Samurai Appliance Repair Man

[Samurai Appliance Repair Man]

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/

[Samurai Appliance Repair Man]

Also, watch this webinar recording at Appliantology: https://appliantology.org/topic/72423-voltage-voltage-drop-loads-switches-jumpers-cheaters/

[Samurai Appliance Repair Man]

A belt switch is just a switch like you learned about in Core. Lots of pictures of these types of switches in the Core course or online. The switch is actuated by the tension of the belt. When the belt breaks, this tension disappears and the switch is no longer actuated. The board monitors this switch and can tell when it is no longer actuated. The software on the board attributes this to a broken belt.

secondly,its written that Under normal conditions, the pump will run for 20 seconds at the beginning of a cycle and 20 seconds at the end of a cycle, or if excess water accumulates in the sump area
does it mean that the dryer will automaticly activate the pump at the begining and end of every cycle each and every time i turn on the dryer eventough the pump area is empty? if so why do we need the pump to run on empty?

You may have missed the bolded note just below that:

Again – that was an example. Refer to the technical documents for the machine you’ll be working on!

That description from was the operating algorithm for a GE condensing dryer. That description came from the service manual. You will also get the specifics of the operating algorithm from the service manual for whatever condensing dryer you happen to be working on.

[Samurai Appliance Repair Man]

I’m not sure how you’re using the phrase “splitting the load.” But you would determine the voltage supply (and your measuring locations) for your load of interest from the schematic. You start at the load and work back to the power supply. For a 120 VAC load, you will be tracing Line and Neutral starting from the load back to the source. Sometimes, you can’t tell right away which side of the load is Line and which is Neutral. Doesn’t matter because it will be revealed to you when you complete the trace back to the source.

For a 120 VAC load, you will measure 120 VAC dropped across that load when it is running. Using the schematic, you can usually find clever and convenient locations for making this measurement, such as at the control board, without having to tear down the entire machine.

If you have your 120 VAC at the voltage supply source but no amps in the circuit, then this tells you that you have an open in the circuit– could be an switch, broken wire, bad harness connector, or an open load. You’ll use the schematic to identify the switches in the power supply circuit for that load and then use your jumper wire to jump out each switch one at a time.

[Samurai Appliance Repair Man]

It’s just a variation on the same functional theme. In other words, a different way of doing the same thing. Different valve and regulator manufacturers. The video showing you a common conversion. Many other common conversions involve flipping over the blocking pin. The exact procedure may vary slightly depending on the type of regulator but the FUNCTION is the same regardless of the procedural variation.

But here’s the bottom line: you shall ALWAYS follow the appliance manufacturer’s conversion instructions TO THE LETTER. You shall not turn to the right hand nor to the left. But you shall obey the appliance manufacturer in all their written conversion procedures. BEFORE YOU ATTEMPT THE CONVERSION, you shall obtain said written conversion procedures from the installation guide that came with the appliance. If the customer has misplaced the installation manual, you shall request a PDF of said manual at Appliantology.

• This reply was modified 2 years, 1 month ago by Samurai Appliance Repair Man.

[Samurai Appliance Repair Man]

Great job! You have snatched the pebble. Just one little tweak…

So, if we test N at T17 wrt L1 at the load and get 120 VAC, that means voltage is present up to that point in N. Then we move our lead to T13 and get 0 VAC, it means that the timer contact at T13 is stuck open and we need to replace the timer.

T13 is definitely one possibility. But Neutral has to complete through two timer switches: T17 to T16 at cam 10 and T16 to T13 at cam 8. So one of those switches is stuck open. As a practical matter, it doesn’t matter which because, either way, the timer is getting replaced. If I have 120 VAC between T17 and L1 but 0 VAC between T13 and L1, I have all the data I need to draw the correct troubleshooting conclusion: replace the timer because one of the switches in Neutral is stuck open.

I think one of the most helpful things you have said is to just focus on the LOI and it’s circuit. In the past, when I have attempted to use schematics and timer charts, I get all distracted and befuddled by processes that have nothing to do with the problem. It seems obvious, but I guess it needs to be pointed out.

Correct! This is true for any schematic analysis you do on the job. A schematic shows lots of different circuits. We don’t need to spend the time figuring out what all those circuits are doing, just the specific circuit for our LOI. We focus like a laser on the power supply circuit for the LOI and don’t let ourselves get distracted by unrelated circuits.

