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Low side normal /high side low stumped
Posted: Tue Jun 22, 2021 6:30 pm
by Excursion2001
New to the forum guys don’t know a whole lot about ac just started getting into it . The guys on my diesel forum don’t have a lot of use when it comes to this and neither do I . So I have a 2001 Ford excursion front and rear ac . Iv have replaced the entire ac system due to the fact it did not have a ac compressor on it and it was left opened for over a year from the previous owner . I put all the new parts on oiled and vacuumed down . Checked for leaks zero . Charged it and gave it the desired amount (68oz ) of freon . And I noticed when I was charging it the high side was about 100psi under where it should be . For the outside temperature I was getting roughly 112 degrees my low side was 3.8 bar (55psi) and the high side was 16 bar (232psi) im supposed to be at 350ish based on temp outside. No matter if im at idle or driving down the road it only blows out 70-75 degrees out of the vents would could cause this ? Iv trying looking it up and I haven’t found a whole lot to my problem any help would be great ! By the way I have a txv in the rear ac and a orfice tube in the front . I was told when putting together this unit that if I used this different orfice tube it was supposed to make the ac colder idk if that has anything to do with that or not
Re: Low side normal /high side low stumped
Posted: Tue Jun 22, 2021 9:13 pm
by tbirdtbird
Need more info.
" I'm supposed to be at 350ish based on temp outside". That is kinda high, what is your ambient?
Did you change the dryer
Did you drain out the oil that came in the compressor, measure, and put in new of the correct amount and kind
What equipment did you use to pull a vacuum? The 'pumps' that run off compressed air will not get you low enough
How did you determine you pulled sufficient vacuum? Vacuum gauge? A system open that long is gonna need a lot of evacuation
Did the old compressor grenade? There is a reason there was no comp at all. If so the system is contaminated with the black goo of death.
How did you check for leaks
ETC.
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 7:18 am
by JohnHere
As mentioned previously, I think we need more information to diagnose this.
To review, you replaced the entire A/C system after it was left open for more than a year without a compressor on it...a good idea IMHO.
You mentioned that you "oiled" it, vacuumed it, checked for leaks, and charged it. How did you go about doing all that, and what were the vehicle's conditions: Engine at 1,800 RPM, blowers on medium, A/C set to max cool, windows and doors open? Did you use the small 12-ounce cans of pure refrigerant containing no sealers or other additives, or a 30-pound cylinder? And did you weigh-in the precise amount of refrigerant? Did you purge the yellow hose of air before charging it? Is the clutch cycling, and are the fans coming on?
Your ambient was 112 degrees, and you said that at 232 PSI, the high side was about 100 PSI under where it should be. Actually, 232 PSI is pretty good if not a little bit low. At that ambient, with good airflow over the condenser and a full charge, I would expect to see about 250 PSI on the high side. At 55 PSI, your low side is elevated, though, which explains why you're seeing vent temps of 70-75 degrees.
You mentioned that you installed a "different" orifice tube. Do you mean a fixed OT having a different spec than the OEM part, or a variable OT?
You are correct about the refrigerant charge. Your vehicle calls for the following: All engines with rear A/C -- 68 ounces of R-134a; and in addition, 14 ounces of PAG-46.
How much oil did you put in it, and was it the correct type and viscosity?
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 7:33 am
by tbirdtbird
"I put all the new parts on"
John, what does this mean? That he changed out the evap and condenser as well?
If that original comp grenaded then as you know he has more problems yet.
I had trouble following his writeup especially when he said his hi is supposed to be 350
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 7:49 am
by JohnHere
tbirdtbird wrote: ↑Wed Jun 23, 2021 7:33 am
"I put all the new parts on"
John, what does this mean? That he changed out the evap and condenser as well?
If that original comp grenaded then as you know he has more problems yet.
I had trouble following his writeup especially when he said his hi is supposed to be 350
I took the comment "I put all the new parts on" to mean every single part of the system, but I could be mistaken. If he didn't replace the heat exchangers, as you mention, then yes, I agree with you 100 percent. But I guess we'll have to wait for the OP to respond back before we know for sure. I also agree that his post was somewhat unclear in places.
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 8:26 am
by Tim
Dual system, 350 psi is on the low side. 68 ounces is correct.
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 10:49 am
by tbirdtbird
"Dual system, 350 psi is on the low side"
Tim for some reason my brain is not wrapping around this. I have never done MVAC and had a pressure of 350. Residential, yes.
