn back to the compressor, only vapor from the top of the accumulator. There is a small hole in the bottom of the U tube to draw in any oil that is on the bottom of the accumulator. I think the main opening of the U tube is clogged, and it is drawing only thru the "aspirator" hole for the oil. Like adding a 2nd orifice tube at the bottom of the accumulator.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Sun Sep 06, 2015 9:51 am

I decided to dive into replacing the front evaporator, accumulator and condenser (since its not flushable). Everything in the system is new except for the front evaporator. The front evaporator wasnt as clean as I had originally thought. Last time I inspected it I removed the blower motor and used a mirror and I thought it looked decent. Bear with me because this story will bounce around a bit.

My evacuation machine process is that it recovers the refrigerant and when there is no pressure in the system it will pull a vacuum down to 10" and hold it for 2 minutes to check for off gassing. If off gassing occurs the gauges reflect that and it will continue to recover and once it hits 10" vacuum it will start the 2 minute timer over again. This process goes until 10" of vacuum is held with no off gassing for 2 minutes. My Excursion is the only vehicle I have ever seen that has off gassing (because its dual air system??) so it takes a while longer to evacuate the system completely. Even after the machine has said recovery is complete and the gauges show 10" vacuum, I can opt to recover again and it will usually recover 6 to 8 ounces on the first try and then maybe 1 ounce the next 1 or 2 tries. I dont believe its a fault in the machine because the gauges show a steady and holding vacuum, but once I start to recover again the gauges will usually go up to about 10 psi and slowly drop to 10" vacuum. I was discouraged because I thought something was wrong with my machine until this next experience.

So after recovery I jumped into removing parts to get the front evaporator out. I opened up the orifice tube joint and removed the orifice tube, removed the line from the top of the accumulator that goes to the compressor and then I had to go to my toolbox to get larger wrenches to open the connection that goes from the front evaporator outlet to the accumulator. As soon as I barely touched that connection with a wrench, hadnt even got the wrench into position, a blast of air comes out of the top of the accumulator where the connection is open for the line that goes to the compressor. It was a strong enough blast that it splattered pag oil on the bottom of my hood. The only thing that I can think of to cause this is there is a restriction of some kind in the evaporator that was holding pressure or something similar in the accumulator. I will cut the accumulator open and take pictures and also blow out the evaporator and take note of what comes out. Until then I am waiting on parts before I flush the entire system. I will try to attach pictures, hope this works.

This is the front evaporator. If I had known it was this dirty I would have replaced it a long time ago. But this issue isnt causing my low side pressures to be high correct? Hoping its a flaw in one of the components and all will be well after the rebuild.
Image



This is a sketch of how the Excursion system is set up. Another picture is attached lower that you can see the connection that requires larger wrenches.
Image

I took this picture right after the air and oil blasted out of the accumulator port that is open.
Image

Image
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby GM Tech » Sun Sep 06, 2015 1:38 pm

I would not hang my hat on a restriction -- burping/belching after lines are removed from an accumulator is very common- the refrigerant is "trapped" in the oil in the accumulator and is ice cold- as can be felt and seen by the sweating when you extracted the refrigerant. The trapped liquid refrigerant "explodes" when it warms to the point of expansion- and blows the oil out- unfortunately after you unhooked the lines and now have an oil soake, dye soaked engine compartment. To avoid this, you must always apply heat to the accumulator as you extract the refrigerant with your recovery machine- use of a hair dryer is the best way. Another way is to run the blower motor- putting warm air across it, because the evaporator is also cold- and needs to have the refrigerant "chased" out of it as well. Upon recovery, if any a/c element is cold, you still have liquid refrigerant trapped in it- especially in any oil pools- so next extraction look/feel for all the cold spots and apply heat accordingly to get all the refrigerant out BEFORE you open any lines. The a/d and evap are the most common oil/refrigerant pools.
'95 Chevy 3500 454 Dually 142,000 miles
'94 Chevy Astro Van 358,000 miles!
'86 Buick Park Ave 192,000 miles
'86 GMC S-15 Pick-up 150,000 miles
'92 Chevy Lumina Van - 265,000 miles- given to me to see how far it can go! all above are white!
User avatar
GM Tech
 
