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very high low side pressure


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me2amjw
Novice

Aug 29, 2014, 4:43 AM

Post #1 of 12 (2194 views)
very high low side pressure Sign In

After evacuating my system, when I try to charge it I'm getting extremely high low side pressures and lower than normal high side. Now I know most are gonna be thinking bad compressor, but this is a brand new compressor and the same thing was happening with my old compressor, which is why I installed a new one. As I'm charging, the low side keeps climbing and gets over 100 before I even get the required amount of refrigerant in. The high side didn't get over 100.
Before these strange pressures started I made a modification to the liquid line. The orifice tube was originally in the outlet stub of the condenser, which I thought was really stupid, so I bought a compression device for containing an orifice tube and straightened a very contorted liquid line and put the orifice tube just before the evaporator. I used a different color orifice tube in this gadget than the original. I don't recall why I did that. Anyway I'm wondering if this mod could somehow be causing the pressure problem.
While I had the system apart I flushed the condenser and the lines but did not flush the evaporator because I cut the old accumulator apart and didn't find any unusual crud in it. I have searched for info on how incorrect orifice tubes affect pressures but couldn't find anything definitive. Does anyone know for sure whether this mod can be causing such weird pressures?


Discretesignals
Ultimate Carjunky / Moderator
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Aug 29, 2014, 4:50 AM

Post #2 of 12 (2192 views)
Re: very high low side pressure Sign In

More than likely yes. What is the year, make, model, and engine size? Don't understand why you would reenginner something like that. If the manufacture thought it would be better to place the orifice near the evaporator, don't you think they would have done that? If you put it back to how it was originally, how does the systems operate and the pressures look?





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Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 29, 2014, 5:04 AM

Post #3 of 12 (2187 views)
Re: very high low side pressure Sign In

Same as DS - What year, make and model. Why the changes in "O" tube and what happened to original compressor? You pretty much can't flush out a condenser but it sure could catch some kinds of junk. If refrigerant flows past things for any reason too fast you will see high low side pressure but you've altered it and I say put it back first before you blow this compressor too,


T



Hammer Time
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Aug 29, 2014, 5:16 AM

Post #4 of 12 (2181 views)
Re: very high low side pressure Sign In

Different color tube represent different size orifices and will effect cooling but now what you are experiencing.

If you are getting a high low side and a low high side, the compressor is you only suspect. Don't assume it's good because it's not old.



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me2amjw
Novice

Aug 29, 2014, 8:59 AM

Post #5 of 12 (2160 views)
Re: very high low side pressure Sign In

My pickup is a 94 Dakota, 3.9 and I certainly don't think manufacturers always use the best designs. Having the orifice tube right at the exit of the condenser means the refrigerant is expanding and picking up heat from the engine compartment for about four feet before it begins to do any cooling of the cabin. And the old compressor apparently didn't go bad; I just thought it had because I was getting those weird pressures and all the research I did kept saying it had to be a bad compressor. Since a brand new compressor is giving me the same grief I now think it is highly unlikely to be, or have been, the compressor. One thing sure is that I'm not going to buy another new compressor until I know for certain that is my problem. I do plan to put the orifice tube back where it was and see what effect that has. At least that shouldn't be terribly expensive.


Tom Greenleaf
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Aug 29, 2014, 9:17 AM

Post #6 of 12 (2159 views)
Re: very high low side pressure Sign In

! What was the performance at the vents for this thing before you decided to re-engineer it? Any makes does some dumb stuff. Tube on suction side being too close to engine heat really shouldn't be an issue really yet I've seen some near touching glowing exhaust parts (other vehicle so forget it) and mattered.


Model year 1994 was first full year to use only 134a. Can't know each maker but many just retrofitted all old components rather than a complete redo of HE stuff like condensers and evaps and replacements now may indicated to lower refrigerant capacity for OE, parts fit but may look a bit different and lighter. They worked fine especially in a pick-up with no area to cool anyway.


So, was it working before you did all this that hasn't changed anything yet? Now perhaps all messed up with air possible even if by mistake?


Sure your reading are correct? Tossed a compressor on a guess and change color and location of "O" tube-------------- I've said enough,


T



Hammer Time
Ultimate Carjunky / Moderator
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Aug 29, 2014, 10:20 AM

Post #7 of 12 (2152 views)
Re: very high low side pressure Sign In


Quote
and I certainly don't think manufacturers always use the best designs.


Really? Where did you get your engineering degree?



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me2amjw
Novice

Aug 30, 2014, 9:17 PM

Post #8 of 12 (2131 views)
Re: very high low side pressure Sign In

Hammertime, you are an exceptionally arrogant and condescending person to be pretending to give helpful advice. Where did you get the idea that anyone must have an engineering degree in order to have any knowledge of a subject or to have an opinion? I don't pretend to be an expert at air conditioning, or at anything, but I have been doing all my own auto AC work for over 40 years and this is the first time that I have been totally unable to solve a problem. Does that make me an idiot in your view? It seems to me all you people would much rather criticize that give any constructive advice. All of you just forget my request for help. I don't need that kind of "help".


Tom Greenleaf
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Aug 31, 2014, 2:41 AM

Post #9 of 12 (2128 views)
Re: very high low side pressure Sign In

Refresh this: Put system and "O" tube back to OE. High low pressure/suction this thing is just making a pointless loop right now.


* Condensers don't flush at all or well and at best if HE must be laid flat for a chance but could work partly if plugged with something hard you wouldn't know without destroying old one for sure taking off end tank/in area to see it. Not worth the trouble. Toss them when too old or been worked on too much just anyway.