[Samurai Appliance Repair Man]

The video begins with a discussion that we were getting a valid L1 but the load was not running. Starting at about 15 minutes in, I list some ways of determining if you’re dealing with an open Neutral. I talk about “junk voltage” (ghost voltage) which indicates an open Neutral. But you would only see this if you’re using a meter without LoZ and measuring with the VAC function. With the LoZ function, you would read 0 VAC because the meter on LoZ bleeds off the ghost voltage and correctly reports 0 usable voltage available for that load. Then I discuss measuring from the L1 side of the LOI (drain pump motor) to a Known Good Neutral (KGN) which is going to be an unswitched Neutral somewhere on the machine (the terminal block, in this case). If I read a good 120 VAC (on LoZ) between L1 on the pump and my KGN BUT I read 0 VAC across the pump winding (again, on LoZ), then I know I’m dealing with an open somewhere in the Neutral circuit for the drain pump motor. And

So we covered several ways of testing for a valid Neutral at the drain pump: read voltage across the pump winding (knowing that we had a valid L1 at the pump); confirming by reading 120 VAC between L1 at the pump and a KGN (unswitched) Neutral elsewhere in the washer; and the ultimate acid test– using our cheater cord to hot wire the load to see if it runs. If the load runs on a cheater cord, then you have proven the load itself is functional and that the problem is in the power supply circuit for the load. Given the components in the Neutral side of the drain pump circuit (switches, harness connectors, splices, wire, etc.) we know one of those components is open.

Given your amazing new knowledge of circuits, how would you track down the location of that open in the Neutral side of the circuit using voltage measurements (that’s a hint)? In other words, we know we have a good L1 at pin 1 of the pump motor. So we can set one of our volt meter probes there. Then we can use our other probe together with the schematic to probe the circuit until we pick up our missing voltage difference.

For example, what if we had one probe at pin 1 of the drain pump (L1) and then put our other probe at timer contact 17 (T17) and we read 120 VAC. Yet we read 0 VAC between drain pump pin 1 and timer contact 13 (T13). What would that reading definitively tell us?

[Samurai Appliance Repair Man]

There are various ways to skin a cat, the best way depends on the specifics of the situation. One of my favorites is to use my jumper wire to bypass the switch.

[Samurai Appliance Repair Man]

i have some questions about the 4th video at 4:00 you did ohms test for the heating element
what live test could you do from the timer instead of ohms? i mean across what points would you check the heating element for 240vac? i tried to find EEPS for voltage test but i didnt

I didn’t see a reference to ohms checking at the location you referenced. Maybe a different video?

But sometimes it’s easier to explain a circuit this way instead of doing a voltage and amp measurement, especially since the point of this lesson (and its title) was to teach about AC Voltage Power Supplies in Electric Dryers.

2.after veryfing both that R contact is ok and the heating element has contiuity when checking the controls you could also do a live test measuring across timer contact BK or even R to timer contact OR and look for 0vac, and if you had read 240vac then youd have known that one of the controls is open.m i correct?

I’m not seeing either of those locations, R or BK, in the fourth video in this lesson.

[Samurai Appliance Repair Man]

so how come in this case of one side of the heating element contacting the casing didnt trip the breaker too?
thats what i dont understand

I answered this my previous reply. You may have missed it:

L1 is NOT contacting the chassis! L1 connects to one side of the broken element. The other side of the element is connected to Ground. The broken element IS the load.

2.what differnce does it make if L1 directly contacts the casing or one end of the element contact the casing? after all the other end of th broken element is still connected to L1

This is basic circuits stuff from Core. What’s it called when one side of the power supply directly contacts the other side of the power supply (L1 to L2 or L1 ro Neutral) or when one side of the power supply directly contacts Ground without a load?

[Samurai Appliance Repair Man]

you didnt disccuse thermostat heater on this webinar but additional heat will cause the bimetal to pop open faster or sooner than if were lower heat,this additional heat will cause the bimetal to reach its temperture limit faster

Correctillia! Even though I didn’t discuss bias heaters, I did discuss bimetals and using that amazing new knowledge, you correctly surmised the function of the bias heater.

[Samurai Appliance Repair Man]

,in this case the thermal fuse that went open wouldent get enoufe heat too since a decreas in in heat will also affect the thermal fuse on the blower housing dosent it?

Can’t say that becauseethat’s exactly what happened in this case. It’s the temperature rating of the device that matters. Remember, when talking about thermal fuses, we have two temperature ratings to think about: holding temperature and function temperature.

