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Neon AC compressor cycling
Chrysler Dodge, Plymouth, Jeep, Eagle, etc info/talk (rec.autos.makers.chrysler)
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#41
 
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Re: Neon AC compressor cycling -
07-06-2004
, 10:47 PM
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"Dan Gates" <drgates (AT) magma (DOT) ca> wrote in message news:2OmdnXRJDaocNHfdRVn-iQ (AT) magma (DOT) ca... That's OK, he's never had a carload of just-off-ice hockey players in his car at -25C. They is plenty o' humidity there! And you are sure glad to get some dehumidification from the AC. |
exertion, exactly what does this have to do with ambient humidity
in the winter? <rolls eyes>
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And I know it happens, especially in the first gen. Neons because you can feel the AC compressor engaging when your are cruising along the highway. |
#42
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In article <ms7me091q7jtb9u0fq6lj4m14tjupgesv9 (AT) 4ax (DOT) com>, nospam.clare.nce (AT) snyder (DOT) on.ca wrote: On Tue, 06 Jul 2004 13:02:27 GMT, Neil Nelson <nonelson (AT) sbcglobal (DOT) net wrote: In article Pine.GSO.4.58.0407060001430.15475 (A...ngin.umich.edu>, "Daniel J. Stern" <dastern (AT) 127 (DOT) 0.0.1> wrote: Well, y'know, Neil, in Clare's little world -- I caught myself wondering the other day what color the sky is there -- all kinds of things are possible. The normal laws of physics and function just don't apply. Evaporators and radiators require replacement just because the condenser's got a leak, in his world, so surely it must be within the realm of possibility in that bizarre place for an MVAC LPCO to detect the dew point inside the passenger compartment. Well, it's been a couple of years since Clare claimed that a ballast resistor is a voltage divider, I asked him; "where the voltage is divided to?" A standard ballast resistor in series with an ignition coil IS a voltage devider. The coil sees part of the voltage, the coil sees the rest. Get a voltmeter and try it. Or to be SURE you can see it, get two. Put one meter across the resistor, and one across the coil, and ground the negative side of the coil (like closing the "points"). You will see, on a typical system, (lets say on a vehicle using a Napa IC107 coil and its associated resister) 5 volts across the resistor and 7 volts across the coil with 12 volts supplied. If you are still waiting for the answer it's because you didn't read your mail back then. Still waiting. um, Clare... Dropping voltage doesn't mean that it has been divided. |
literally divided across the resistor and the coil primary. In effect
it is a voltage divider. You would analyze it for current and voltage
nodes just like a voltage divider (current gets dropped over the "top"
resistor, and the remainder is left for the "bottom" element). There
are some a.c. interactions, but the effect is the same - i.e., the
available voltage being shared across two elements suspended between a
d.c. voltage and ground.
Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")
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#43
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In article <40EB27C1.D8ADAC0B (AT) kinez (DOT) net>, Bill Putney <bputney (AT) kinez (DOT) net> wrote: As air cools it becomes more dense, if the air is more dense it can not hold as much water vapor, if it can't hold much water vapor, what is the point of running the AC compressor in an attempt to dehumidify the intake air? Read up on "Dew Point." That is *exactly* how air conditioning lowers humidity - it cools the air before it gets to the heater, even more moisture condenses out (that "dew point" thing), then it gets heated up, so you end up with even dryer warm air. It might seem that cooling it only to have to heat it again would be counterproductive. However, the reality is that under many situations, the total effect of pre-cooled and then heated is greater than simply heating if the purpose is to keep moisture from condensing onto the windshield and decreasing visibility (it's a safety thang). All well and good Bill, but we're talking about a situation where the ambient air temperature is already low and the dew point is so low that there is very little moisture content to begin with (like Matts 20*F cite) |
windshield fogs up making driving dangerous without the a.c. working,
but does not without the a.c. working. That is a fact.
