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"Venting" on AC systems, steaming about Manual, breaking ice on AC in general

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Old 01 Jul 2013, 02:22 am
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Join Date: Jan 2013
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Default "Venting" on AC systems, steaming about Manual, breaking ice on AC in general

Going to vent on AC ( thats funny right there) and probably cover some old ground.
But I have the Chrysler Field Service manual and it seems to be a bunch of hooey for my car.
ANd no offense guys but a lot of what I read on various threads is wrong even dangerous, so I want to begin with basics for newbs like me.

Lets start somewhere. If you want the basics, read on here ; If you want to skip to my bichin, go down some

When running, the AC compressor puts SUCTION on refrigerant (R134a) via the SUCTION LINE ( the fattest hose on the system), sucking from the ACCUMULATOR (the aluminum can near the firewall) and upstream of that ( its all connected by hard tubes), the EVAPORATOR ( a radiator looking thing you can NOT see, its boxed under the dash inside the car, where your cold air comes from), sucking R134 into the compressor.

The AC COMPRESSOR compresses this (low-pressure/warm) sucked up R134a gas, (turning it into a high pressure / hot gas), then DISCHARGES the compressed hot gas (via the DISCHARGE HOSE or line) into the top of the CONDENSER (the radiator looking thing behind the grill, in front of car),

The DISCHARGE LINE is connected from compressor into the TOPMOST connection on the CONDENSER, so that the refrigerant can trickle downward back & forth through the condenser paths, shedding heat to the outside air (air helped by a the radiator fan) and ideally condenses ( turns from a very hot gas into a much cooler but still warm / even hot liquid) that pools in the bottom of the condenser.

The now liquid R134a then exits the condenser into the LIQUID LINE, where it encounters an orifice (a tiny hole / tube that is crimped INSIDE the LIQUID LINE) that means the R134 is partly blocked, but some can spray out into a lower pressure region of liquid line, thus expanding, and by expanding and turning from liquid to gas, begins to cool greatly (expansion requires heat, in other words, it feels cold). The cooling expanding gas/liquid then flows up into the EVAPORATOR continuing all the while the expansion / cooling process, and a fan blows cabin air over the evaporator and through the cabin vents to makes us feel less hot and bothered. Ideally, all the liquid is gas by then, and taken aboard all the heat it reasonably can, and sits in the accumulator until sucked out by the compressor again. Any unintended R134 liquid should stay in the accumulator, to avoid sucking an ~incompressible liquid into the compressor.

In other words, for this discussion, the system is a loop divided into two main regions, HIGH and LOW pressure, and the boundaries are at the ORIFICE and the COMPRESSOR.
R134 flow anywhere between the orifice-to-compressor (or, after orifice -to- evaporator -to- accumulator -to- suction line -to- compressor) is the LOW (pressure) cold/cool side.
R134 flow between the compressor-to-orifice (or compressor -to- discharge line-to- condenser -to- liquid line -to- orifice) is the HIGH (pressure) or hotter side.

Now comes some of the problematic stuff. WARNING don't think or tell anyone I taught you how to work on AC. Learn before you do. and not from me. There be dragons

To do AC correctly at all, you need a manifold gauge to read pressures AFTER the compressor ( the HIGH side) and somewhere well down stream in the liquid line (after the orifice), the LOW side. $60 for a HarborFreight leaker to ~$300 for some good Yellow Jackets.

To top up an AC system, R134 must be gradually sucked into the system. This is done on the low side ( where suction exists) and NEVER ON THE HIGH SIDE .. if you open the HIGH SIDE to your R134 can, you can blow it up. Thats why the bottom of R134 cans have a scribe line , so anyone making this error might not make a full on bomb, but instead the can will rip along the bottom and jet around, banging against things until it loses pressure. STill dangerous but less so.

Suffice to say NEVER OPEN THE HIGH SIDE VALVE when working on a running AC system. At best you will flood your gauge and flood the low side, at worst you will damage / blow up your gauge or blow up a r134 can attached to them. Just DONT. The only time I think one opens the high side valve is when pumping down (evacuating) a system that has been completely opened for service. You can read the high or low side pressure with the gauge valves CLOSED or OFF, as the valves simply close off the HIGH or LOW side from each other and from the yellow service line.

I am going to skip the rest of the "how to use gauges" part for now (LEARN before you get hurt) and complain about the Chrysler PT Field Service Manual (FSM), and hope someone throws me an answer or so;

I have the 2003 base NA 5-speed US model.
Turbo, automatic and foreign market have different parts accord to parts sources.

