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on the first video discussing thermal fuses and hi limit tstats
There are seven videos in that lesson. Counting from the top, which one are you referring to?
Update – sorry, I had looked at the wrong unit. I see which video you’re talking about. We’ll get back to you shortly.
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This reply was modified 1 year, 9 months ago by
Susan Brown.
Chassis refers to the metal framing of the appliance. The chassis is grounded either at the terminal block or at the circuit breaker, depending on whether it’s a three-wire or four-wire configuration.
The power supply is Line and Neutral, not Line and Ground. However, in a three-wire configuration, any bare metal place on the chassis– frame, screw head, etc– will work as a Neutral reference point for your voltage measurements. This is because Neutral and Ground are bonded right at the terminal block in the back of the dryer. So chassis IS Neutral in a three-wire configuration.
This is not the case with a four-wire configuration because Ground has its own connection all the way back to the circuit breaker box. So at the appliance, Neutral and Ground are not bonded. This means Ground is not a reliable substitute for Neutral in a four-wire configuration. How do you know the Ground wire isn’t broken on its way back to the circuit breaker box? Is the Ground actually attached in the circuit breaker box? I’ve seen lots of stupid sh*t when it comes to wiring (and plumbing) and I’ve seen techs get head faked by using Ground as their reference, thinking it’s always equivalent to Neutral. Not always true!
This webinar recording at Appliantology goes into some more detail about this distinction. You can watch it over at Appliantology here: https://appliantology.org/topic/82369-dryer-cord-wiring-weirdness/
Troubleshooting control boards is not something you will be doing at first. The first thing to master is troubleshooting circuits in an appliance using the schematic in the tech sheet. Sometimes your troubleshooting reveals a failed main board and you replace the board.
The big problem with troubleshooting boards is that the manufacturers do not make the detailed circuit schematics for the board available to us. How do you troubleshoot circuits without a schematic? It pretty much comes down to inspecting and guessing. Sometimes, the problem is visible, like a burned trace or a burned triac. Other times it’s not because a component has failed internally with no visible signs.
The other problem is that to test any of the individual components on the board, you would need to unsolder at least one lead on the component, like a diode or a capacitor, in order to test it. This quickly becomes a time consuming job that is much less profitable than simply replacing the board. Whatever markup you make reselling a board that you repaired would be more than eaten up in the time you put into doing that repair.
As you learned in the Core course, if you apply voltage to a circuit with a single load, when electrons start moving in the circuit, all of the source voltage will be dropped across the load. So you won’t be calculating voltage drop in this scenario.
If there is an open in the circuit so that no electrons are moving, then you will not have any voltage dropped across the load.
Remember: Voltage is the first cause of everything else happening in the circuit. Voltage Drop is the effect of electrons being moved by the source voltage in circuit as they are forced through the resistance of the load.
They’re not available anymore. They stopped making them. But there are better ones out there now. Go to Amazon and search “portable oscilloscope”. Lots of choices.
I use several, depending on the situation:
1. First (and easiest and cheapest) method is using the teflon slides that go under the footings. You can get this at hardware stores or Amazon. They’re just wide channels of teflon (plastic) that snap together to accommodate different lengths.
2. Air sled. Expensive and not often used but when it is, it saves the day (and the floor). Since it is a capital cost, I charge a $75 surcharge whenever I have to use it. If the customer complains, I tell them they can save the 75 bucks by moving the appliance out themselves. I’m an appliance tech, not a mover or installer. For moving refrigerators, you want to make sure the slides are under the edges of the cabinet, but in the middle of the fridge where it could damage the condenser. Same with some ranges.
3. All dolly. Also expensive and not used much but it mandatory on some wall oven jobs. Again, $75 surcharge when I need to use it.
4. That little rolling stand you saw in one of my videos. Bought it decades ago through Marcone. Don’t remember what I paid but it wasn’t much. It’s light and portable, stays in my vehicle. Very useful for some washing machine jobs. Used to use it to replace the belt on the old Whirlpool belt drive washers. Since I’ve had it so long, I don’t surcharge jobs where I need to use it.
