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Ac High Pressure Low Pressure Specification


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#1
brian passarelli

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anyone know what the spec chart is or can contribute any info?
could use it!

what does the psi correspond to in terms of total refrigerant for a given temperature?
thanks,
Brian

Ps I seem to be a tad bit over 200 psi, high, and during operation, 30 psi low. this is with R134a in a R12 system (totally evacuated the r12 first). its 95 degrees 35% humidity in New jersey today. when i turn the a/c off, the low seems to be like 60-something, if i remember correctly. also, my compressor doesn't cut off unless im driving it will sometimes take a break.

#2
snailman153624

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Sounds like your pressure is a tad high, but that may be ok.


Should be ~45 psi on the low port when it's off, and about ~25-35 with it running, and right at 200 PSI on the high side when it's running.

#3
audiqv8

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Sounds about right. How much r134a did you put in (approx 24oz or 800 grams)? What is the vent temperature (cold air coming out of the vent)?

#4
brian passarelli

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see that's what im trying to figure out. i think i put too much in, and snailman's analysis concurs.
however, my gauge usually is about 205 on the high side, almost exactly 200 he said. howver, it is sometimes at 225 , i dont know the circumstances. but, ordinarily it's at 205.

so, i dont know how much i put in. my guess? 26 oz. EDIT**** i think more like 32 now that i think about it, but i just am not 100% certain. i know there's got to be atleast 24.
remember, I have r12 components; an unchanged( prob should have, but im looooowww on money) expansion device. side note, And i have an xh7 type brand new drier which is supposed to be r134a, whereas the old one was likely r12 xh5.

vent temp, interesting i did measure that, does the following:

at first, since its hot out, its the same as outside air: 89.8 degrees, then the follow ing happens, it begings droping quickly to 50's and slowly then, maybe a few minutes (dont know) I get to minumum of 45( 44.x's to 45.x's ) then i believe the compressor takes a break (de-clutches) the temps begin going up to about 55, then the compressor comes back on, and the temp fals to 45 ish again. is this normal for MY situation, and also implies my refrigerant capacity is acceptable? could i lose some refrigerant in order to gain cooler temps? or what?

(plenty of water from evaporator ( i have the line rerouted inside the cabin to a water bottle so i could verify the 'operation' of it ) ) , relatedly, the previous test (200psi high, vent temps)was done at night, 85 degrees (temps droping outside slowly, but humidity going up) and hood open and engine running about 1500 rpm. additionally, the humidity was seriously 86%. it was 'soupy' as reporters called it, i called it hella muggy.

#5
brian passarelli

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"At 75°F, R-134a vapour has a volume of 0.5119 cubic feet per pound."
"At 75°F, R-134a liquid has a volume of 0.0132 cubic feet per pound."

with this info, couldn't someone (say, like ME lol) use PV=nRT (physics class) to figure out the oz of refrigerant in their system, if they know the pressure - temperature relationship.
e.g. for r12, 23 degrees is close to +23 " mercury . i have heard that r134a is 85% as good,

so i would think:

P = 70 (equalized high and low, after sitting for a while, i think this is what mine is, but i'd have to check)
V= ?
n = ?> -- i think yo uwould use the
R=
R gives 0.08206 L atm / mol K
t = assuming low and high, equalize as vapour, we could use the ambient temperature (and hope that comes close (the outside/inside of car could affect the different parts but simply could just assume the same considering how low tech this is)

"2.414 L at STP has a name. It is called molar volume. It is the volume of ANY ideal gas at standard temperature and pressure."

"60 °F (520 °R) and 14.696 psia (i.e., 1 atmosphere of absolute pressure) because it was almost universally used by the oil and gas industries worldwide."

