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Glad to help!
Your analogy is flawed. A refrigeration system with a running compressor does not have the “lid” effect because the compressor is continually “sucking” vapor to maintain a low pressure (and, consequently, temperature).
Some conditions such as higher heat loads (warm food placed inside, extended door opening, high ambient temperature, etc.) will cause the total system pressure to increase or decrease but this is normal thermodynamics in a sealed system, not the result of intermittent restrictions.
Now as I read the question – you are measuring in a live voltage test between the common terminal and the NO terminal of a switch during a live voltage test of a 12 V DC circuit.
Correct!
You should measure 12 volts because it is similar to measuring between the ground switch and the L1 of a socket.
Ground is simply referred to as “Ground” not a “ground switch.” And this is a DC circuit, so no L1. Doing the measurement described in the quiz question would be similar to measuring voltage across any open on a circuit. Whether the open is caused by an open switch or a broken conductor doesn’t matter. You’ll have voltage (assuming it’s plugging in as in the question scenario) but not current because electrons need a complete circuit to move.
Measuring from COM to NO on a switch that is in its normal state (meaning not actuated), you will measure the supply voltage because COM to NO is open in this condition.
I’m guessing “micro switch” means the circuit can be closed and carry current even when this particular small switch is open?
No, this is not true. Microswitch just refers to the style of switch shown in the lesson. They’re used all over the place in appliances. If the circuit connects to the switch by the COM and NO contacts, then this means the switch must be actuated for COM to NO to be closed (because NO is normally open, but closes when actuated). If this is not clear, let me know.
You may also want to watch this workshop recording that goes into loads and switches: https://appliantology.org/topic/72423-voltage-voltage-drop-loads-switches-jumpers-cheaters/
July 19, 2023 at 8:40 am in reply to: Internet connected Appliances making appliance repair opportunities obsolete? #25195Hi Ted,
In that webinar, I was relaying what I’ve heard manufacturer executives say at appliance service meetings. These are executive mucky-muck types. They are non-technical people who talk big and dream big without much basis in the reality of the technology. Think about service mode and fault codes on most appliances today. They claim to point techs to the defective load but in reality they rarely do that accurately. The tech still has to verify the fault code with electrical measurements and usually go on to identify the real problem. The actual problem could turnout to be a broken wire harness or some other defective load or switch. If they can’t get the fault codes to be 100% accurate 100% of the time, then there is zero possibility for them to identify and repair the correct problem remotely. Just because big wig executives say they want something does not mean it’s possible not or even ever.
Software and AI do not have the ability to think through a problem and are utterly reliant on the accuracy of the fault codes to fix the problem. This may work 10% of the time but will never be a 100% reliable solution to repair the problem.
Troubleshooting is a very human and analog skill. It is the irreplaceable skill. Too much physicality and sensory stuff going on: seeing the problem, reading the schematic, planning a troubleshooting strategy, hearing strange noises, etc. Machines cannot do this.
PCMs who are dispatched to replace a specific part (Whirlpool’s vision) are a very replaceable and interchangeable commodity. Real technicians who know how to troubleshoot the way we teach, will be irreplaceable.
@Moby- After you click the link, you have to then click the purple “Download” button to download the PDF.
PTC Positive Temperature or thermal Coefficient
Resistance decrease and temperature decreasesCould you give a time stamp in the webinar video where you heard this?
The high compressor temperature can be a symptom of air in the system but it could also be caused by an internal failure of the compressor. This is actually a common problem with these LG linear compressor models.
If air were sucked into the system, you would have both high compressor and condensing temperatures. The sealed system diagnostics units, parts 1 and 2, cover this.
If you go back to around time stamp 6:30 and listen for about 30 seconds, it seems pretty clear that my comment was specifically about the simple series circuit configuration I had been talking about up to that point. My comment was clarifying that this is not a practical circuit but only used to illustrate how capacitors work in a circuit. It was supposed to be a giveaway question. 😉
Hi Soo, sorry for the delay in replying. Any heat picked up by the evaporator must be rejected in the condenser. If the condenser is at room temperature, that is bottom line proof that the system is not moving heat. The thermodynamics module went into this in detail. If the evaporator is not covered in ice or frost (insulators) then the problem is either a leak or a weak compressor. From the model number, this is a linear compressor and, given the abysmal track record with these, it is most likely that the compressor is shot.
I never got around to making a video but I do have a blog post about this: https://appliantology.org/blogs/entry/669-rigging-and-using-a-compressor-test-cord-to-manually-operate-a-compressor/
Would you be able to disconnect l1 and l2 ,from the heating element . Put the probes on l1 and l2 ( that were just disconnected)
Why disconnect L1 and L2 from the terminals? You can make this same measurement with the wires still attached. But here’s the wrinkle…
and get 240v ?
Normally, yes. BUT I asked you what reading you would get on your meter for the situation discussed in the video where either L1 or L2 are missing. You’re close, you’re almost there!
I believe it would be phase three.
I asked what you would read on your meter if you measured from L1 to L2 in the situation in the video. Your meter shows you numbers. What numbers would the meter show you?
HINT: We’re only dealing with single-phase, split-phase power here. That means just L1 and L2 which are 180 degrees out of phase and are the result of splitting a single phase into two phases, as I explain in the second video in that lesson. Re-watch if you need to.
In the last video about half splitting. Where are you putting the neutral probe ,for testing .
Not chassis and not Ground. I’ll pick any convenient unswitched Neutral as my reference.
Wouldn’t it be the same to check the back of the machine ,where the power comes in?
That would tell you about the power supply to the entire dryer but not the specific Load of Interest (the heating element). What if a wire for L1 from the terminal block to the heating element got burnt or broken? What if the wire for L2 from the motor switch head get burnt or broken? So, it can be the same but not necessarily so.
As a practical matter, you would always verify proper power supply to an appliance before disassembling to test different loads and switches. The purpose of this video was to teach an important aspect of circuits that you will run into more than once. And it has headfaked many good techs.
I have tested l1 to neutral and then l2 to neutral. Then I would both l1 and l2.would this be the same conclusion?
I’m not sure of your question. I think you’re asking that if you check from L1 to N and L2 to N would this be same as checking L1 to L2? Let me ask you: in the situation presented in the video, what would you read as your voltage phase to phase (L1 to L2)?
Which unit and module are you referring?
I apologize for not clarifying. Module 4, Gas and Electric Dryer Technologies, Unit 6 Gas Burner Ignition Systems in Dryers, first video roughly in 40 mins title Common Failure and Test. You are explaining about the valve coils failures. One of the failures are mechanical: thermal failure and that it can be expose by heating it with a heat gun. I want to know how would a thermal failure valve looks like (picture) thank you.
These failures are usually internal and therefore not visible. Could pertain to the coil wiring opening when warm or deformation of the cylinder interfering with the valve piston that the coil needs to raise.
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