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 10:52 am
by Tim
Clarify, dual unit system. 350 psi on the high side, is correct to a little low. Dual units run a little higher overall.
Assuming you have a full charge of refrigerant.
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 2:15 pm
by Excursion2001
tbirdtbird wrote: ↑Tue Jun 22, 2021 9:13 pm
Need more info.
" I'm supposed to be at 350ish based on temp outside". That is kinda high, what is your ambient?
Did you change the dryer
Did you drain out the oil that came in the compressor, measure, and put in new of the correct amount and kind
What equipment did you use to pull a vacuum? The 'pumps' that run off compressed air will not get you low enough
How did you determine you pulled sufficient vacuum? Vacuum gauge? A system open that long is gonna need a lot of evacuation
Did the old compressor grenade? There is a reason there was no comp at all. If so the system is contaminated with the black goo of death.
How did you check for leaks
ETC.
At the time the temp out side was 112 degrees and I bought the compressor and came with no pag oil so I added the amount needed I can’t remember off the top of my head how much .I bought a vacuum pump that is electric and I have a yellow jacket Titian gauge set for r134a with in about a minute or two it pulled down to 28ish mercury I was told that since I live in a higher elevation of about 1900ft that It would alter vacuum readings by a little so I turned the pump off established that it was holding vacuum it stayed put for about 20mins so I turned it back on and let it do it’s thing for about an hour and the old compressor was from a v10 and now it has 7.3 powerstroke engine in its place so the ac compressor was removed by the previous owner and all the ac lines looked clean other than just dust from being left open and I have put iv dye and have found zero leaks
This is a does have two evaporators one in the front and one the rear they were both pretty clean when I removed them for cleaning . sorry if my post was all over the place my initial was way more in depth but it aggravated me when I went to submit it the website logged me out and I had to retype it up
Re: Low side normal /high side low stumped
Posted: Wed Jun 23, 2021 2:33 pm
by Excursion2001
JohnHere wrote: ↑Wed Jun 23, 2021 7:18 am
As mentioned previously, I think we need more information to diagnose this.
To review, you replaced the entire A/C system after it was left open for more than a year without a compressor on it...a good idea IMHO.
You mentioned that you "oiled" it, vacuumed it, checked for leaks, and charged it. How did you go about doing all that, and what were the vehicle's conditions: Engine at 1,800 RPM, blowers on medium, A/C set to max cool, windows and doors open? Did you use the small 12-ounce cans of pure refrigerant containing no sealers or other additives, or a 30-pound cylinder? And did you weigh-in the precise amount of refrigerant? Did you purge the yellow hose of air before charging it? Is the clutch cycling, and are the fans coming on?
Your ambient was 112 degrees, and you said that at 232 PSI, the high side was about 100 PSI under where it should be. Actually, 232 PSI is pretty good if not a little bit low. At that ambient, with good airflow over the condenser and a full charge, I would expect to see about 250 PSI on the high side. At 55 PSI, your low side is elevated, though, which explains why you're seeing vent temps of 70-75 degrees.
You mentioned that you installed a "different" orifice tube. Do you mean a fixed OT having a different spec than the OEM part, or a variable OT?
You are correct about the refrigerant charge. Your vehicle calls for the following: All engines
with rear A/C -- 68 ounces of R-134a; and in addition, 14 ounces of PAG-46.
How much oil did you put in it, and was it the correct type and viscosity?
Replacement was a must out here it can reach up to 130 out here and I just had a baby so the ac is kinda a priority right now lol
I don’t have a scale for refrigeration I was using the small can and made sure that I got the one with out addictives or stop leak
I’m not sure how my truck would like staying at 1800 rpm as it is a a large diesel engine with not enough air moving across the engine radiator at that rpm. I have purged the air before charging , ac clutch cycles correctly windows and everything are up I used pag 46 with uv dye , iv checked online about pressures should be based on temperature and it’s saying 55psi and 340-345psi give or take for that temp
The OT is fixed from what this guy told me on a diesel forum that it’s “supposed” slow the Freon down and make colder air come out of the vents idk if this is true or not but I’m thinking it might be the problem and since I didn’t have a scale to measure it I bought two 8oz bottles of pag46 oil and I distributed the first bottle and the 2nd bottle I divided it with a marker in the middle on the bottle and then divided it again so I would have 3 marks on the bottle top to bottom so I could get a good idea of 14oz and total and what should be left was 2 oz