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Parts for Kenmore Air Conditioner 58072187300 - AppliancePartsPros.com
If you go to the Sears parts site they have actual part breakdown diagram.
Unfortunately AppliancePartsPros does not have access to these.
Yes it could be the heater assembly.
Below is the heater. You will notice a thermostat mounted at the bottom.
This should be 0 ohms at room temperature.
I could not find any tech specs on the unit so cannot say for sure what the heater resistance should be. I think it will be around 20 to 30 ohms.
Part number: AP4439760
The unit is made by LG ans I cannot get a wiring diagram so have to do some guessing. I am guessing that the air conditioner rune off of 120 volts while the heater runs off of the full 240 volts so I would check the power to the unit first.
Try flipping the breaker off/on slowly a couple times. Sometimes you can loose half the line without actually tripping the breaker.
Check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
Check the power at the terminal strip if it has one.
Do this with the heater off and on.
Be careful as 240 volts is lethal !!!