The 03 FSM seems wrong at least for my car and is sort of short of good info.

Worst of all, the FSM describes 2 possible ports on the LOW side of the system;
#1) after the 'liquid' line (hard line actually, after the joint over the engine) and before the evaporator and
#2) on the hard line between the accumulator and the compressor, the true "suction section".

The FSM however says to use the #2 port , and to never use the 'liquid line' #1 port.
BUT my system does NOT have a port on this #2 section (tho accumulator does have a LOW PRESSURE SWITCH screwed on to a Schrader valve).
It only has the #1 port before the evaporator
So much for MOPAR proof reading.

Thus I am forced to read a slightly higher pressure point for the low side checks than what the manual indicates.
I guess I could put an adaptor on the schrader ( jumper the switch too) to read the pressure on the accumulator someday but that aint cricket.

Next my system has one port for the HIGH side, located on the DISCHARGE line just after it exits the compressor.
OK but;

There are two decent tables in the FSM, and one is actually a graph showing the proper relationship between liquid line TEMPERATURE (remember, the liquid line begins after AFTER the condenser has cooled the R134) and the liquid line PRESSURE. But there is no true liquid line port ( at least between condenser and orifice , on the HIGH pressure side of the orifice), and the pressure on the HIGH port, next to the compressor, will be higher due to the hot compressed gas exiting the comp. , than it would be on the liquid line / at exit of condenser.
So much for following instructions there too !

Now, the table that lists the ambient temps, the cooled air temps and the proper HIGH & LOW pressures is good, but I prefer to consider the Pressure::Temperature graph for over and under charge, as this graph should apply even if you cool the condenser with a water mist, run it ambient, cycle, what ever. Using the P::T graph is actually what matters for a properly charged system ...

The table and graph are here, along with a decent discussion. • View topic - 1st Gen Air Conditioning Specifications for the FAQ
and I enjoyed ( despite a few errors)
03 vs 04 AC recharge - the definitive word?

and here is a another place for the P::T graph
liquid line pressure temperature graph chrysler - Google Search

Well my questions are
1) has any one deciphered the conundrum about having to measure the LOW side well upstream of the described location,
2) having to measure the HIGH side ( for the P::T graph) well upstream on the described location ?

Lastly and off the topic above, the FSM indicates there is a pressure switch / transducer on the discharge line that, in electrical series after the LOW PRESSURE SWITCH mounted on the accumulator, controls the compressor cycle. Wrong. No such transducer on my 03 stick exists. Just has that LOW P switch to signal the PCM main control module & control the compressor.

thanks for reading this far !

Last edited by gtgt_bangbang; 01 Jul 2013 at 02:47 am.
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  #2 (permalink)  
Old 01 Jul 2013, 02:56 pm
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Join Date: Sep 2001
Posts: 27,743
Default Re: "Venting" on AC systems, steaming about Manual, breaking ice on AC in general

I can only answer that last question you have. The cycling of the compressor is done by the low pressure/recycling switch that's located on top of the accumulator.

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Old 02 Jul 2013, 10:42 pm
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Join Date: Jan 2013
Posts: 44
Default Re: "Venting" on AC systems, steaming about Manual, breaking ice on AC in general

yea thats almost what the FSM agrees on, but all the wiring diagrams (and description) indicate that switch is a LOW P cut out, and there should be a CYCLING switch on the discharge line, in series beyond this LOW P switch.

and the other bugabear is the low pressure is supposed to be measured at a post at or after the accumulator, while the only low port on my car is before the evaporator.

Reading the neon site, seems these FSM errors have been long term
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Old 03 Jul 2013, 10:57 pm
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Join Date: Nov 2007
Location: Mooresville, NC
Posts: 5,324
Default Re: "Venting" on AC systems, steaming about Manual, breaking ice on AC in general

I COMPLETELY AND TOTALLY AGREE WITH YOU ON THE HIGH SIDE COMMENTS! I've had lots of fun working with HVAC units on several different vehicles and one time, way back when, I made the mistake of opening up the high side line and darned near blew off my gauges!

Now, on my PT, 2006 GT, I blew off the suction line back in October last year. Best thing about that was my mileage went up to an average of 23 mpg! However, back at the end of May, when it was getting hot and humid here, I finally decided to fix it. Replaced the suction hose, that sucked because how difficult it is to get to the connection point on the compressor. However, got it done, found other problems so even though it took a lot of effort at least I fixed up other items.