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The only reason that the mfgrs. put a limit on outside temperature before the compressor is disabled is to protect the compressor from damage. Otherwise, the a.c. would be allowed to run in defrost mode at the colder temps. So you're agreeing with me that there is a point in temperature where the AC compressor is not allowed to run because the system pressure would be so low so as to lock the compressor out. |
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In most geographical areas, a.c. inherently runs enough during the winter months to get the benefits to the compressor that Matt talks about from being in the defrost mode - Well, I'm sure that Steve Lacker can get plenty of use out of his air conditioning during the winter -months- but that is not the question, the question concerns winter -conditions-, i.e., cold temperatures, cold enough that the ambient temperature puts the system pressure below the low pressure switch's cut out point. |
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I mean it is not *always* below the compressor lockout temperature, and certainly not for months at a time. It is in Wisconsin and Minnesota and Michigan and North Dakota and Montana and New York and Alaska and probably quite a few other states not to mention large parts of Canada. And for those places that are that cold continuously for months at a time, well, that's life. Yes, it's called -WINTER- which is a big part of Matt's original premise. |
operating for defrost means the difference between a heavily fogged over
windshield and a relatively clear one that is safe for driving.
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Point is that a benefit that serves most of the owners very well is derived. You mean where it's warmer and not below freezing which was not part of Matt's premise. Years ago, when a.c.'s were not as common in autos, and the controls were truly manual without computer over-rides and complex algorithms, and the a.c. was not integrated into the defrost mode, the manufacturers indeed did advise the public to run the a.c. occasionally during the winter months for the reasons Matt cited. oh, okay.... I guess I missed the part where Matt's post was directed at owners of much older vehicles. Seen many 1962 Dodge Noens? With the automatic operation in defrost mode, it isn't necessary to give that advice, and you don't hear it anymore, and the public is less informed about the situation altogether (i.e., very few people are even aware that the compressor runs automatically in the defrost mode, even if they know what a compressor is). Well now, Matt says that they -do- give that advice and now you're saying that they don't. |
person - that's all that needs to be said. I'm not here to agree
altogether with one person and disagree with the other. I'm trying to
state reality, and let the chips fall where they may.
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I'll side with you on this one but do me a favor, check the owners manual for your Concorde and see if there's a specific recommendation about running the AC compressor in the off months to keep everything lubed. |
as already stated, that's because it is a moot point this day and time
with it being automatically taken care of with no operator interaction.
I did expect to find a discussion on the FSM about automatic a.c.
operation during defrost mode, but could find none.
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One last thing... On those old cars where it was recommended to run the AC in winter, why is it that evaporator freeze up (as in blocked solid by ice) was not a concern? Is it possibly because under winter conditions, there wouldn't be enough moisture content in the air for it to be a concern? (round and round we go) |
involvement, the windshield will not fog up in situations that it would
without a.c. involvement. Your theory is not so absolute as you imply -
for it to be valid, it has to agree with reality. You're taking certain
extreme cases, and what you are saying about those is correct.
Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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#44
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I think Matt mis-stated reality there. That doesn't make Matt an evil person - that's all that needs to be said. |
desperation?
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I'm not here to agree altogether with one person and disagree with the other. I'm trying to state reality, and let the chips fall where they may. |
Unfortunately, old wives tales and egos got in the way.
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I'll side with you on this one but do me a favor, check the owners manual for your Concorde and see if there's a specific recommendation about running the AC compressor in the off months to keep everything lubed. I already checked and wasn't surprised to find no mention of it. But, as already stated, that's because it is a moot point this day and time with it being automatically taken care of with no operator interaction. I did expect to find a discussion on the FSM about automatic a.c. operation during defrost mode, but could find none. |
certain that the AC will run in winter conditions if they make a
blanket statement that it will. At 15* F and five people in the
car exhaling moisture which is then collecting as fog on the
windshield/windows, the AC will not run and it will not aid or
assist in clearing fog from the inside of the windshield/windows,
and before you claim "extreme cases" be advised, it's a common
everyday occurrence in the northern states during the months of
January, February and December.
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One last thing... On those old cars where it was recommended to run the AC in winter, why is it that evaporator freeze up (as in blocked solid by ice) was not a concern? Is it possibly because under winter conditions, there wouldn't be enough moisture content in the air for it to be a concern? (round and round we go) You can argue the theory all you want. Again, fact is that with a.c. involvement, the windshield will not fog up in situations that it would without a.c. involvement. |
as it may be) it is a question of whether there -will- be
involvement, not whether it will be beneficial when there is.
I have not nor would I ever claim that AC does not assist in
defogging vehicle glass. i simply made two points to correct
erroneous beliefs; 1) the AC compressor will not always run if
the temperature is cold enough, 2) ambient humidity eventually
gets to a point where AC assisted defogging is not an issue.
