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But does loading down impact a boards ability to send voltage to an AC load, such as through a Triac or relay?
Yes, it absolutely would! A control board’s programming runs on DC power, so if the DC power supply is loaded down, those functions would not work. This is why, in cases of loading down, you usually see that the control is completely unresponsive.
You’ve already basically got it! The unactuated state is the “normal” state of the switch. So if a contact is labelled as normally closed, and that contact is closed, you would say the switch is in its “normal” or “unactuated” state.
Let me know if it’s still unclear.
In the case mentioned in that video, you would replace the harness connector. If you simply push the wire back in, you would risk a callback where it has simply slipped out again.
All of the cold air in a single-evaporator refrigerator is made in the freezer compartment. So if the compressor is running, the freezer is getting cooling.
The damper is what controls if any of that cold air is being shared with the fresh food compartment. If the damper is closed, only the freezer is getting cooling. If the damper is open, then both the freezer and the fresh-food compartment are getting cooling.
So, to answer your question directly: yes, whenever the control calls for cooling in the fresh food compartment, it opens the damper.
It’s going to depend on how the control is programmed to run the fans, but in general, yes. If an evaporator has refrigerant flowing through it, the fan should be running so that air cycles across the coils and allows heat to transfer.
A. At 5:53 of the first video (Washer door and lid lock systems) – information on what DC will be measured, which was a quiz question. Can you please elaborate, as I was confused. I thought the answer would have been 5 VDC, but the “momentarily” thing did not make sense to me.
At that timestamp in the video, the specs are showing two different kinds of voltages. The 5 VDC mentioned there are signal voltages which communicate to the control board the state of the door lock –whether it’s locked or unlocked. On the other hand, the momentary 12 VDC is the power supply that actuates the lock, moving it from the unlocked state to the locked state (or vice versa). It is momentary because it only takes a moment for the lock to change states, at which point the power supply is switched off.
B. Video 5 on the Whirlpool Duet Washer – 31 minutes in – audience suggests the valve could be “bad,” which I’m assuming means open, and it is considered a possible explanation. This confused me, can you please elaborate. I tried to attach a screenshot to help, it didn’t work. My understanding was there is 120V present on the L1 VCH7.1 via the green meter to good neutral. The orange meter shows 0 V from VCH7.1 to VCH7.3 – if the problem was the valve is open (but neutral is good), wouldn’t that orange read 120V? I know that is sort of confusing, or at least my explanation of it, sorry.
That’s an excellent point — good spot! We should have been more clear in the video. The issue can’t be that the valve is open, since, as you correctly pointed out, our orange meter reading wouldn’t make sense. However, if the valve were shorted, that would be consistent with our readings. So the valve could be bad, but only in the specific case where it fails shorted.
A. On the schematic, how do C B and A close in order for the cold and hot water to turn on? They are in that little dotted line box at the bottom, which I assume means something. If this is just info located somewhere else in the schematic not provided here, you can skip this. I just thought I was missing something.
Those switches are controlled directly by the customer via the temperature control knob on the control panel. So the customer manually sets the state of those switches. You can see which switch corresponds to which temperature by looking at the chart labelled “TSC” right below those switches. And the dotted box around them just means that those switches are all part of the temperature switch assembly.
B. I see the 1/2 tub drain on the timer chart. How does it drain fully? I don’t see anything like that on the timer chart. I ask because I remember sometimes it drains when the motor is turned the opposite direction, so does it just drain when the 14 switches are closed?
You’ve got it — the machine drains when the motor turns in the “spin” direction.
I see that spring and spider support failures are considered terminal. Is the shock failure also usually terminal (and are shocks also referred to as dampers)?
Yes, shocks are sometimes called dampers, but no, a shock failing is not a terminal event. Those can be replaced.
The start and run windings are described as changing from being in parallel to in series.
I would need the context in order to address this properly. Do you know where exactly in the course material it states this?
I’m assuming the smaller elements are supplied with 120 VAC and the bigger elements are supplied with 240 VAC?
Usually, electric heating elements have a 240 VAC power supply, whether they’re big or small. You might see a 120 VAC electric heater in something like a warming element on a stovetop, though.
1. For this example, the customer states there is only 1 condenser. Don’t rely on the customer. But is this accurate? It wasn’t addressed as inaccurate so I didn’t know if I missed something. I would think not accurate but I only see 1 condenser fan on schematic and am unsure?
Could you please tell me which timestamp in which video you’re referring to here?
2. The 4th video – about 21:50 – disconnect the P2 connector and then measure for the data signal and you get the 3 VDC we were looking for. I do not understand. It is disconnected, why do we measure anything? I’m sorry, I did not understand this process. I understand we are trying to isolate the fans to determine which is loading down the system. I think I understand what loading down is and plan to reference the additional video. But I missed something.
What we mean by this is that you disconnect from the board the connector for the load that you suspect is loading down the system. Then, you put your meter leads on the pins that that connector was plugged into on the board. If that load was the culprit, you should be able to measure the DC voltage at the board that was previously missing.
1. In video 2, around 15 minutes in, failure modes for TDM valves are discussed. I understand the valves, differences, paths refrigerant can take, etc. I’m a little confused on the testing. “for testing – set fridge temp warmer than actual temp (so that 3 way valve should route refrigerant to freezer only, if any), monitor the defrost sensors (at the board) to see if voltage drops.” These defrost sensors are temperature sensors at the evaporator that let the board know when defrost is needed, correct? I’m looking for voltage drop – is there a chart I compare this to, like for thermistors that monitor the compartment temperatures?