Now, after replacing that hose, I pulled the vacuum on it for about 2 hours with my fancy-schmancy dual mode 3cfm vacuum. Boy did I see a lot of steam out the exhaust pipe when I started! So that tells me I had a lot of condensation/fluid in the lines. Now I probably should have replaced the Accumulator simply because that line was open for months, but I didn't. Also, I don't believe I put enough PAG oil in the system - brain didn't think correctly about the amount of oil that had leaked out until after I'd already recharged it.

Now, in doing the vacuum is the ONLY time I opened the High side. THE ONLY! After completing that, recharge the system ONLY on the Low side, and within minutes she was up to pressure and really blowing cold air.

Now there are measurements for both the High and Low sides, but realistically I'd suggest people stay away from the high side! Once you have the system charged and running properly, the Low side pressure readings will tell you if you have the right amount charged in the system. I actually played with mine just to verify that (a) when you under-charge your system the compressor seldom stays running and you don't get cold air, and (b) when you overcharge your system the High side starts overheating and you cannot, again, produce cold air.

Now I have a very fancy set of manifold gauges, which are liquid filled so they don't bounce around, and they have some very nice connectors along with the R134a quick connects, so I can control the connections at the Low/High side connections and/or at the manifold. Makes it easy to use.

So, my AC is colder than it was when factory filled. However, she's causing rough idle and that's likely due to the amount of condensation in the system, and/or the low level of PAG oil is not enough in the system to keep the compressor properly lubricated.

All of that being said, this weekend I'm having the coolant sucked out of the system, then I'm pulling the suction hose off and adding in 3 ounces of PAG oil, maybe replacing the Accumulator, then re-sucking the system down and insuring that I suck all the snot out of it. Once that's finished, I'll go back into recharging it, and voila, will most likely have another fabulous AC system again, with no issues (hopefully). Mind you, she's so darned cold that when I'm driving I have to turn the temp up and the fan down because I was freezing in the car the last few weeks!!!!

Lastly, I don't agree with the measurements shown on that Neon site - maybe it's because mine is an '06??? I can tell you that on mine, the Low side valve is after the Accumulator, and easily accessible, while the High side valve is in a spot that TOTALLY SUCKS to try and gain access to!

Here are a couple of pics that I posted in a thread about how to vac & recharge the AC system:

Last edited by Chromenut; 03 Jul 2013 at 11:01 pm.
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Old 22 Jul 2013, 12:50 am
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Default Re: "Venting" on AC systems, steaming about Manual, breaking ice on AC in general

Aggravating intermittent AC compressor operation.

Sometimes excessive compressor cut out (shut down), most times couldn't get system to start with dash switch at all. No obvious rhyme or reason.

Cliff Notes version; At this point I am suspecting an intermittent AC clutch was due to too wide a clutch gap , that allowed the clutch to disengage on occasion or even not function at all when it was mad. Thinner spacer washers seemed to solve things.

Readers InDigestion version;
When i was charging system, although the Field Service Manual left a little to be desired (and the syst capacity label was missing from hood) I did get the system to function & cool. Even after a pretty significant overcharge, from trying to go by the pressure & temperature table oops!

The intermittent oper started in after a few doz miles of driving car post-rebuild.

No idea if AC worked properly before I got car (winter purchase), although the system was charged when I had it evacuated before dismantling for an engine rebuild. Should have checked but man it was nasty cold .

BTW had replaced replaced all the AC hoses ( some damage and scuffs, plus good deals on new parts) and the condenser ( lots of smashed fins, slightly bent and maybe leaking a bit, supposedly not flush-able), replaced the accumulator just due to open system and flushed the evaporator.

My 2003 manual tranny 10S15C compressor is probably original. No sign of leaks. Seems able to compress & cool , when it wants to .

Accumulator-mounted low pressure switch seemed functioning.
Also system did not function when bypassing LowP switch connector with jumper wire.

Had replaced the chipped-up compressor-mounted high pressure cut out switch, and that seemed OK too.
Also jumping past IT didn't fix system either.

Voltages present all along the the wires when expected (simple series circuit for most part, from battery to fuses/dash switch to relay through 2 pressure switches to comp clutch ... to evil PCM for Ground ) although I was confused by the effect of the PCM, as the manual indicates AC system operates when ground allowed by the PCM and no clues as to when that would be allowed ( did engine need to be running ? could I bypass PCM to test components ?)

