AC compressor runs all the time?

In my home AC, when the desired temp is reached, the AC compressor turns off, and the house air circulation fan will continue running if
it is set to On instead of Auto at the thermostat.
In automobile AC, I have been under the impression that the compressor runs all the time when the AC is on, even if the car is cool enough inside. (And the fan runs all the time too.)
And that with automatic automobile AC, the only thing that varies when the car reaches its desired temperature is that the blend door moves away from cooled air to warmed air.
Which means that part of the time I am routing engine heat to the passenger compartment to warm the air that the AC makes too cool to put into the pass. comp. without warm air to make it less cool.
What a waste of money that would be!
Am I right?
Thanks.
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On 7/28/2012 9:56 AM, micky wrote:

The waste of money is when you spent the extra bucks to get the automatic climate control that does it...
The unit will cycle on and off if the pressure is too high or too low.
bob
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wrote:

I didn't want to buy an automatic AC but I didn't have any choice.
I only had two possibilities when my car blew its engine near Asheville NC, and they both required driving 100 miles to see them. .

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wrote:

Somebody who knows your car can probably show you how to disable the A/C compressor if you think it's costing you too much in "efficiency." Maybe. I used to pull the plug on my GM compressors in the fall, because I didn't want it kicking on when using defrost mode in the winter. Didn't need it.
--
Vic

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On Sat, 11 Aug 2012 17:53:45 -0500, Vic Smith

And for that matter, when one buys a high end model with a lot of accessories, he's likely to get automatic heater/AC. I don't know why that didn't happen with the 3 Lebarons, '84', '88, and '95. For '65 and '67 (the year they were made, not the year I bought them) I had Catalinas when the higher priced models were Bonnevilles. .
Unless one has the car made to order, but I usually buy cars 7 years old. This time it was 11 years old. Can't get those made to order.

I like having AC, even when the weather was cooler and I only used it 5 or 10 days in the year, , but I don't like how difficult it is to control it, and the heat as well. With manual heat/AC, one moves the temp lever and the output air changes temperature almost immediately, in the time in the takes the air to get from the blend door to the output vents, 2 or 3 seconds. With automatic, I change the temp and it seems to think about it, or it has a plan to gradually bring the cabin air temp to the temp I set it at.,
(I would think it would maks the air very cold or hot to quickly bring the average cabin air temp to what I set it to, and later it would back off the temp of the output air to match the set temp. But I haven't seen any evidence of this.)
On a previous GM car when I didn't want the AC running just because I had the defroster on (I don't care if it sometimes defrosts more quickly that way) I put in a switch to turn it off absolutely, until I wanted to turn it on.
Then, with my 3 Chrysler Lebarons, it had such a switch already, from the factory.
I haven't checked out this part of the wiring diagram yet, but unfortunately, rather than an on/off toggle switch, , the AC is turned on and off by a momentary switch, either the AC button or the Defrost button. so I probably can't put in an absolute switch like I did in the GM car and like the Chrysler cars came with. Well, except by running a pair of wires all the way from the AC clutch to the dashboard. So it looks like every time I turn on the Defrost, I'll have to manually turn off the AC. But this is just about turning the AC off and that's not my big problem, it's the inability to directly control the vent air temperature.

Well, that's a very good idea. At least It will take care of 8 months.

Exactly.
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Ever hear of "KISS"? It means, "Keep it Simple, Silly". Who cares if the AC comes on (or off) on Defrost. I've noted that my Defrost works a LOT BETTER when AC comes on during Defrost. Of course, if one wants to think that they know more than the engineers... Also, tinkering around like that VOIDS any or all warrantees.
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.
It is also good to have the AC run some in the winter months. Keeps the seals and other stuff lubercated. Bearings sitting in one spot long periods of time tend to develope flat spots.
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Thanks for the reply. .

That refers to design, etc, not to being controlled by the design. . http://en.wikipedia.org/wiki/KISS_principle The car has alredy been designed and they made it complicated. They made it so that turning on the Defrost turns on the AC, which is a violation of KISS. And why should I be dominated by them?

I do. It wastes gas and puts more load on the engine. .

So you care, too. You just like it the way that's it's designed.
I've noted that the defrosters works well enough without AC. Maybe we live in different areas of the country. Plus one can wipe the condensation off with a cloth. That's the fastest method.

FWIW the engineers don't know me personally, and they are driven by more factors than what I want. For example, on the Solara, when one puts the top down, all the windows go down. That's very nice except for higway trips or when I have a passenger I want to talk to, and in noisy parts of town (most places with 4 or more lanes of traffic), or when it's moderately cool outl, then I want the windows up. They don't know that.
Also on this car, unlike my previous 6 convertibles, the top won't go up or down unless I'm going under 3 mph or less.. When it's starting to rain that's not good. Then I like to put the top up when I'm going about 8 mph, which is fast enough to keep almost all of a light rain out of the car, but more than slow enough not to hurt the top. Actually 15 mph is okay,
I also do this when I'm putting the top down and leaving at the same time, and even when I'm getting home and just don't want to waste time. From the manual, I've identified the wire that prevents this, and when I find the ECU that it's connected to, I'll cut the wire.
I don't, but If I always wanted the windows up, I'd find what make them go down and disconnect it.
On a previous car, I didn't like it that the heater blew cold air until the coolant warmed up, so I put a thermal switch in the coolant hose that prevented the fan from working until the coolant was warm enough. I don't know if that is a problem with this car.
If something isn't the way I want it, I fix it if I can.