Just a side note that you typically won’t be measuring voltage drop across gas valve coils. But you will across other loads like motors.
Going back to Ohms Law, which you learned in the Core course: Voltage is the prime mover in any circuit. Nothing else happens without a voltage source to make the electrons move. If you have voltage from a power supply and a complete circuit from one side of the power supply to the other, electrons will move in that circuit. They have no choice. Unlike voltage from the supply, voltage drop is an effect produced when the voltage difference from the power supply forces electrons to move through the resistance of a load. Some or all of that supply voltage is said to be “dropped” across the resistance of the load and is given by the Ohms Law equation: E = I x R. You may want to review the Basic Electricity section of the Core course. You should watch this webinar recording at Appliantology that goes into detail with multiple examples showing this: https://appliantology.org/topic/72423-voltage-voltage-drop-loads-switches-jumpers-cheaters/
For more detailed information on how the valve coils work in a gas dryer ignition system, watch this webinar recording: https://appliantology.org/topic/63109-mst-office-hours-5222017-gas-dryer-ignition-systems/
Capacitors are reactive devices that change the phase relationship between voltage and current. Don’t worry about what that means exactly for now, just know that if you jump it out, you would be eliminating that function for a circuit that was designed to use it. Bottom line is that jumping a capacitor is not diagnostically meaningful.
You can, however, test a capacitor. The Old Skool way is to first discharge the capacitor by shorting the terminals with a jumper wire. Then set your meter on Rx100 and measure resistance. You will see the resistance low at first and then quickly rise to OL or open as the capacitor charges from your meter. Then reverse your probes and you’ll the see the same action. A better way is to use a meter that has a capacitor testing function. You just select this function, place your probes, and the meter measures the capacitance in microfarads.
Actuators use a small motor. If the motor is a single phase 120 VAC motor, you can use your cheater cord to power the motor. But the best way is to place the machine into diagnostic mode and power the actuator.
I can’t help with the specific problem in this forum but I can help you with troubleshooting strategy. Deploy the Ten Step Tango (TST) troubleshooting procedure that you learned in Core.
1. What’s step 1 of the Tango?
2. What’s step 2 of the Tango?
Step 2 is why I cannot help you with this specific problem in this forum. However, myself and other techs would be happy to help you with this specific problem in the Repair Forum at Appliantology: https://appliantology.org/forum/4-appliance-repair-tech-forum/
Also, you would benefit from watching this webinar recording on applying the Ten Step Tango to various real-world appliance problems: https://appliantology.org/topic/61228-office-hours-webinar-recording-from-12-12-2016/
Complain about no heat…
First thing how to test gas valve coil?First thing I would do is check for proper operating voltage to the gas burner assembly. You can usually do this from the control panel by reading the schematic to see which wire supplies voltage to the gas burner. The coils are part of the gas burner assembly.
There’s a video in the course that explains the gas valve coil operation. You’ve already seen some of this in the midterm exam in the Core course. You may want to review that.
Are you referring to something said in one of the videos? If so, please give timestamps so I can scrub ahead to those points and listen.
Hello sam so I can use jumper wire for only switch and loads
NO! Please watch the video again. I stress that you use jumpers to jump switches, NEVER to jump a load. This is an important concept to understand. If you start jumping loads, you’re going to get arcy-sparky.
Similarly, you would never use a cheater cord on a switch because as soon as you close that switch, arcy-sparky.
Remember the rule I said in the video: Cheat the load, jump the switch.
What about thermostat or thermal fuse
Both of these are SWITCHES, not loads. You should never see a voltage drop across a properly operating switch because a closed switch acts like a wire.
Or measure resistance you said measure amps to know if circuit is open or not
With voltage applied to the circuit and all the circuit components are functioning normally, then there will be amps in the circuit which you can measure. If you have volts but no amps, you know you have an open somewhere. Then you would use test continuity on each component including the load to see which one of them is open.
Make sense?
That’s a manual switch on the console that the customer can open or close (“turn on” or “turn off”) depending on whether they want to silence the buzzer noise at the end of the cycle.