I can't help it that a gaggle of weak tits trotted out all manner
and species of red herring in the form of airplanes, altitude,
snowfall, heavy breathing/sweaty hockey players and how their
1969 Rambler Ambassador behaved.
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Your theory is not so absolute as you imply - |
correcting him.
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for it to be valid, it has to agree with reality. You're taking certain extreme cases, and what you are saying about those is correct. |
be glad to point out all the cars driving down the road with
fogged up windshields and windows due to the fact that below a
certain temperature, the vehicles AC will not run because the
pressures are too low to allow compressor clutch engagement.
#45
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Sorry - but in this case it does. You have a nominal 12V that is literally divided across the resistor and the coil primary. In effect it is a voltage divider. You would analyze it for current and voltage nodes just like a voltage divider (current gets dropped over the "top" resistor, and the remainder is left for the "bottom" element). There are some a.c. interactions, but the effect is the same - i.e., the available voltage being shared across two elements suspended between a d.c. voltage and ground. |
For the benefit of those who haven't taken to inventing their own
definitions;
http://www.allaboutcircuits.com/vol_1/chpt_6/1.html
#46
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In article <40EB27C1.D8ADAC0B (AT) kinez (DOT) net>, Bill Putney <bputney (AT) kinez (DOT) net> wrote: As air cools it becomes more dense, if the air is more dense it can not hold as much water vapor, if it can't hold much water vapor, what is the point of running the AC compressor in an attempt to dehumidify the intake air? Read up on "Dew Point." That is *exactly* how air conditioning lowers humidity - it cools the air before it gets to the heater, even more moisture condenses out (that "dew point" thing), then it gets heated up, so you end up with even dryer warm air. It might seem that cooling it only to have to heat it again would be counterproductive. However, the reality is that under many situations, the total effect of pre-cooled and then heated is greater than simply heating if the purpose is to keep moisture from condensing onto the windshield and decreasing visibility (it's a safety thang). All well and good Bill, but we're talking about a situation where the ambient air temperature is already low and the dew point is so low that there is very little moisture content to begin with (like Matts 20*F cite) |
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The only reason that the mfgrs. put a limit on outside temperature before the compressor is disabled is to protect the compressor from damage. Otherwise, the a.c. would be allowed to run in defrost mode at the colder temps. So you're agreeing with me that there is a point in temperature where the AC compressor is not allowed to run because the system pressure would be so low so as to lock the compressor out. |
that some car makers suggest running the AC in the winter. Never said
that was a temperature below which it wouldn't run.
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In most geographical areas, a.c. inherently runs enough during the winter months to get the benefits to the compressor that Matt talks about from being in the defrost mode - Well, I'm sure that Steve Lacker can get plenty of use out of his air conditioning during the winter -months- but that is not the question, the question concerns winter -conditions-, i.e., cold temperatures, cold enough that the ambient temperature puts the system pressure below the low pressure switch's cut out point. |
cold parts of the country.
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I mean it is not *always* below the compressor lockout temperature, and certainly not for months at a time. It is in Wisconsin and Minnesota and Michigan and North Dakota and Montana and New York and Alaska and probably quite a few other states not to mention large parts of Canada. |
are rarely below 25 or 30 degrees (the two temps I believe you mentioned
earlier for R134a and R12 systems) for weeks on end or even days. Look
at the average temps and you will see that they aren't far below these
temps, which means that the highs are often above.
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And for those places that are that cold continuously for months at a time, well, that's life. Yes, it's called -WINTER- which is a big part of Matt's original premise. |
mentioned 6 states out of 50. Hardly and overwhelming majority.
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Point is that a benefit that serves most of the owners very well is derived. You mean where it's warmer and not below freezing which was not part of Matt's premise. |
mouth to support your argument. When you asked for a temp, I said 20F
as I'm pretty sure that my AC has engaged at OATs in that neighborhood.
You said that typical AC systems will not cut out until 25-30F. It
may well be 25F under the hood when it is 20F outside, so this isn't
inconsistent at all.
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Is it possibly because under winter conditions, there wouldn't be enough moisture content in the air for it to be a concern? (round and round we go) |
the car that is the problem, not the moisture in the outside air? Where
do you live? It seems pretty obvious that you don't live anywhere that
has a winter worth talking about as you seem oblivious to the issues we
face in the winter.