Yes, the service manual or tech sheet should (if the folks putting them together did their job) have a table of thermistor voltage drops and/or resistances, showing which value corresponds to which temperature.
2. The finger test – is it ever the case that the valve body just happens to be in that position per MICOM instructions when you cut the power? So when you plug it back in to cycle it back to home, you feel nothing and then assume the 3 way valve body is broken?
The 3-way valve only moves to the home position briefly at the end of a defrost cycle and during the self test when the unit is powered on. So you should always feel the valve moving during the power on self test.
3. For general residential refrigerator – is a broken 3 way valve and sealed system repair something you usually do or get a new fridge?
Whether or not you do a sealed system repair depends entirely on the model you’re working on. For lower end refrigerators where the cost of a sealed system repair is about the same as the cost of a new unit? Most likely not. But for higher end models, built-in units, etc., sealed system repairs are absolutely worth doing.
Let me know if I properly answered all your questions. If not, please post the timestamps of the videos you’re referencing so that I can give you more detailed responses.
1. During the troubleshoot instructions, under step 3. We disconnect the AC power supply to the inverter board and connect the amp meter to one of the power supply lines. First: are we disconnecting and then reconnecting to make the inverter try to run the compressor (like a reset type thing?) or what is the reason. Second: when you say connect amp meter around one of the wires supplying 120VAC (doesn’t matter which one) – do you mean the L1 wire or neutral wire (as the two options)?
You’re on the right track — power is cycled to get the inverter to start the compressor while you’re checking amps. Upon rebooting, the control will perform a self-test, during which it tries to run the compressor momentarily. If it finds that the compressor does not run, then it is usually programmed to stop trying until power is cycled again.
As for where to take the reading, it doesn’t matter which wire you check amps on — current is the same at every point in a series circuit.
2. At 3:29 of the video, he states that the output from the inverter to the compressor is VDC that will vary in frequency. This has tripped me up before so I wanted to make sure – this is correct? And then the switches, which are at the compressor, effectively commutate this VDC into an AC like voltage? And the circuit on the other side of the compressor continues back to the inverter.
It gets into technicalities and semantics a little bit, but the output from the inverter is *commutated* DC, which is technically a type of AC. The switches that perform this commutation are electronic switches in the inverter.
Let me know if anything is still unclear.
Why wouldn’t we read 120 if we didn’t have a valid neutral?
All voltage measurements are a comparison between two points. You put one lead on the place where you want to measure the voltage, and the other lead on a reference point that you know has 0 volts of potential — that’s Neutral. If your reference point is not connected to Neutral, then your measurement is undefined.
An undefined voltage measurement with a loading meter will read 0 volts. That’s because, when you’re missing Neutral, there is not a valid circuit, and so there’s no voltage drop across your meter.
If you’re using a non-loading meter, like the VAC function of your multimeter, things can be a bit more fuzzy. You might still read 0 volts, but you could also read some ghost voltage. This is why we recommend that you always use a loading meter for AC voltage measurements.
Either way, you would not read a solid 120 VAC unless you have a valid Neutral.
Would this mean that the door switch is for sure good? You would still measure 0 across the push to start even if neutral was open because of the door switch, right?
The 0 VAC reading by itself would be ambiguous, but we did a reading before that with the switch open and got 120 VAC. We would not have gotten this reading if there were not a valid neutral. That’s how we know that we are getting a valid neutral through the door switch.
Service manual clearly stated all voltages supplied from main board. This model has 3 different Voltages, supply, feedback and signal. Was getting supply voltage and signal but no feedback.
The feedback signal is definitely not an output from the board. It is a signal generated by the motor’s Hall sensor when the rotor spins, which is then sent back to the board. So it is an input to the board, not an output.
If the manual says or implies that it is an output, then that is an error in the manual. Errors like that are not uncommon, especially in manuals that have been translated, like LG’s.
Hopefully that clears it up! This was a great question, and in the future, questions about problems you encounter on the job are usually best posted at Appliantology. That way, you can get help not just from us, but from a bunch of other experienced techs, too.
I guess with a compressor, the line voltage is supplied separately to the inverter. It is using the line voltage (AC) to put out the appropriate DC power, which the switches are commutating into effectively AC power, right? So it goes AC input from line, changed to DC output that board is actually creating but that output is effectively changed back to a 3 phase AC voltage via the switches?
Great summary! This is all correct.
For example, this BLDC compressor motor shown in the second video of 1.13 at about 15:12. The return circuit for the BLDC motor connects to the inverter. This portion is an AC circuit? That would require my meter to be in AC and requires the neutral that is connected to the inverter to be a complete circuit?
You can’t really make sense of the output of the inverter with a standard meter because it’s 3-phase power and the frequency varies widely from your standard 60 Hz power. But yes, the inverter takes a 120 VAC power supply (which consists of both Line and Neutral — you need two legs to make a power supply), rectifies that into high voltage DC power, and then commutates that into what is effectively 3-phase AC power with varying frequency.
And yes, separately from all that, the inverter also converts its 120 VAC input to a low voltage DC power supply for its internal logic.
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