Posts: 1130
Joined: Tue Jun 28, 2005 12:23 pm
Location: Dayton Oh

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Sun Sep 06, 2015 3:23 pm

I'm more hopeful then GM. Lets take a look at this with all the info you have posted so far, with the locations of the low side tap and cycleing switch. Both these items are on the accumulator, both have indicated aprox 50 psi (gauge read and high enough not to cycle the clutch). However, you did notice ice on the outside of the accumulator. For that to happen there has to be some sort of restriction in the accumulator.
Was the system run right before you vacuumed it? If not there is no reason for ice to form anywhere as the pressure should be equal everywhere in the system.
Next lets assume that liquid refrigerant is trapped in the oil, and the vacuum is pulled at the low pressure port, that indicates a blockage between the low pressure port and the oil in the bottom of the accumulator. Since the return line was off the accumulator (line to the compressor) there must be something still holding the liquid oil from releasing the refrigerant (must be under enough pressure,or be too cool to vaporize). If the system wasn't run beforehand, that leaves either the evacuating equipment can pull the refrigerant out so fast that it can cool to iceing point (not likely thru normal charging hoses) or there is some restriction acting like an orifice tube causing a choke point. Unless accumulators used on dual systems have a check valve in the outlet (possible, to prevent returning refrigerant from the rear, raising the pressure in the accumulator, and reducing the fronts cooling and causing short cycle times of the compressor) the accumulator should have been at atmospheric pressure, even if had a blockage, both tube were open to air. One via the orifice tube connection, the other at the return hose connection. Again, I have little experience with CCOT systems as I own only one, and other stuff I work on has Tx valves. Check valves are common on commercial refrigeration equipment with multi evaporators esp if they operate at different temps. They prevent the warmest evaporator from "back feeding" the cooler ones.
I still think the accumulator is the problem. Even on trucks with dual air, you don't see the vacuum rise. If you open both low and high valves when you pull the vacuum, it falls steadly and holds a low vacuum if there are no leaks. With yours rising it suggests either a leak or a pool of refrigerant that is boiling and slowly making its way to the port thru a restriction.
The dirty evaporator will reduce the cooling, but would not cause the problem. The dirt will reduce the heat transfer the refrigerant would exit the evaporator at a lower temp (and therefor pressure) then if there was good heat transfer. You pressure measured at the accumulator was correct for the vent temp measured. That says that the transfer was good enough to boil the refrigerant. Obviously you want to clean it, but it wasn't the cause of the problem you are having.
I would change the accumulator and clean or replace the evaporator, then triple vacuum the system, and recharge.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Sun Sep 06, 2015 3:40 pm

also if the rubber part of line "A" is long and straight enough, I would cut and splice in a section of tube with another low pressure port on it. This way you could monitor the low pressure at the inlet of the compressor as well as at the accumulator.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Sun Sep 06, 2015 6:15 pm

Thank you for the info guys. I'll see if the local ac shop can put a low pressure port in that rubber line but it is a short line and already has a decent bend in it. May not be able to. I'll try to cut the accumulator open today and take pictures.
Is it possible that something in the compressor could cause it to produce adequate high pressures but not pull enough do drop the low side?
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Sun Sep 06, 2015 6:26 pm

If you can find a shop that can weld aluminum, they should be able to weld a port into the aluminum section of that line. I just suggested splicing as many have access to hose crimpers but not aluminum welding. It would be a nice diagnostic tool if replacing the accumulator doesn't solve it.
The more I think about it, the more likely there is a check valve in the accumulator outlet. Otherwise when the compressor cycled off, the accumulator pressure (and front evaporator temp) would quickly rise with the returning rear refrigerant. The front evaporator being more sensitive to accumulator pressure/temp with the fixed orifice tube then the rear with Tx valve. Otherwise, why not return to the accumulator inlet? But I must admit I am guessing here as I never worked on a vehicle of your type. I just know that commercial systems use check valves to prevent warming of the cooler evaporator when the compressor shuts down on multi-evaporator systems.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Sun Sep 06, 2015 6:40 pm