* What was the performance temperature wise at the center vent before you touched it and the pressures? A CCOT set up should tell you pretty easily how well it's working with pressures, touch and feel or IR thermo checks.


** It will remain #1 till hell freezes over before the most common reason for poor performance didn't originate from a low charge, lack of oiling and continued use bring on the failures IMO.


Mopars have an unusually high record of failed leaking evaporators<> most any a royal pest to replace and fit isn't always so great. One would think trucks would have more available longer in general longer than cars.


When you can take observations with all knowns to spec and charge to spec by an ounce or so then you can make a clearer diagnosis if not performing up to par.


At age factor dirty things even ducts and items in HVAC box that don't belong, debris of any type up to damage from critter nests or who knows what junk.


Another is if system has had sealers or non OE magic tricks attempted over the years or ever it could be a permanent problem till totally cleared out or items replaced.


<> = Most people with an older vehicle might try so called metal sealers when they find out the effort costs for an evap and give up when that fails and no telling what lingering problems would happen from assorted types but many are sold.


You also need to trust your equipment and gauges. Even quick connects and hoses give up or NG new sometimes......


T



me2amjw
Novice

Aug 31, 2014, 6:30 AM

Post #10 of 12 (2122 views)
Re: very high low side pressure Sign In

Thanks Tom, for some advice without criticism. I don't know what the vent temp was before my tinkering because I didn't use a thermometer on it. I could just tell by feel it was not as cool as it had been. I had a slow leak for a long timeā”€one can every other year. I have an electronic leak detector and once I injected UV dye, but still couldn't find the leak. My plan now is to put the O-tube back to original position and see what effect that has. If it's still not satisfactory, I plan to replace the condenser.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 31, 2014, 7:20 AM

Post #11 of 12 (2119 views)
Re: very high low side pressure Sign In

OK - Let's fix this thing. I show OE charge as 32oz from full vacuum which can be wrong so look for under hood info for what it is or was OE.


By cans you mean the 12oz I take it? Most are. Use pure only or this crap could be full of junk you don't want ever.


Thermos: My own most fav is the cheap wired household ones! With those you can watch center vent temps while being under the hood and another ($10 buck things) out in front of condenser which is the temp the A/C is dealing with. Switch those cheap things to in/out settings and you have info quick and easy. Everything about A/C is temp and pressures + when and where it's a liquid or gas so need that to know.


IR thermo: Go wild or not but handy if not windy. Radio Shack or other about $20 + a battery is pretty good. Key fob size thing. Just used one this second and my body temp shows I'm alive! If you'd like a sode my ice is 10.5F right now in fridge behind me. Cool thing pun intended. This can go whacko and useless too. This thing also streams along such that you can follow a line on anything solid (not good in air) and just streamed outside of my fridge metal which is within 2F of ambient so isn't losing much cool to room - good. Didn't vary much from freezer side to regular side. Handy freaking diag tool.


For vehicles going along a line that should be similar if it showed a sudden change locates a blockage. Condenser not so great at.


So back to adding or boosting as you said. I take it you mean 6oz every other year is 3oz/yr so kinda slow to show itself. Sorry, I'm known for being verbos but have to do some guessing not being there and ask. So these 12oz cans you leave the tap or tap and hose on probably? Weigh them with an accurate postage scale - full can by brand and lot as they don't all weight the same tare weight even if they didn't lie that 12oz is the actual contents. Add for your tap and hose if you leave it on and just do math. Purge air out of even tiny hose if that type - just a quick spit but not enough to show loss of refrigerant weight. Put finger over end so no air can get in as that tiny bit time after time will mess up readings which are for pure refrigerant. Air both has moisture and isn't condensable so all bets off and worse with PAG oils any moisture makes it acidic which can rot thru system parts - don't want that of course.


Can't know what stuff you have or made up. I do use little cans (bought cases of it for a buck a can) and can run thru top end gauge set and do either 134a or R-12 and still have one of those OE working fine and plenty of virgin R-12 but cans are old now and those you can't keep/save if you use partial can with those taps or never could. Will not open last 30lb sealed bottle unless absolutely anal about keeping something R-12 which isn't necessary for me personally.


So you need a few bucks of stuff and what I do is keep one wired remote thermo in center vent so I know if it's not up to snuff and another for accurate outside incoming air only good while moving so I don't wreck a compressor if it does leak too low to keep it lubed and shut it down on time.


In short I think you need a new condenser just because and it may be working but most new unless defective should be total plus for this truck if you really want A/C to last for some good time. Surprises happen new or old like where I am a rock or shat from roads bang right into condensers and seem to like new ones not the old ones dammitMad


So the summary is to get this back to OE. The makers do make some stupid moves but this vehicle is not on that short list. When charge is known and all temps pressures known then if just that doesn't fix the thing you can make a credible diagnosis. Try to keep track of what you've done and added for oil which IMO can be off some but unless flushed clean you don't know how much is in it and too much makes things act up and too little will wreck compressors.


Remember you can fake it with higher capacity systems and this is already low at just 32oz. The newer the less required so knowing weight ever more important and needed for a baseline when problems come up. Post long enough so taking out signature........ T


Hammer Time
Ultimate Carjunky / Moderator
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Aug 31, 2014, 7:34 AM

Post #12 of 12 (2115 views)
Re: very high low side pressure Sign In


Quote
Where did you get the idea that anyone must have an engineering degree in order to have any knowledge of a subject or to have an opinion?


Well, you are stating that the people that actually are engineers don't know how to design a refrigeration system. What qualifies you to say that?

There's a difference of opinion on who is the arrogant one here.



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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.







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