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Just to add another angle to this excellent discussion…
On many modern appliances, Line is always present at the load but Neutral is gated on the CPU board. If you use ground as your reference and measure voltage with a loading meter, you will measure 120 VAC. Whereas if used the Neutral for your reference, you may measure 0vac (again, with a loading meter), indicating an open Neutral.
And the moral of the story is: always measure voltage potential difference between two points using the correct reference point. For AC circuits, that reference is either Neutral or another Line.
Lesson 2: Always measure AC load voltages using a loading meter, never with the VAC function on your DMM.
Hi John,
Here’s how a Master Samurai Tech would approach this situation:
– is my touchpanel getting the proper inputs? I know it takes some low DC power supply to illuminate my display. So I’m asking myself, “Am I getting that?”
If those specs aren’t called out on the tech sheet (in typical Whirlpool fashion) then I have to rely on my familiarity with the technology. Most displays will operate on either 5 or 12 vdc. So I’ll poke around the wire harness to see if that DC power supply is present or not.
– is my touchpanel putting out the proper output? Some keypads operate by shorting or going low resistance. Are all keypads verified for doing this correctly?
3. What are my specifications for that component? So I do a voltage, current, or resistance reading. Great. But what is the expected reading? The specifications are the bottom line regarding a component being “bad” or not.
In your unique situation, it may make sense to do sealed system work. You will need to spend about $2K for equipment and then practice brazing and charging in some old junker units. I taught myself sealed system work by reading a book and then practicing on appliances left at the dump: air conditioners, dehumidifiers, refrigerators…
You have the videos from the refrigerators course and you can get the practice in your basement. Once you successfully charge one or two, you got it. It’s not rocket science, just plumbing with some extra gizmos.
I know a tech who has built a very successful business where all he repairs are refrigerators and ranges, no dishwashers or laundry.
His partner does laundry.
So they don’t do dishwashers at all.
But they are very good at what they do.
No great loss on dishwashers– dishwashers are probably the least profitable appliance to work on. The nice thing about them is that they are another reason to get into a home and establish a relationship with a new customer, especially if they are the right brands: Asko, Miele, Bosch.
This is the model: strive for mastery. If that means specialization at the outset, so be it. You can increase your repertoire as you go, if that’s your long term goal.
Refrigerators are your most profitable appliance, so definitely start there.
Then ranges, ovens, stoves.
February 18, 2016 at 4:27 pm in reply to: Mod 3, Unit 2. Frozen supply line in water dispensor. #9501Hi Ron,
Post this over at Appliantology and we can look into this for you.
Thanks!
Question 1 is about repairs on dual evaporator systems and the 3 way valve. Replacement of this valve is the only place that I see that I may be doing any sealed system. Is this a job that is encountered very often and is cost effective for the customer?
Good question and one that was specifically raised at several manufacturer training classes here at ASTI. In every case, the three way valve (going by various names) is hardly ever fails and, on the rare times that it does, the failures are almost always electrical (the replaceable valve coil body– you do not need to open the sealed system to replace it.
Question 2: I have heard that if you don’t do sealed systems then manufactures will not sign you up for warranty work. The main one I was looking at doing warranty for is whirlpool, since that is the biggest market for this area. To your knowledge, is this correct?
I spoke to many servicers down here who do lots of warranty work and many had dropped Whirlpool. Too many problems, too little pay, too much hassle to get paid.
Warrant should not be the foundation of your business. COD work should be the lion’s share, well over 80%. Do warranty work for a few strategically selected high-end manufacturers to get you in the homes you want to be in to build a profitable customer base. Sub-Zero should be at the top of your list. For them, you’ll need to do sealed system work and it makes economic sense if you have that relationship.
Unless you’re strategically angling for a SZ contract, it’s not worth doing sealed system work. COD work will be rare while warranty work, which pays a pittance, will be so plentiful that it will displace far better paying COD work.
95% of your COD calls on refrigerators will be non-sealed system related.
I know– I tell some guys this and they don’t believe me because they listen to other guys who are puffed up in their fleshly minds and extoll the virtues of sealed system work, as if it’s the mark of passage for a “real” tech. These are same guys who can’t troubleshoot, can’t read a schematic, and every problem looks like a “shot of freon” or a control board. They’re basically glorified plumbers. The guys I told initially always come back a few years later and say, “I’ve been losing my ass doing warranty sealed system work. I wish I had listened you from the git-go.”
Don’t be that guy!
You have the full story now. Run the numbers and see if it makes sense for you.
These small wrenches are handy to have in your tool arsenal for occasional burner screws that are in hard-to-reach or tight places. They don’t take up much room in your tool bag and they’re not frequently used but, when you need them, they make the difference between being able to implement the repair or not.
Spark module and electrode systems are most commonly tested using the “op and swap” technique.
In most spark module-electrode systems, the spark module has multiple high DC voltage outputs connected to individual electrodes.
If the spark module is getting a valid line voltage power supply but none of the channels are outputting (no spark on any electrode), then you conclude the spark module is out of spec by simple operational observation. However, this is not the typical failure presentation.
The most common failure presentation is for one of the electrodes to stop sparking. The question then becomes: Is it the module or the electrode?
The answer to this is determined by swapping the inop electrode wire with another functioning electrode and see if the problems remains stationary or moves to the other electrode. If the problem moves, the spark module is at fault; if the problems remains at the inop electrode, the electrode itself is at fault.
