I just bought an LG 8000 BTU window air conditioner, model LWHD8000RY6.
The unit has a digital thermostat, which on its lowest setting
displays 60 degrees. However, it is not possible even on this lowest
setting to get the machine to put out cold air below about 69 degrees.
Note I do not mean the machine does not have the capacity to cool the
space (a bedroom of about 175 sq') below 69 degrees, but rather, the
thermostat shuts the compressor off at 69, even when it is set at "60".
I tried moving the electronic temp sensor (thermistor?) from the front
of the evaporator to a position out in the room, thinking this spot
would be warmer & therefore the unit would run longer. This dropped the
room temp about 2 degrees further, to around 67. My wife & I would
prefer about 65, if not lower, for sleeping. Again, this is not a case
of the unit lacking the cooling capacity to reach lower temps, the
thermostat just won't turn the compressor on any lower. So I am
wondering if there is generally a way of adjusting these digital
thermostats (I had a similar issue with a unit having an old style
mechanical thermostat, the type which can be adjusted be varying the
spring tension on the thermostat, tweaking this I was able to get the
unit to attain a lower temp). Perhaps there's a trimmer pot on this
electronic thermostat which can be tweaked? As a second option, maybe I
could connect a wall mount thermostat of the type used on a central air
unit, which would be more accurate. Does anyone know if this can be
done? I'm guessing the thermostat on a window unit directly turns the
compressor on and off, and therefore has the current switching capacity
required for this, while a wall mount type for a central unit probably
signals a central control board on the furnace/ac, which has a relay
that does the actual switching. Is this the case? I could probably set
up a relay, still we're beginning to get to the point of a lot a
screwing around by that time. Anyone have any ideas?
I also have an LG air conditioner with digital controls and would like
to do the same. Mine is a rather large and expensive unit, so I am
reluctant to butcher it or risk damaging it. I am curious as to what
type of component the temperature sensor is.
If the temperature sensor for the digital controls is a thermistor
then it would be easy to make a circuit involving a central AC
thermostat (you would need a stat that uses a relay output instead of a
triac) and a couple of resistors to emulate the sensor indicating a
high temperature or a low temperature to manually control the
If the sensor is some sort of temperature sensitive transistor, it
would be a bit tougher to design a similar circuit. If it's a
thermocouple, it is even worse.
If you were to do something like this you would have to beware of
evaporator coil freeze up, especially at the temperature you wish to
run the unit at, since the temperature sensor is no longer in front of
the coil. Evaporator coil freezup can easily ruin the compressor.
Eric-Thanks for the reply. I agree about the freeze up potential, have
to keep an eye on it at least initially. I have forced it to run longer
by holding the temp sensor between my fingers for a period of time, so
far minimal frosting on the evaporator. On the other hand, it's not
that humid here at the moment. Another option might be to slightly heat
the sensor with something like a low wattage light bulb placed at a
distance, though again this is kind of a PITA, especially in a bedroom
:-/ This particular unit was fairly cheap, about $160.
I suspect you and your wife might like a 5 or 10 watt
ceramic resistor with a half amp or so at 12 volts better than
a light bulb :)
However, I respectfully suggest that perhaps you and Eric are
asking more of a home cooling unit than it was designed for and
intended to do. Think perhaps you guys liking to sleep at
65 degrees F are in a real minority. Not to mention the
cost on your hydro bill :)
My car has auto climate control. Switched to "US" mode, the
auto temp will drop degree by degree, until it suddenly jumps
to 50F. I'd assumed that meant that it would run virtually
forever, or until it reached 50 if ever. Not so, just tried
it. Something else shuts it down long before it gets that
Just my 2 cents, FWIW
A power resistor is a great idea! Why didn't I think of that!?!
Hydro bill shmydro bill ;-) I don't doubt you're correct about our
preference for low temps. We open the bedroom windows in February!
Honestly though, I have met others who also like sleeping in the cold.
I have been able to attain the desired temps with other 8kbtu window
units in another bedroom in a climate with a much higher heat load
applied; hotter weather, higher humidity, less insulation, less shade,
etc. I think the unit is capable of what I want, the thermostat just
doesn't think so ;-)
Probably the same thing, the thermostat is killing the car's AC
compressor clutch before it gets to the indicated temp. I didn't really
expect the "degrees" indicated by the unit's digital readout to be all
that accurate, but if they have a scale going down to 60, I really do
think the damn thing ought to be capable of more than 69 when used in a
space of the size etc. indicated by the btu output.
my 5K gold star window air:
limited schem on top of black plastic control box)
sensor - thermistor(non polar) in black epoxy glob:
212 = 1.2k
finger(98) = 6.6k
warm room(82) = 7.8k
32 = 26k
negative factor (hotter = lower resistance)
draw a linear chart, see if my numbers are on the line
use ohms law
-larry / dallas
BTW- if anyone trashes one of these, I would like to buy
your circuit board and keyboard/display. I have a GE I want
to teach new tricks ;-)
Thanks Larry, very interesting info. If the sensor in mine also turns
out to be a thermistor (a likelihood) it really simplifies tweaking. In
the case of your figures, you could fool the thermostat into thinking it
was 98 when it was actually 82 by shunting the thermistor with 42,900
ohms. Since the range of actual thermistor values over real room
temperatures would be fairly narrow, something along these lines would
probably be safe (only down side is the temp readout would be wrong, but
since it is anyway (says 60 when it's 69) no loss there). Also very
easy/cheap to implement.
With all this great info, seems you can't go wrong! :)
Another suggestion might be to consider using perhaps a 100k
variable rather than a fixed resistor.
A bit of tweaking might let you make the readout "wrong" by
10 degrees F, so that for instance you could more understandably
have 65 degrees read 75, etc.
I suspect they are limiting it to 69 in order to save energy (probably
an EPA regulation). The simplest solution would be to buy an A/C with
an analog thermostat. It's probably possible to modify the digital
thermostat, but you'd have to figure out how by tracking the circuit
and looking for data sheets for any ICs. It's probably custom to that
A/C and it will be impossible to find a schematic. It might be as
simple as a jumper to switch it to non-EPA mode, or you might have to
modify the temperature sensor circuit. If you modify the temperature
sensor, you'd have to live with an inaccurate temp display (eg. it
still shuts off when it thinks it's 69, but it's actually 65).
Thanks for the reply. I checked the temperature across the room on a
bedside table. Since the sensor is on the evaporator, it may very well
get to 60 right there, unfortunately it's a little cramped for living
space under the filter ;-) With mine set at 60, the lowest I could get
it in the room was 69, this on a day that wasn't more than about 74. I
attached a 100k pot in series with a 47k resistor across the thermistor,
adjusted to about 75k total (have to remove & measure to be sure) I was
able to get the room down to 61, with an outside temp of around 75. I
don't plan to keep the room this cool, but it does show the machine has
the capacity to lower the temp sufficiently if the thermostat tells it
to. Very easy mod, in case anyone else has a similar issue with a room AC.
Thanks again all who replied.
The internal temperature sensor (a thermistor) might be defective. If you
aren't electrically or electronically savvy, I'd suggest that you call an
A/C service company or remove the unit from the window and take it to a
If you can handle an electronic repair, You should download the service
manual from http://www.manualslib.com/products/Lg-Lwhd8000ry6-57469.html .
The service manual contains the full schematic of the unit, complete with
parts list of replacement parts.
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