[70psi][V]=n[0.08206][80deg fah] *yeah before someone says it, i know there are mistakes in MY work, but the 'facts' are accurate, and if you know what you're doing, see if you can find the sol'n to this.

i think you could manipulate the molar voume, and stp info to figure out answer, however at the moment, my brain can't : <

r12 pressure-temp chart: http://www.longvieww...om/pressure.htm
dupont rerigerant info: http://www.suva.dupont.ca/qanda.htm
calculators (wait, maybe this can do it, without thinking too much lol): http://fridgetech.com/calculators/

#6
brian passarelli

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http://www.nzifst.or...appendix11a.htm

so its like over 65% humidity, 82 deg, hood up, night time and i did the folowing:

removed some refrigerant (not sure the amt, but "some" to bring low pressure from 30(with more refrigerant) to 26 (now with less refirgerant) [during compressor - on state])

nearly equalized before i began, and the temps were probably around 90 (residual, even though ambient was 82), the low side was about 90, high was 95 --- i ''think''. so, i guess this means i have a static pressure of 93 PSI at 90 degreess F ?

evaporator pipes:
during compressor-on state---
inlet: 61.3 degrees (F)ahrenheit
outlet: 112.5 to 114 degrees F

vent temps: sometimes it would go down to exactly 45, rarely 44.x, more often 45.x to 46.0x, due to compressor turning off, the temp would go to 51, then the temp drop cycle would occur (i presume due to compressor clutch engagement)

during compressor engagement, rpm change can be about 250 RPM, with gas pedal holding RPM at 1500, warmed up engine.

pressures: seemed like the high side could hit higher pressure if i went from 900 RPM (a/c related idle, i.e., the compressor is engaged) to quick 1500 to 2000 RPM, say like 225 or so. but normally, it was at 198-201 psi, HIGH SIDE. now, the LOW SIDE is about 26 psi.
when the compressor turns off the low side creeps up to approx 40, the high side subsides to 198(from 200.5/201) --very slowly, but then again, soon enough the compressor turns back on.



http://autorepair.ab...a/1i/bl528i.htm
http://www.fordscorpio.co.uk/acmod.htm

just various links that have cool info (pun)

#7
brian passarelli

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i think i struck gold:
http://autorepair.ab...a/1i/bl528i.htm

according to that chart, my a/c is basically right in range

#8
blackshine007

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anyone know what the spec chart is or can contribute any info?
could use it!

what does the psi correspond to in terms of total refrigerant for a given temperature?
thanks,
Brian

Ps I seem to be a tad bit over 200 psi, high, and during operation, 30 psi low. this is with R134a in a R12 system (totally evacuated the r12 first). its 95 degrees 35% humidity in New jersey today. when i turn the a/c off, the low seems to be like 60-something, if i remember correctly. also, my compressor doesn't cut off unless im driving it will sometimes take a break.

Sounds normal to me. Most a/c systems, especially in high humidity areas can get as high as 250 psi!!! At 95 degree ambient temperture, your a/c is struggling to keep the inside cool. What's the temperture coming out the vents? And do you have it set to recirculate? That makes a big difference too.

#9
brian passarelli

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i was very specific in my second to last post about the temps inside and out.

also, was in recirc, full fan speed

PS it was actually 45% humidity 95 degrees lol i made a typo error (lol), in that quote you did of me

PPS I was in a totally different, vehicle, a 2007 chevy truck . brand new, alll day long. in and out, different trips. my a/c worked slightly better (a degree or two). that makes me happy, and proud. lol and my R12 system was 'supposed' to run less efficiently as an r134a ..... hogwash! i also notice, that many r134a systems run both fans . my car only runs the a/c fan during a/c operation, and the other one only comes on as appopriate to handle the coolant temperaturs in the radiator. so , i wonder how it would work if i rigged something up so that they both came on. hehe

#10
brian passarelli

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air filter for HVAC air conditioning heater core unit . something from 1997 fsm, pretty cool nfo. i wonder if my 1993 has said filter ( i am betting it does, and i think its clogged based on what i hear sometimes and smell too)
Posted Image


temperature pressure chart (for measuring performance etc) specific to 1997 626 FSM.
my car seems right within limits (even though mine is r12 system, running r134a (see my various posts for what ive done to my system, though)

Posted Image

{wish i had had access to the fsm stuff previously eheheh}

#11
brian passarelli

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my car doesn't seem to have this filter. anyone know which cars do? e.g. do 1994's? so only 626ES have it? etc etc




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