I call this technique “Op and Swap.” Ees catchy, da?
My question is, to measure the input voltages from the PC board using EEP’s but how would I measure the 120 volts at the Inverter board. Can I disassemble the machine then power it up?
This depends on the specific configuration of the machine you’re working on. On most FL washers, you can do the this test from the computer board.
On most inverter-driven refrigerators, you would do this at the inverter itself in back of the refrigerator.
The schematic and layout of the machine will determine which approach makes the most sense.
February 11, 2016 at 6:49 pm in reply to: Solenoid Valves for Water Dispenser or Ice Maker Testing. #9469In another word, how do I depress the water maker or get the ice maker engage the solenoid?
The easiest way to do this is to use a test cord (you’ll sometimes hear it referred to as a “cheater cord”) to apply power to the valve. You can buy them or just make one from an old extension cord– clip off the female end, strip some insulation and wire, and terminate the black and white wires. Now take the fridge wire harness off the valve spades and put your test cord terminals on them. Plug the test cord in for a few seconds. Listen for the valve to hum. If it’s good, and there’s no blockage in the icemaker fill tube, and there’s a good water supply to the valve, water will squirt into the icemaker mold. Unplug your test cord, go around front and put your fingers in the icemaker mold to feel if there’s water.
Ees easy, da?
February 8, 2016 at 1:18 pm in reply to: Schematic Exercises: Appliances with Electronic Control Boards 3 #9442Hi Sal,
Can you please explain what the WHT(4P) WHT(3P) etc all mean? Does it mean White Connector 4 Pins or White connector 3 Pins?
That’s exactly right! It’s simply calling out a white wire harness connector with 4 pins or 3 pins to make it easy for the tech to locate it on the board.
See, you know more than you think you know! In fact, you know more than 90% of “techs” out there already doing it. Once you start actually doing repairs, you’ll gain confidence and experience, which is all you’re lacking at this point and is the easy thing to do.
As for your second question about the wire color for the heater’s Line voltage, look at the wire colors going into and out of the noise filter (labelled “N.F.” on the schematic) and then trace them out to the heater, paying attention to any line color changes as you go. It’s literally that easy– don’t overthink this stuff.
Some of these nitty-gritty details like you’re asking will become more obvious once you start getting your hands on appliances. Certain things seem mysterious until you see the application in the field, and then you’ll realize they aren’t that complicated.
As to your last comment – you are definitely ready to *start* working on appliances. Of course you aren’t at full capacity yet. You’ve still got to go through that process of getting your hands on actual appliances, applying what you’ve learned, and pulling it all together. You’re in a similar situation as I was when I started my business, but with two distinct advantages. 1 – the MST Academy courses you just took. 2 – the internet. I had to use videos in the 90’s to get a lot of my disassembly info and hope that the tech sheets were still on the appliance 😛
Spend some time on my YouTube channel, and maybe RepairClinic’s, just to get familiar with the hands-on help that is available for free to you and that will help you with the transition from online learning to hands-on doing.
Keep this in mind: it’s appliance repair, not rocket science. It’s EASY once you know some fundamental skills and technology, which you already do. Most of all, it’s FUN!
You should get a Professional Appliantologist membership, which will be an indispensable tool for you as you start to apply what you’ve learned.
Also, be sure to come to the Office Hours every Monday night where you’ll gain lots of useful insights into these things. It’s free as part of your enrollment.
You’ll gain confidence very quickly, because you are already starting out with a knowledge base that very few techs have– the mental tools to do real troubleshooting!
We discuss disassembly in the greater context of pre-diagnosis, of which disassembly is the much smaller and simpler (and, in my opinion, less interesting) part. The much larger aspect of pre-diagnosis is familiarizing yourself with the specifications and schematic, along with any algorithmic information. Use the schematic to “war game” the reported problem so you have a troubleshooting strategy already mapped out in your mind before you even walk in the house.
Disassembly info is available for free on Youtube, especially RepairClinic’s channel. Also, service manuals will have tear down info. You can download service manuals at Appliantology. If you can’t find the manual from searching the Downloads section, you can post a service manual request and someone will get it for you.
Good discussion! This also goes to inputs and outputs. In the valve example, the valve has a specified input, a 120 VAC power supply (note the use of the term power supply!) Its design output is a mechanical action: raise the plunger to let water flow in. You would have proven that the input is in spec (a power supply capable of providing both voltage and current) with your loading meter. But the output was not in spec. Therefore the only conclusion we draw as techs is that the valve is out of spec and must be replaced.
Hi Sal,
You want the Pomona test lead set: http://amzn.to/1Sritkp
Inputs to a computer board will be two things: electrical and user commands. Examples are:
– feedback voltage from a BLDC fan motor
– thermistor voltage drop
– user input commands from the interfaceCommands can be inputted directly to the computer board via mechanical linkage or through a sub board or panel that the user interacts with called out as a user interface (UI) on the schematic.
If a sub board is used, it communicates with the computer board by either serial data communication or by simply shorting the particular keypad being pressed.
The schematic will show the electrical inputs.
Did you come to the Appliantology webinar last Tuesday? We talked about this in some detail there. If you didn’t make the webinar, you can watch the recording below. All the presentation, which covers inputs and outputs on computer boards, is there but the first part of the schematic review is cutoff at the end.
https://www.youtube.com/embed/aMHFC06SZDE
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