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LG Window AC unit troubleshoot questions


Meterguy's Avatar
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Join Date: Oct 2017
Posts: 2
FL

10-18-17, 09:38 PM   #1 (permalink)  
LG Window AC unit troubleshoot questions

greetings all and thank you for reading.

some background.
i purchased my LG 22,500 BTU LW2415HR 240V AC/Heat unit in 2015 to cool my livingroom. it replaced a previous Maytag MED24E7E-B 240v unit that lasted 12 years that failed for a bad blower motor.

so the new one has been running for almost 2 years without issue. several months ago i started noticing occasionally while running the blower motor would shut off but the compressor would stay running. finally the blower motor appeared to not run at all, while the compressor still runs.
i took the front off, pulled the controls out for access, i noticed that the blower motor actually turns a little on low fan speed, but when its on high, it actually slows down some. reading online theres lots of reference to the cap going bad, i pulled the cap and took it to a AC repair place, they tested and said the cap is fine. the cap specs....its a dual, 55MF/6MF 370/400VAC part number
CBB65A-1

i decided to try a new one just in case so i installed and it was doing the same slow/slower and comp on.
out of curiosity i flipped the cap leads so the blower would get the 55MF and it started up much faster, closer to normal but still slower and made alot of humming so i immediately turned off the unit after maybe 3 seconds on.

during all tests the shaft spins freely

so ive taken resistance readings of the leads of the motor as follows
orange is common
O to Red (low) 42 ohms
O to Blue (medium) 34.6 ohms
O to Black (high) 23.9 ohms
i checked resistance from each wire to case ground, no shorts
i also checked speed leads to speed leads to see what that looked like
Red to Blue is 7.7 ohms
Blue to Black is 11 ohms
Red to Black is 18.5 ohms

i decided to pull the motor to see how easy it would be to replace, it was actually pretty easy, so with the motor pulled i took it apart thinking maybe i would see some arcing or burned windings, but for the most part it all looks good and i didnt see anything burned.

do you guys have any ideas. im prepared to replace the fan motor, but figured i would post here first to tap your collective knowledge.

thanks
John

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Last edited by Meterguy; 10-18-17 at 10:56 PM.
 
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clocert's Avatar
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Posts: 1,428
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10-19-17, 08:34 AM   #2 (permalink)  
One more thing to check, if the 240V reaches blower terminal, if it does, then replace the blower and make sure you get the correct CAPs.

 
Texasmark1's Avatar
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Join Date: Nov 2017
Posts: 1

11-14-17, 04:16 AM   #3 (permalink)  
Posted By: Meterguy greetings all and thank you for reading.

some background.
i purchased my LG 22,500 BTU LW2415HR 240V AC/Heat unit in 2015 to cool my livingroom. it replaced a previous Maytag MED24E7E-B 240v unit that lasted 12 years that failed for a bad blower motor.

so the new one has been running for almost 2 years without issue. several months ago i started noticing occasionally while running the blower motor would shut off but the compressor would stay running. finally the blower motor appeared to not run at all, while the compressor still runs.
i took the front off, pulled the controls out for access, i noticed that the blower motor actually turns a little on low fan speed, but when its on high, it actually slows down some. reading online theres lots of reference to the cap going bad, i pulled the cap and took it to a AC repair place, they tested and said the cap is fine. the cap specs....its a dual, 55MF/6MF 370/400VAC part number
CBB65A-1

i decided to try a new one just in case so i installed and it was doing the same slow/slower and comp on.
out of curiosity i flipped the cap leads so the blower would get the 55MF and it started up much faster, closer to normal but still slower and made alot of humming so i immediately turned off the unit after maybe 3 seconds on.

during all tests the shaft spins freely

so ive taken resistance readings of the leads of the motor as follows
orange is common
O to Red (low) 42 ohms
O to Blue (medium) 34.6 ohms
O to Black (high) 23.9 ohms
i checked resistance from each wire to case ground, no shorts
i also checked speed leads to speed leads to see what that looked like
Red to Blue is 7.7 ohms
Blue to Black is 11 ohms
Red to Black is 18.5 ohms

i decided to pull the motor to see how easy it would be to replace, it was actually pretty easy, so with the motor pulled i took it apart thinking maybe i would see some arcing or burned windings, but for the most part it all looks good and i didnt see anything burned.

do you guys have any ideas. im prepared to replace the fan motor, but figured i would post here first to tap your collective knowledge.

thanks
John
The controls for the unit are in the electronic/electronics module, a Zinc plated sheet metal can with a removable cover. This unit is on the top front of the AC unit on mine. Pop the cover and look for the large circuit card. To remove the care be very careful with the connections and check for locks.....little tabs on the side of some connections that have to be pulled back to pull the connector out. On the cable that is flat plastic, the plastic "wire circuit" just pulls out of the connector. The card is held in place with a couple of screws.

The compressor is controlled by it's own black plastic relay on the control circuit board. On my 15,000 BTU unit the part number of the card "assembly" in the upper right hand corner of the board is ASW: EBR651075. On that board are 4 relays, (black rectangular objects). You may have a different part number but you are looking for the (1) large, black, rectangular component. It may have 2 spade male connectors sticking out the top like mine which aren't used on my unit.

The 3 small black rectangular objects are also relays but are for the fan speeds; one per speed (Low, Med, High). They supply voltage to the correct winding of the fan when you select a fan speed; 3 fan speeds on my AC and 3 relays.

The large one controls the compressor. On my board the manufacturer is Sanyo and the part number is SKF-112DM stamped right on the side of the relay. Your part number may be different if your BTU capacity is different than mine. You can plug that part number into the ebay search engine and come up with that exact Sanyo relay from China for about $4 and a couple bucks shipping. Takes about a week to get it.

What happens is that over time the contacts on the relay pit due to arcing caused when the contacts open. Over time the arcs cause, what WAS a pair of smooth surfaces making contact to one-another, to become pitted like the tops of mountains (think about a mountain top and an inverted mountain top trying to make contact) and as a result the surface area carrying the power to the AC compressor is restricted to a very small area of the contacts which overheats and actually weld together.

Since they are welded, when you turn the unit OFF, or when the thermostat is supposed to turn off the compressor as the room has reached the desired temperature, the signal to the relay to open is received, but the relay can't obey the command as the contacts are welded together.

On mine the problem was intermittent because a short would develop and then burn itself off then another would form and repeat the failure and it would burn off and all.

Get a relay and if you don't know how to solder an electronic circuit card, get a buddy to do it for you. You need to remove and install the new part without burning up the board etch and the relay and need a good electrical contact.

 
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