This system is not like an air compressor pumping into a closed tank, it is much more akin to an engine oil system, where pressure is determined by restriction of the flow, and everything eventually returns to the inlet of the pump. for the compressor to be able to achieve high pressure, it must be able to move low to high. I don't think anything is wrong with the compressor at this point.
For the compressor to be at fault, just think if you had too small a displacement (or turning too slow) the high side would be low and the low side high. This is sometimes seen on a compressor with one (or more) broken reed valves.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Tue Sep 08, 2015 10:52 am

I finally had some time to open up the accumulator. Everything looked as I thought it would except for a pinhole thats up high on the suction tube going to the compressor (pictures attached). I blew out the fins on the evap and it definitely was in poor shape but I dont believe that either of these will fix my problem. Please correct me if Im wrong but with a properly operating evaporator vs one that is in poor flow condition, wont the system show higher low side pressures with an evap that has good flow? I also blew out the evaporator and not much oil came out of it, maybe a half ounce. There was about 2 ounces in the accumulator.

This is after cutting open. This is the desiccant bag zip tied to the tube in the bottom of the accumulator.
Image

Zip tie removed, can see the screen "filter"
Image

Desiccant bag removed and filter slid away to reveal the pin hole in the bottom of the tube that sits in the bottom of the accumulator
Image

This part I did find interesting and maybe this is the reason the suction hose was cold and also the compressor. There is a small pinhole up high in the accumulator on the suction side. My dad also had a good question after having a look, why is the suction line all dinged up? Looks like something has been putting small dings all over the higher portion of the line.
Image
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Tue Sep 08, 2015 11:12 am

I also forgot to mention that when I started to take the system apart I was smelling something that wasnt pag oil or refrigerant. I then remembered what the smell was, I used a flush solvent that I purchased from a local parts store that had a unique smell. It didnt smell like any chemicals but rather like an organic solvent. Its not very thin like a solvent either so maybe there was an abundance of this stuff left in the system that did not get removed when I was blowing it out with air after I used the flush.
Image
Image

I dont know if I had mentioned this in the post already but I did fall for the DuraCool AC Oil Chill hype and that is what I used in this system rather than pag 46. Anyone have knowledge good or bad on this product? It is half way down this page. The local AC supply house sells this stuff and I thought I would try it out.
http://www.duracool.com/Duracool/acsolutions.html
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby GM Tech » Tue Sep 08, 2015 1:46 pm

GM had a policy- NEVER flush with a solvent-- because you can never get it all out-- so I never do, if anything I use a flushing adapter on my recovery machine and use liquid refrigerant to flush with.....now you know why. Dealers still flushed with the over-the-counter solvents and warranty returns with nasty stinky compressors soared. Some even used laquer thinner (cheaper they said) or even brake cleaner! So if you have solvent residue in your system, it may well be what is causing your bad pressures and cooling. Never put something in your system you can't get out. Blowing air through an evaporator is worthless- there are parallel paths that can't be cleaned out- same with condenser, unless serpentine type.

The pin hole at top of accumulator tube is the anti-siphon hole - sometimes referred to as the pressure equalization hole- keeps liquid refrigerant out of the compressor to avoid compressor slugging after a cool all-night sit.
'95 Chevy 3500 454 Dually 142,000 miles
'94 Chevy Astro Van 358,000 miles!
'86 Buick Park Ave 192,000 miles
'86 GMC S-15 Pick-up 150,000 miles
'92 Chevy Lumina Van - 265,000 miles- given to me to see how far it can go! all above are white!
User avatar
GM Tech
 
