WD-12801T LG 2007 tripping breaker when door is closed

[M00se]

Hi,
I was looking for a little help, i have a 2007 Lg WD-12801T that is tripping when the cycle is started when the door is closed. If I start the cycle with the door open then I Get a dE code after about a min, if i close the door during the min, then the lights instantly go out.

Im a trained dentist chair tech, so im handy with this kind of thing, but I cant find the logic.
what ive done:
ive opened and cleaned the door safety interlock. – made zero difference
i disconnected the drain pump, as its on the same harness fork as the safety interlock – made no difference.
disconnected the connector with the lock and drain pump from the PCB, – this allows the machine to power back up after a trip, otherwise you cant raise the breaker until manually resetting the safety lock.

I have disconnected the main motor (brushed and in apparently good condition, no wear on the rotor from the brushes, brushed have approx 4cm travel left in them, no smells etc, turns well with no dodgy bearing grumble) – when i disconnect the motor i can shut the door, but shortly after the machine shuts off, sometimes briefly showing a pE code.

i disconnected the motor because there is one wire that runs from the same connector as the interlock and the drain pump which runs down to the motor, going into a blue cable that dissappears into the motor, this blue cable has a dead short with the blue cable next to it. I dont know if this may be a safety temp cut off and should be shorted, or if the short is the issue.

ive disconnected the heating element, it measures about 26 ohms, and disconnecting makes no difference.

ive not disconnected the water inlet solenoid as i recently tested them due to a low water pressure issue causing the machine to give iE errors, that was fixed 2 weeks ago. it was due to low input pressure, not the machines fault at all .

i dont know if the interlock is faulty or not, ive taken it apart and cleaned it, the electrical connections seem good, ie all metal parts connected to the obviously relevant pins, no shorts when the switch is open, and only 2 of the 3 pins short when the switch is closed. I assume this is normal behaviour. I have however noticed that the switch heats a little when waiting for the door to be closed. also worth noting, is that there is 226VAC measureable from the two wires of the switch harness that connect to the poles of the switch, obviously when the door is closed, these wires with 226VAC are connected, causing the breaker to trip.

is it normal for this voltage to be present?
if not, I assume i have a faulty PCB sending voltage down a cable it should, is this correct? I have continuity tested each cable, they are good, and there are no shorts between them, neither when connected nor disconnected to the PCB.

any help would be great, the machine is old, but otherwise was working well, the drum bearing is still good, and more importantly replaceable!! unlike other new machines ive seen that have RF welded drums.
id rather not send it to a landfill just yet if its possible to fix,
thanks in advance

[electrofix]

when you tried the machine with the heater disconnected did you have all wires disconnected or just 1

Dave

[electrofix]

whats going on is you have a leak to earth in one component
the most likley is the heater followed by the motor

when you measure any component like the heater it does not matter that it has a continuity what matters is it resistance to earth. thats what blows you trip

the trip measures the current entering your house by the live wire and compares it to the current leaving. If it differs by 0.03 amps it will blow the trip. whats happening is some of the current entering your machine by the live wire is not leaving by the neutral wire but leaking to earth

dave

[M00se]

electrofix wrote:when you tried the machine with the heater disconnected did you have all wires disconnected or just 1

Dave

I disconnected the two power wires, the earth was still connected.

[M00se]

electrofix wrote:whats going on is you have a leak to earth in one component
the most likley is the heater followed by the motor

when you measure any component like the heater it does not matter that it has a continuity what matters is it resistance to earth. thats what blows you trip

the trip measures the current entering your house by the live wire and compares it to the current leaving. If it differs by 0.03 amps it will blow the trip. whats happening is some of the current entering your machine by the live wire is not leaving by the neutral wire but leaking to earth

dave

Having tested with the heating element completely disconnected, and the fact that this happens right at the start of the cycle, like the moment you press go with the door shut, is it fair to rule out the heating element?

is there a way i can test the motor with just a multimeter?
ive tested the resistance across the temp probe on the back bearing of the motor, but it has about 6 wires which i cant work out what they do, it has 2 small gauge wires for what i assume to be the temp protection on the rear bearing, two wires for the brushes, and 4 or 6 (i cant remember right now) that are a mystery. It has windings where you would expect to see magnets in a motor (ie around the stator on the outer case) I assume the unknow wires are for this, ive not seen this type of motor before.

thanks for your help

[electrofix]

motor wires
2 wires armature
2 wires tachometer
2 or 3 wires field coil

test with meter on a high ohms scale ( at least 2M ohm) one probe on the casing the other then touch to each motor connection

if you disconnect it does it trip ?

Dave

[LJDomestics]

I would of changed the lock after ruling out heater and motor , ive had a couple burnout inside causing trip when go is pressed

[LJDomestics]

just read this….my bad ” opened and cleaned the door safety interlock. – made zero difference
i disconnected the drain pump, as its on the same harness fork as the safety interlock – “

[LJDomestics]

does it have a moulded plug? If so chop it off and put a new 1 on, sometimes the fault hides in plain site

[M00se]

electrofix wrote:motor wires
2 wires armature
2 wires tachometer
2 or 3 wires field coil

test with meter on a high ohms scale ( at least 2M ohm) one probe on the casing the other then touch to each motor connection

if you disconnect it does it trip ?

Dave

i had tested every wire to the case in continuity mode, and nothing, i will re test. I have also tested every single wire to the chassis and there is nothing.
I will report back shortly.

if i disconnect the motor, the machine doesnt trip, but quickly turns off, sometimes showing a PE message. Also if i remember rightly, with no motor, the 226v is not present between the two contacts of the safety interlock. The connector for the interlock has 4 wires 1 common neutral, 1 for the drain pump 1 for the interlock and one grey wone which ive followed down to the motor.

[M00se]

Both brushes read about 0.5 on the 20M ohm scale between the terminal and the case. Nothing else has any reading.

[electrofix]

ok on a 9v meter thats a bit low

we have to go further

remove both brushes and then put one meter lead on the copper commutator and the other one on the motor metal casing. we are trying to find out if the motor armature has an earth fault

Dave

[M00se]

on the smae 9v meter, on 20ohms scale, the copper Stator / rotor / whatever its called, to the case, measures 0.5ohms when the rotor is still, and spikes up to about 4 ohms when i move the rotor a bit. this with both brushes physically removed from the motor housing.

thanks in advance. If I cant suss it soon the mrs is going to buy a new one 🙁

[electrofix]

if you are measuring from the copper comutator to the motor case and you are fetting 0.5 ohms then its well had it
you should be getting a minimum of 500,000 ohms

also in this motor you have an Armature and field coil are the two components of the motor

Dave

[M00se]

its measuring 0.56 on the 20Mohm scale and all over the show when the rotor turns a little, then settles back down.

[Author]

Posts