Author Topic: LWHD1200R Window Unit. Compressor won't shut off.  (Read 10426 times)

Offline bl8tant

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LWHD1200R Window Unit. Compressor won't shut off.
« on: July 09, 2009, 10:54:16 PM »
Hi Folks,

I need a service manual for this LG LWHD1200R Air Conditioner unit AND some advice.  This unit is only a couple years old and has been flawless until the last few days.

The problem has been erratic. Sometimes the compressor won't shut off and cools the house to freezer temps.  If I raise the digital thermostat as high as it will go (86) the compressor will usually shut off.  It has also failed to come on a few times until I set the thermostat really low.

My guess is the thermistor is faulty.  Does this make sense or should I be looking at the thermostat (ie..control panel).  A service manual would certainly help me.  My next step in troubleshooting is to hold the thermistor in my hand until the compressor comes on, then hold an ice cube on it and see if the compressor shuts off.  I know those are extreme temps to test, but maybe that would give me an idea if the thermistor is faulty?

Any help would be greatly appreciated!

Thanks
« Last Edit: July 10, 2009, 09:23:48 AM by Al Capone »

Offline whirlpooltech

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #1 on: July 09, 2009, 11:29:12 PM »
Are you sure that is the correct model number?

I found this service manual for a Model: LWHD1200R Download 38 pages, 1.53MB
« Last Edit: July 10, 2009, 09:23:59 AM by Al Capone »

Offline bl8tant

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #2 on: July 10, 2009, 09:21:37 AM »
You are correct...it's LWHD 1200R.  Thanks for the manual, the parts diagram is very helpful. Unfortunately, the troubleshooting section is so-so.

I've had it on for a few hours this morning, and it's operating normally (cycling on/off and maintaining 72degrees).  But I guarantee that later the compressor will kick on and stay on.  It will cool the room WAY below the T-stat setting.  I'll see if I can get it to shut off by warming the thermistor in my hand.
« Last Edit: July 10, 2009, 09:24:10 AM by Al Capone »

Offline Al Capone

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #3 on: July 10, 2009, 09:26:39 AM »
I edited the topic to include the correct model number information.

Quote
I'll see if I can get it to shut off by warming the thermistor in my hand.

I'm not a appliance technician, but I'm thinking warming the thermistor with your hand would keep it running.



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Offline JWWebster

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #4 on: July 10, 2009, 12:04:31 PM »
Stick the probe in a cup of ice water and that should get it to shut down. If it stays running it is defective.
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Offline bl8tant

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #5 on: July 10, 2009, 01:23:36 PM »
Sure enough, it ran fine until it started getting hotter outside.

The T-stat is set at 74.  I measured the air temp in several areas of the room, and it's  between 68-69 degrees.  I put the thermistor probe against a piece of ice and after about 30 seconds, the compressor shut off.  I then warmed it with my hand to see how quickly it would come on...took about 2 minutes (I assume there is some type of delays programmed to avoid short cycling?).  It has now been running for about 15-20 minutes without shutting off and the room temp is still around 69 degrees (FYI -80 degrees outside temp).

Since the probe will stop/start the compressor (but only with extreme temps) could it still be faulty.  Maybe it's not "sensitive" enough or the resistance is out of spec?????

Thanks

Offline JWWebster

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #6 on: July 10, 2009, 01:58:48 PM »
The probe is suppose to monitor the air inside the house but this probe relies on resistance changes. If the house is too cold just bump the temp setting up a little till you are comfy. These dumb mexitronics cannot compete with the real deal.
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About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
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Offline bl8tant

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #7 on: July 10, 2009, 02:30:47 PM »
The T-stat is maxed out at 86.  I am getting some cycling of the compressor now (I stuck the probe into the fins of the evap where it would be colder), but the room temp is 67 degrees....too cold and wastes alot of energy.

Offline JWWebster

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #8 on: July 10, 2009, 07:51:13 PM »
If you have it up against the coils and still have a too cold situation then I would say the themistor is bad. I wonder if it can be replaced seperate from the control?
FYI:  A thermistor is a thermally sensitive resistor that exhibits a change in electrical resistance with a change in its temperature. The resistance is measured by passing a small, measured direct current (dc) through it and measuring the voltage drop produced.

The standard reference temperature is the thermistor body temperature at which nominal zero-power resistance is specified, usually 25C.