Also, wanted to mention in the video Master Samurai Scott says there is no path to neutral for the buzzer at the 14:47 mark in the video which I think was misspeak but just thought I would bring it to your attention unless I am missing something here.
Good catch! That was a misspeak– should have said there’s no path to Line. I started off showing the buzzer shunted (Neutral on both sides). There was another misspeak– I said the switch is shunted when I was obviously talking about the buzzer. Loads get shunted, not switches.
How do you know when Jazz control boards started going into GE refrigerators? It’s kind of hard to get that info on a google search. I was just curious.
The Jazz boards were only used in Whirlpool-built refrigerators (Maytag, Kitchenaid, Whirlpool, Jenn Air).
More generally, the way you would answer this is by reading the schematic. Remember: the schematic is the FIRST thing you look at when you’re prediagnosing a problem in preparation for a service call. Most techs never even look at the schematic because they don’t know how to read them. Or, if they do look at the schematic (with their eyes crossed), it’s the last thing they do when they’re stumped and flailing around trying to “troubleshoot” an electrical problem without looking at the schematic. How does that work out? Almost always, not well. And without the schematic, they’re not troubleshooting; they’re just guessing and hoping to get lucky. I don’t rely on luck for anything. It’s all analysis and troubleshooting with the Ten Step Tango. Step 2 of the Tango is to read the schematic.
As far as getting the schematic or tech sheet so you can troubleshoot, you’ll download that from Appliantology. If it’s not already on the site, post a manual request in the Appliance Service Manual Request forum and Sam will get it for you.
For clarification I was wondering on newer gas appliances that have control boards, does the hot surface ignitor’s “wire” make an electronic connection directly to the control board (porcelain wire nut) by that terminal and on older appliances it is connected to something else?
Whether older or newer, in hot surface ignition systems with a control board, the board itself is switching one side of the power supply directly to the ignitor and the heater inside the gas valve. You’ll see this on the schematic– there will be a line drawn from one side of the ignitor to the control board (either Line or Neutral). The other side of the igniter goes through the gas valve heater (loads in series) and then to the other side of the power supply. In these hot surface igniter circuits, the board is functioning as a switch and the ignitor and valve bimetal heater are functioning as loads.
Don’t get tripped up just because there’s a control board. We’re still dealing with loads and switches. Boards can function as a load or a switch, depending on the problem. Think of control boards as software controlled switches. The board will make programmed algorithmic decisions about which loads to switch power to and when. This software is programmed into the memory storage chips (EERPROMs- electrically erasable programmable read-only memory). We are not privy to the software code so any of the logic functions that are relevant to troubleshooting must be disclosed by the manufacturer.
For example, suppose you have a dryer motor that’s not running. The dryer has a computer that controls the power supply for all loads in the dryer, including the motor. You have a good power supply for the board but the board won’t close the relay (on the board) that supplies power to the motor. Bad board? Not so fast! You as a sharp tech recognize that the board is functioning as a software controlled switch. So you ask yourself, “What other inputs might the board be looking for before it closes the motor relay to run the motor? Could be Neutral from the door switch or something else. You’ll look at the schematic for sensing lines. I have several webinars where I show sensing lines in different applications. They’re used all over the place in all computer-controlled appliances. General rule: when you see multiple lines doing the same thing going back to a control board (Neutral, Line, doesn’t matter) and one is unswitched while the others are switched, most of the times those switched lines are sensing lines telling the board about something going on in the machine. This blog post has some good discussion on this: https://appliantology.org/blogs/entry/1231-gas-dryer-not-heating-troubleshooting-with-only-a-jumper-wire/
Couple of webinar recordings at Appliantology that you should watch:
Gas oven hot surface ignition systems: https://appliantology.org/topic/62940-mst-office-hours-582017-gas-oven-service-call-after-a-parts-changing-monkey/
Voltage and voltage drop, loads and switches, jumpers and cheaters: https://appliantology.org/topic/72423-voltage-voltage-drop-loads-switches-jumpers-cheaters/
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