2.going by the schematic on the webinar recording if the heat produced wasent sufficient to open the tstat which is rated at 150 degrees while the thermal fuse is rated at 196 degrees
so it stands to reason that the operating tstat will cycle on and off (since heat affect all all the thermostats in the system)plus the fact that they both posintioned on the blower housing,thats what i cant seem to understand.unless you meant that the thermal fuse went open as a resault of a holding tempeture rather than functioning temperture in which case this can definitly occure .m i correct?

Now you’re getting the idea!

.this grounded elemt is not a short condition but since L1 is contacting the metal casing of the element it become a coductore(part of the wire path)

L1 is NOT contacting the chassis! L1 connects to one side of the broken element. The other side of the element is connected to Ground. The broken element IS the load.

and L would somehow touched the the metal casing (for example the line wire or the winding inside the motor come loose or brack and contact the metal housing of the motor or line voltage touch the chasis) and someone touch the any metal part of the machin what would “happen” to him?

If the dryer is wired correctly meaning there’s a continuous Ground all the back to the circuit breaker box, then nothing would happen to someone because if L contacted the chassis, the circuit breaker would trip.

[Samurai Appliance Repair Man]

on your 3th video’s schematic at 2:30 minutes the timer switches BK-BU and BK-V are marked as arrows facing downwards while the other timer switches are bold lines why are these 2 switches marked differently than the rest?

It’s actually the 4th video but I found it. They’re just showing that the contacts at both BU and V switch “down” to BK. Without the arrows, it would be ambiguous to know whether BU could switch up (ie., BU-V) and down (BK-BU). In other words, they’re making it clear that there is not BU-V connection.

2.there is a THERMOSTAT HEATER 5600-8400OHMS on the upper side of the schematic.what is this component and why does the dryer need it?

Pop quiz: You watched the dryer thermal controls webinar recording. Based on what you know about how bimetal switches work, what effect will adding additional heat via the thermostat heater have on causing the bimetal to open?

[Samurai Appliance Repair Man]

i gather that the side which came to contact with the metal casing is L1 which must go through the other thermostats,so how come the operating thermostat or hi limit thermostat didnt function and doing thier job of regulating the heat,thus preventing the thermal fuse going open?

Since element was only operating on half voltage (120 VAC vs. 240 VAC) so what does this do to the heat output of the element? Knowing what you now know about dryer thermal controls, do you think this would be enough heat to cause either of these components to open?

besides why did the other thermal cutoff not go open as well?

There are two thermal fuses in this (and most) dryers, as you learned when you watched the dryer thermal controls webinar recording. Manufacturers like to call them different names but we don’t let that fool us because we’re sharp techs who focus on function, not labels. In this dryer, the two thermal fuses are called “thermal fuse” and “thermal cutoff.” The “thermal fuse” is located on the heater can and has a much higher temperature rating than the “thermal cutoff” which is located on the blower housing. So while the heater did not produce enough watts (heat) at half voltage to open either the “thermal cutoff,” the hi limit, or the operating tstat, it was enough to open the “thermal fuse.”

2.if someone were to touch any metal part of the dryer’s body or the metal casing of the heating element while its on he would be zapped right?

What is the definition of a short? Is this grounded element a short condition?

3.in this case if the dryer were hooked up to a GFCI it would trip once you try to turn it on,m iright?

It’s a 240 VAC supply so you won’t ever see a GFCI on dryers (not yet, anyway). Since you’ve watched the GFCI webinar recording and based on what you learned there about how GFCI’s work, what two current carrying conductors would the GFCI need to monitor to detect a current imbalance? (Hint: Ground is NOT a current carrying conductor; it is a grounding conductor that should only carry current if something goes wrong.)

[Samurai Appliance Repair Man]

this fan is fed by vdc as i seems ,fans job is to cool down stuff ,ventilate,circulat heat etc.. ut i dont understand what afan of any kind has got to do with a washing machin

Right on. Sometimes, we have to be comfortable with not knowing everything about the circuit immediately. Especially if it doesn’t directly pertain to the problem we’re troubleshooting.

Here’s the deal: you’re on a service call, you have the tech sheet/schematic. The schematic is a busy diagram with lots of different circuit on it. When you identify your Load of Interest (LOI), this isolates one specific circuit out of all the other circuits in that diagram. You focus like a laser on that one circuit at this point in the Tango. You need to snatch this pebble: Beware the temptation to flit around like little bird from one unconnected thing to another unconnected thing. Repeat this to yourself when analyzing an electrical problem on a schematic: Everything in sequence. In other words, your next step must be logically connected to the previous one. Similarly, your questions should be logically connected to the teaching in the lesson.

• This reply was modified 2 years, 2 months ago by Samurai Appliance Repair Man.

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