No. It voids warranties on the part of the car one has tinkered with. If they tell you otherwise and won't repair something that is unrelated to the tinkering and covered by the warranty, sue them.
I don't think I have a warranty on my 12 year old car.
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On 8/13/2012 11:01 AM, micky wrote:

This is true except you have to be going backwards. :-)

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On Mon, 13 Aug 2012 11:21:09 -1000, dsi1

LOL.
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On 8/13/2012 8:03 AM, Ralph Mowery wrote:

Yes, and that is one reason that the manufacturers made the AC come on in defrost mode. The other reason is that it dries the air, which is useful in damp conditions.
But some, like me enjoy having outside air come into the car, more or less at outside temperature sometimes. Since they got rid of windwings and the old kick panel vents, defrost brings fresh air into the car without having the noise of open windows or the blast of air in the face that you get through the AC vents in the dashboard.
Sometimes I want that air coming in the defroster duct to be cool and dry, and sometimes, I want it just for ventilation. I, as owner of the car should be able to chose when the compressor operates. Simple as that.
I should note that no American car I ever had with factory air let you turn the compressor on or off independently. But I guess that has changed over the years.
I still would prefer having windwings and kick panel vents. Even though I no longer smoke. Having the windows down in traffic is just too damned noisy.
Regards,
DAve
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wrote:

Yeah, I really miss those. For my '73 Buick, I made one, sort of. A small sheet of lucite, part of which went into the window slot, and, going up, was bent to be horizontal, and after a piece of pie shaped piece that was horizontal, bent to go up. So it blew air into the passenger compartment, on me. It was in front of the side view mirror, which kept the wind from knocking it out of the slot**.
It was fun to bend the lucite. I had a surplus 10" metal tube with a heater in it, that heated the plastic the right amount (if I didn't let it sit too long.)
But the next car, a Lebaron, had the side view mirror at the front end of the door, so there was no good place to put my vent window.
(My cousin and uncle called such a window a "no draft" because air could come in without a draft, but I opened them as wide as they could go in order to get a draft. Although on some cars I never owned they wouldn't open wide enough to do that.) My uncle smoked a lot. Two of his fingers were dark yellow.

I miss those too. Far better breeze than anything that comes out of any vent system in any car these days. Last time I had them was the '67 Ponitac convertible, which also had AC, but when AC became almost standard, everyone I think stupidly omitted the kick panel vents.
On the '65 and maybe the '67 Pontiac convertibles, I could open the vent window all the way so it blew on my face, open the kick panel vent so it blew on my leg, and (Get this) turn the sunvisor up and forward, so it blew air that would have gone over my head to blow on my face. No matter how hot it got, I had enough breeze. No sun vixor has done that since in 1967 or maybe 73.

Exactly.

Yes, you raised a couple points I forgot. Probably more important ones than the ones I did remembe about why I want to turn the AC off sometimes. .

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wrote:

Like I said before, you can probably put in a separate switch to keep the compressor off in the winter. Or unplug the wire to the clutch. Depends on the wiring in the car. For all I know some newer cars might flash an engine code if you do it. I ignore that stuff about running the A/C in the winter to "keep the seals lubed" and other such nonsense. Do you run your home A/C in the winter? Didn't think so. Anyway, I unplugged it for years on some cars with no issues. I don't do it now, because my recent cars don't use that much more gas turning the compressor, and winter haven't been as bad so I hardly use defrost anyway. Global warning probably.
--
Vic


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On Tue, 14 Aug 2012 21:52:50 -0500, Vic Smith

Well, this is embarrassing. Another senior moment, maybe. My OP was only about whether the compressor ratn all the time when the AC was on, but there's always thread drift and somewhere along the line, I thought I couldn't turn off my Toyota AC when the defroster was on. It's true that turring on the defrroster turns the AC on, but I can turn it off a second later. Sorry I said otherwise. It's not as good as the Chrysler AC from MY pov, but I know they can't make everything just for me.

No, and I don't think anyone else does. Good point.

On one of my Lebarons, the power steering leaked, and I had heard that the fluid had to be there to lube the pump. That's probably true on some cars,, but eventually I got tired of filling it up every few days, so I stopped for months. I had no PS, which only matters when one is going slow. Months later I added some fluid and everything worked good as new. Did this a couple more times for months at a time, PS always worked fine when filled.

Mine might not either. It seems that way but I haven't really checked.
and winter haven't been as bad so I hardly use

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micky wrote:

Nope. The home A/C units use a sealed motor with no external seals. The auto A/C uses a pair of seals plus internal seals which will get stiff and fail.

Not what usually happens, BUT I would bet that not all of the fluid leaked out either. Unless the leak was right in the bottom of the pump or reservoir there would have still been fluid enough to keep the pump lubed.

--
Steve W.

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Atleast someone understands the differance in a home sealed unit and the compressor on a car that is driven externally and has external seals to leak.
Also I have a heatpump for the house so it runs most every day.
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wrote:

Good point. Hermetically sealed. I give up.
--
Vic

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micky wrote:

Using full auto, the compressor will run most of the time unless its below about 43F ambient. IMO, its a waste of money and fuel. With many cars you can turn off Auto. Foreign made cars tend to have a switch to turn the compressor on and off with out disturbing the rest of the settings. American cars do not have that. We like to use lots of gasoline.
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micky wrote:

Depends on the car and the design of the system. Many cycle the compressor based on pressure in the system and exterior temperatures. Others cycle heat/cold to achieve the desired interior temp.
--
Steve W.

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