Voltage through AC relay headed to compressor coil seemed very low. Not sure what to make of that right now, if it actually should be 12V. But couldn't get clutch to grab even when skipping a relay & putting 12V down to clutch through car wiring.

I was going crazy and reduced to suspecting breaks in the wire particularly down near the clutch, as several times thought I was able to start compressor my jiggling connector there. Not consistent. Maybe coincidence or ?

I was able to get clutch magnet (when removed from comp & car) to magnetize / lock up/ grab the driven half with 12V across the coil, and could not jiggle wire to disrupt connection. Not great evidence for bad wire and was worried that 12V would fry the coil wire due to oddly low V out of relay.

Measured AC clutch coil resistance; a small fraction of an ohm. Bingo, supposed to be 3~5 ohms of wire in there. Low ohms should mean fewer effective turns = weaker magnet.

Dashed down to junk yard and got lucky with only PT there, AC compressor still there complete. ( Neons from early to mid 2000's should have same comp … first one of those I measured ALSO had zero ohms. Odd. Not really a popular break down. PS Manual trans 10S15C, or auto trans 10S17C, slightly diff compressors, apparently have same coil).

The sole PT at junk yard; compressor coil ohmed at 5ohm. Double bingo. Things lookin up

Work tip - Use an oil filter gripping wrench to steady clutch to remove the 10mm head bolt holding clutch together. Only other tool needed is sturdy expanding circlip pliers and maybe 13mm to drop comp off bracket for access. Clutch pieces should all wiggle off after clips removed.

Home again, ohmed the original coil once more … WTF , it measures ~1ohm NOW; low but not a real short.
Installed salvage coil. System STILL not functioning. Double Damn.

Not much left to go on … EXCEPT …

Original spacer washer inside clutch was 1.25mm thick. FSM says a good place to start if you don't know original was 0.1" or 2.5mm. Wow, thats thick. My comp wasn't dragging when off, but I had a standard washer ~1.5mm thick so I installed that. ( NO washer installed allowed the clutch to drag a bit but not lock. Not sure now, if I tried to turn system on. Maybe a mistake there.)

At wits end, I figured to reduce the clutch gap. I took out the replacement 1.5mm washer, knew the 1.25mm was same nil result, so I put two .5mm wave washers together for ~1mm total.

Clutch functions, Sweet.

So at this point I am suspecting an intermittent AC clutch was due to slightly too wide a clutch gap , that allowed the clutch to drop out / disengage on occasion or even not function at all when it was mad or sad.

So if you are faced with an iffy clutch, you might want to do a cheap and easy to experiment with gaps. Manual wants you to dial gauge the movement of the clamping clutch, to see if within range (.015 to .025" I think ? too lazy to go look up) But I could not get clutch to grab, so how the hell can I measure clamp-up movement ?

You could feeler gauge it I suppose but its a tight bend and I could not find my narrow flexi feelers that would curve in there.

So thats my story and if I have AC going forward, I am chilling with that version.

PS , rockauto lists a lot of drive belts for this 2003, I zeroed in on an on-sale GOODYEAR Part # 4040560 Gatorback , 4 Ribs / Effective Length = 56" / Outside Length 56.75" (or a 4PK1420 size).

That belt turned out was too long, allowing tensioner to just barely bottom out before, well, tensioning. Was hard to notice as it was very close, it just seemed very loose. That was one of original goose chases in this hunt, as it threw an additional voodoo in the mix. Fished old the old belt and thank dog, could just barely make out the 4PK1395 mark in it.

So there is a bad listing part from Goodyear & RA.

Goodyear gators list Gatorback® Poly-V Serpentine Belts | Goodyear® Engineered Products

list their next smaller belts , with stops at 4PK1410 ( 55.5" effective … probably work but not much tension) then a 4PK1395 (55.0" effective … FITS ! Goes on easy, and come to learn that this size actually listed for LATER years PT with PS+AC) then bounces down to 4PK1360 (way to short at 53.5", would never get it on).

PS ACDelco & Gates list (on rock) 55 5/8" belt for this car, I just didn't even notice when I saw a GY gator for ~$5. No wonder the 56" GY is on sale ... THEY DONT WORK !

nuf said for now.

Last edited by gtgt_bangbang; 22 Jul 2013 at 01:04 am.
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