The zero-power resistance is the dc resistance value of a thermistor measured at a specified temperature with a power dissipation by the thermistor low enough that any further decrease in power will result in not more than 0.1 percent (or 1/10 of the specified measurement tolerance, whichever is smaller) change in resistance.

The resistance ratio characteristic identifies the ratio of the zero-power resistance of a thermistor measured at 25C to that resistance measured at 125C.

The zero-power temperature coefficient of resistance is the ratio at a specified temperature (T), of the rate of change of zero-power resistance with temperature to the zero-power resistance of the thermistor.

A NTC thermistor is one in which the zero-power resistance decreases with an increase in temperature.

A PTC thermistor is one in which the zero-power resistance increases with an increase in temperature.

The maximum operating temperature is the maximum body temperature at which the thermistor will operate for an extended period of time with acceptable stability of its characteristics. This temperature is the result of internal or external heating, or both, and should not exceed the maximum value specified.
.
The maximum power rating of a thermistor is the maximum power which a thermistor will dissipate for an extended period of time with acceptable stability of its characteristics.

The dissipation constant is the ratio, (in milliwatts per degree C) at a specified ambient temperature, of a change in power dissipation in a thermistor to the resultant body temperature change.

The thermal time constant of a thermistor is the time required for a thermistor to change 63.2 percent of the total difference between its initial and final body temperature when subjected to a step function

The resistance-temperature characteristic of a thermistor is the relationship between the zero-power resistance of a thermistor and its body temperature.

The temperature-wattage characteristic of a thermistor is the relationship at a specified ambient temperature between the thermistor temperature and the applied steady state wattage.

The current-time characteristic of a thermistor is the relationship at a specified ambient temperature between the current through a thermistor and time, upon application or interruption of voltage to it.

The stability of a thermistor is the ability of a thermistor to retain specified characteristics after being subjected to designated environmental or electrical test conditions.

I has friend in Tijuana who can git ye a good deal on a peck of these dayum mexitronics :D
« Last Edit: July 10, 2009, 08:49:21 PM by JWWebster »
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About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
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Offline bl8tant

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #9 on: July 10, 2009, 08:01:47 PM »
According to the parts diagram, it is a seperate replaceable component.  Only $4.25 (plus $7.99 for shipping :tickedoff:)

I made the mistake (sort of) of calling LG support.  The good news is they seem to think it's still under warranty (they must use a different calendar than I do cause according to mine it's been out of warranty for a year).  The bad news....there are no "authorized" service centers anywhere near me (over 100 miles away).  They won't send me the part due to "liability concerns".  (That's a phrase I've come to hate.)

SO....I may end up just ordering the thermistor myself and trying that first.

Thanks for everyone's input!

Offline whirlpooltech

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #10 on: July 10, 2009, 08:05:47 PM »
Quote
Only $4.25 (plus $7.99 for shipping Ticked Off)

Would you feel better if the part was $7.99 and shipping was only $4.25?  :)

Offline AJ

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #11 on: July 10, 2009, 08:13:34 PM »
Here is one I found at RepairClinic using the model number.

Sensor $3.80

Hope you find our site helpful.

Offline bl8tant

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #12 on: July 10, 2009, 11:55:01 PM »
AJ - Great info.  Fortunately I haven't forgot all my physics and basic electronics or that last post would have been a brain-buster. :)

Oddly enough I WOULD feel better if the part was 7.99 and the shipping was 4.25.  I do small engine repair as a hobby, and the cost of shipping on the tiny parts has become outrageous.  It bothers me to pay 8 bucks to ship an item that could be mailed in a envelope for the cost of a stamp.

Thanks Again for the help and info!

Offline JWWebster

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #13 on: July 11, 2009, 12:26:43 AM »
If I had it i would send it to ya cheaaaaap :D
May the hinges of our friendship
        never grow rusty.

About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
I love fan letters! LOL

Offline bl8tant

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Re: LWHD1200R Window Unit. Compressor won't shut off.
« Reply #14 on: July 11, 2009, 05:03:21 PM »
You may not need to send one :).....read on.

LG is apparently going to pay for a service tech to come to my house to repair the unit (from 80 miles away!).  They are even honoring the 5 year warranty even though it's just supposed to cover the compressor (1 year warranty on everything else).

This unit was a replacement for the first one I bought.  The blower went out that one 11 months after I bought it, so they sent this unit as a replacement.  That was 2 YEARS AGO. 

I have to say I'm really impressed and pleased with their customer service so far.

 

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