Posts: 1130
Joined: Tue Jun 28, 2005 12:23 pm
Location: Dayton Oh

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Tue Sep 08, 2015 2:33 pm

The pin hole at the bottom is to draw in any oil at the bottom of the accumulator, so it will return to the compressor.
As to the evaporator, if it can't absorb heat (dirty externally) the refrigerant will exit at a lower temp and pressure then if it absorbed heat, so the accumulator pressure would be low. If the evaporator was restricted internally, outlet pressure would also be low, but the inlet higher.
anything to indicate a restriction in the U tube? Look close at the return tube to the compressor. IS it possible that the return line from the rear was inserted too far into the return line before welding and forming a choke point? If no on both then I think it is extra important to get a low side tap as close to the compressor as possible for diagnosing purposes.
On the upper part of the U tube, if they are pits, I would guess moisture corrosion, if they are just dimples, then it may be made by the forming machine making the U tube.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby cornbinder89 » Fri Sep 18, 2015 6:32 pm

Any luck with this? I would like to know how it turns out.
cornbinder89
 
Posts: 212
Joined: Sun Mar 22, 2015 9:10 pm
Location: Lyman, IA
Favorite Refrigerant: R134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Fri Sep 18, 2015 6:49 pm

I just received the last 2 pieces for the rebuild (the foam seal around the front evap and the reflective heat barrier for the evap cover under the hood). I have roofers here today and painters here tomorrow and I don't like advertising my tools so I may not be able to get started on the rebuild until Sunday. I will take good notes and post my results.

I did run a wire through the U tube in the old accumulator and it did not have a restriction. I will check the rear tube into the return like you mentioned today to see how that looks. Thanks again
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Thu Oct 01, 2015 12:55 am

So I finally had some time to start on cleaning and rebuilding the system. I am not getting much oil out of the system so far and its kind of strange. I know that I installed 14 ounces of duracool oil on the last rebuild, I wont use that again. I also used FJC A/C flush and I wont use that again. Ive been reading that this brand of flush leaves a residue in the system and I believe it does since I can strongly smell it in the components when I take them apart to clean, it smells like peanut butter.
PAG (Duracool oil I should say) oil removed so far:
Compressor- Maybe 1/4 ounce
Accumulator - Maybe an ounce
Front evap - 1/4 ounce or less when using compressed air
Hoses - 1/4 ounce or less
Condenser and rear evap - Haven't tried to blow them out
Lines to the rear - Have not blown out yet

System requires 14 ounces so somewhere there's some pooling going on. On the last few recovery's with my machine I have not been getting any oil which is also odd. Which brings me to my next question, if the system requires 14 ounces, where and how much should I distribute the oil?
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

Re: Excursion A/C issues, HELP

Postby Daves Garage » Fri Oct 16, 2015 5:00 am

Finished the job today and seems to be much much better. I Installed everything new except for the compressor and hoses. I tracked down some double end cap PAG 46 oil and installed 7 ounces in the compressor, 6 in the condenser and 1 ounce in the accumulator. I compressed the system with nitrogen up to 200 psi and I didnt hear any leaks so I dropped it to 150 psi and let it set for 24 hours, stayed at 150 psi. I vacuumed for 1 hour and it got down to 320 microns. Dropped to 450 microns within a few minutes of starting vacuum. I charged the 4 lbs 4 oz and then spun the compressor over several times by hand to move the oil. I idled it up to 1300 rpm approx. and then the front vent temp was 40F and rear vent temps were also 40F. Engine temp wasnt even warmed up completely so it may get better while moving down the road. Pressures were 44 Low 175 High while idling at 7 or 800 rpm. I turned the rear air off and the front vent temps dropped to mid 30's. Pressures with just the front ac were 30/170 while idling at 7 or 800 rpm. It was an ambient temp of about 88F and the sun was going down so I hope it works this well during the day with warmer temps. I will report back.
User avatar
Daves Garage
 
Posts: 26
Joined: Sun Aug 09, 2015 7:24 am
Favorite Refrigerant: 134a

PreviousNext

Return to A/C Questions and Opinions

Who is online

Users browsing this forum: Bing [Bot], The Google [Bot] and 11 guests