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Brad Albing

Servo Seems Absent in Automotive HVAC

Brad Albing
brook.d
brook.d
8/5/2014 2:00:13 PM
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Newbie
Absent or not, one thing is clear
Absent or not, one thing is clear, all drivers prefer to drive a car that is equipped with the HVAC system, it's better to be there than absent. Those who will choose the Rocklandchryslerjeepdodge source to look for a new car, won't be disappointed, most cars are equipped with the latest technologies in the automotive industry.
 


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Brad Albing
Brad Albing
3/28/2013 1:35:02 PM
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Blogger
Re: happy with my car's system
I expect if I go to the higher trimline or the more expensive model, these problems would miraculously vanish.

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Brad Albing
Brad Albing
1/24/2013 10:08:19 AM
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Re: happy with my car's system
CJ - admittedly, the system is a bit more complex than my description. However, since some cars have systems that work fine, I know it can be done. Thanks.

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Cookie Jar
Cookie Jar
1/24/2013 9:57:17 AM
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Newbie
happy with my car's system
I find my newer HVAC automatic system vastly superior to the older ones.  Back in the '70s GM used electronic control over vacuum actuators.  They were servo systems, but performed rather poorly.  When the vacuum supply hose melted on the exhaust manifold, I got full fan full heat on one of the hottest days of the year.  I suppose you could call that the fail safe mode.  Better than freezing in winter.  Even when working, I was always adjusting the temperature knob on the older systems.  In fact I found simple manual controls better thorough the years.  But I must admit, my 2007 Buck Lucerne has excellent temperature control with a separate setting for the passenger.

I believe the problem in many systems is the sensor part of the loop.  You cannot just stick a thermistor on a black dash and expect it to read your perceived temperature.  Sunshine and shadow on the sensor and defrost mode made the older systems freeze and fry.  Another fly in the ointment is the sun's InfraRed hitting the person on one side of the car and not the other and making him uncomfortable.  Even a perfect system would have to  allow for the clothing worn in summer and winter.  Somehow the 2007 version works very well and I only adjust it a couple of degrees as I get up to temperature to get the temperature just right.  Another complicating factor of course are heated and cooled seats as well as heated steering wheels.  There's more to the design than meets the eye.



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eafpres1
eafpres1
1/23/2013 11:27:40 PM
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Blogger
The C in Automotive HVAC isn't for Control
Hi Brad--I share your view.  My guess is some systems simply change the position of the valve which regulates the amount of coolant that flows through the interior heat exchanger.  That what the knobs & sliders did--the motion moved a rigid cable wire which was connected to a lever which operated the valve.  Most of those systems I've had "featured" an inflection point right about where you wanted to stabilize the temp.  So you constantly adjusted back and forth.

I know there are systems with actual temperature sensors and controllers, but if the valves are very non-linear, and the air-dampers are too, and the sensors are in bad places (all in the dash?) then it still won't work well.

I always enjoy getting a rental car with 2 front zones and seeing if I can drive it crazy setting one way hot and the other side cold so they fight it out. 

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Michael Dunn
Michael Dunn
1/23/2013 12:27:06 PM
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Blogger
Monkey AC
Back when my AC still worked, anything other than the coldest temperature setting was terribly inefficient. The AC was always on full, but warmer teperature settings would mix in warm air. I bet most cars still do this – at least the cheaper ones.

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