Matt
#47
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In article <XaHGc.103$U45.38@lakeread04>, "PC Medic" <NOT (AT) home (DOT) net> wrote: Yup, automatically. (think about that) I never said that the AC compressor wouldn't engage when defrost was selected. But that doesn't mean that it will always come on no matter what the outside temperature is, because it won't if the temperature is low enough. Well what do *you* consider low enough. I know from my years in New York that that the compressors on my newer vehicles engaged when in the defrost mode even in some pretty damn cold whether (as in well below freezing). I've posted the numbers in another reply, so I won't be repeating them. How can that be if it's falling out of the sky and collecting on the ground? Certainly isn't *DRY* ice coming down! Where do you think all that moisture that is creating the snow is coming from...the humidity in the air. When humidity level and dew point meet ...viola! moisure. Warm temp = Rain Cold temp=snow Um, no... You claimed that cold air does a pretty good job of holding moisture. Snow is not moisture held in the air, it has already precipitated out. |
supercooled droplets. And their is a phenomenon known as "winter fog"
which forms at temps below freezing.
Matt
#48
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In article <40EBD1E2.DE16F239 (AT) kinez (DOT) net>, Bill Putney <bputney (AT) kinez (DOT) net> wrote: Sorry - but in this case it does. You have a nominal 12V that is literally divided across the resistor and the coil primary. In effect it is a voltage divider. You would analyze it for current and voltage nodes just like a voltage divider (current gets dropped over the "top" resistor, and the remainder is left for the "bottom" element). There are some a.c. interactions, but the effect is the same - i.e., the available voltage being shared across two elements suspended between a d.c. voltage and ground. For the benefit of those who haven't taken to inventing their own definitions; http://www.allaboutcircuits.com/vol_1/chpt_6/1.html |
resistances in series does NOT constitute a voltage divider?
Matt
#49
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Neil Nelson wrote: In article <XaHGc.103$U45.38@lakeread04>, "PC Medic" <NOT (AT) home (DOT) net> wrote: Yup, automatically. (think about that) I never said that the AC compressor wouldn't engage when defrost was selected. But that doesn't mean that it will always come on no matter what the outside temperature is, because it won't if the temperature is low enough. Well what do *you* consider low enough. I know from my years in New York that that the compressors on my newer vehicles engaged when in the defrost mode even in some pretty damn cold whether (as in well below freezing). I've posted the numbers in another reply, so I won't be repeating them. How can that be if it's falling out of the sky and collecting on the ground? Certainly isn't *DRY* ice coming down! Where do you think all that moisture that is creating the snow is coming from...the humidity in the air. When humidity level and dew point meet ...viola! moisure. Warm temp = Rain Cold temp=snow Um, no... You claimed that cold air does a pretty good job of holding moisture. Snow is not moisture held in the air, it has already precipitated out. Cold air can hold a fair bit of moisture, including in liquid form as supercooled droplets. And their is a phenomenon known as "winter fog" which forms at temps below freezing. |
#50
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In article <XaHGc.103$U45.38@lakeread04>, "PC Medic" <NOT (AT) home (DOT) net> wrote: Yup, automatically. (think about that) I never said that the AC compressor wouldn't engage when defrost was selected. But that doesn't mean that it will always come on no matter what the outside temperature is, because it won't if the temperature is low enough. Well what do *you* consider low enough. I know from my years in New York that that the compressors on my newer vehicles engaged when in the defrost mode even in some pretty damn cold whether (as in well below freezing). I've posted the numbers in another reply, so I won't be repeating them. |
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How can that be if it's falling out of the sky and collecting on the ground? Certainly isn't *DRY* ice coming down! Where do you think all that moisture that is creating the snow is coming from...the humidity in the air. When humidity level and dew point meet ...viola! moisure. Warm temp = Rain Cold temp=snow Um, no... You claimed that cold air does a pretty good job of holding moisture. Snow is not moisture held in the air, it has already precipitated out. |
the snow to form, there must be considerable moisture in the air.
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Or are you now saying that running the AC in the defrost mode will somehow help clear a windshield covered in snow? It certainly helps clear any fog/frost that may have formed on the inside of the glass and defogs much quicker. So the 90+ inches is -inside- the vehicle stuck to the windshield? |
things to your satisfaction.
I guess it is easier to some than admitting you are clueless on a subject.
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I'm really just trying to understand how poorly ya'all have thought this out... Likewise Probably because you jump from one thing to another. |
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