Sam Brown

[Sam Brown]

When you make a voltage test, you need to ensure that the circuit you are testing is supplied with power. Otherwise, it’s not a live test.

So yes, in your drain pump example, you would want to active a drain cycle or activate the drain pump in test mode.

[Sam Brown]

If you pay attention to the name of each thermal control and think about their function, you’ll get an idea of its intended purpose in the circuit.

The operating thermostat, as its name suggests, opens and closes during normal operation to moderate temperature. It’s the intended way for temperature to be regulated in a normally functioning dryer. The hi-limit, on the other hand, is there to put an upper limit on how hot the machine can get during a cycle for safety reasons. So one is expected to open and close during operation and the other is not.

The thermal cut-off is also there for safety, either as the “last line of defense”, which would be when it goes open at its functioning temperature, or as an indicator that there is a chronic problem with the dryer, which would be when it goes open due to cumulative hours at its holding temperature.

As for the temperature selector, it’s just an infinite switch, like the kind you use to control the stovetop burners of a range. If you look at the circuit with that in mind, you should see how the temperature selector allows the user to adjust the drying temperature.

[Sam Brown]

Hi. I got this one wrong. I chose 8.49 VAC. I have an 18v battery from my cordless drill. I put my meter on it. When testing with the DC setting, I get 17.4 volts. When I switch the leads I get -17.4v.

When I switch the meter to the AC setting, I get 38.3, and if I swap the leads, the negative sign pops up, and it shows 0 on the meter. Please advise.

That question is assuming you’re doing this measurement on a standard copper-top battery, like a Duracell. If you measure AC across a battery like that, you will read 0.

A battery for a drill is going to be different and more complex. Those contain circuitry with load-sensing capabilities, and that circuitry can cause weird AC readings like what you’re describing.

[Sam Brown]

The video in module 7 unit 4 covers this very directly — is that the one you’ve been reviewing? Once of the first slides covers the path the spark current takes.

[Sam Brown]

but i dont get why arent they old plain bimetals.

That’s the thing — they are plain old bimetals. A bimetal is a bimetal — they all work the same way. These bimetals just have itty bitty heaters attached to them so that, in cycles when those bias heaters are activated, the bimetal goes open. This is desirable on low heat cycles, like the delicates cycle. But these bimetals will also open in response to heat from the main heater coils, as we discussed in the video.

These aren’t weird and different technology — just a clever adaptation of a regular old bimetal and a regular old heating element.

[Sam Brown]

The table shown was for illustrative purposes — to show the difference between functioning and holding temperatures. For whatever reason, the manufacturers did not include temperatures in certain spots. We work with the specs we’re given.

The cycling thermostat is only one part of the equation. A number of other issues could cause a thermal fuse to open, such as a grounded heating element or clogged vent. Any situation that causes excessive heat buildup can cause or contribute to a thermal fuse opening.

[Sam Brown]

We didn’t cover those because that wasn’t the focus of the lesson. Again, be careful not to get led off on rabbit trails. These are real-world schematics, so they contain lots of different elements, and we’re not going to cover every single thing shown on a schematic in a single lesson.

However, I will say this: the bias heater’s function is pretty self-explanatory when you consider a) how bimetals work, and b) during which cycles the bias heater is activated (see the timer chart). You should be able to figure out for yourself the purpose of the bias heater with the information shown on the tech sheet.

[Sam Brown]

Yep, a grounded heating element or any other condition that would cause excessive heat buildup — a clogged vent, for example. That cutoff will go open and shut off power to the motor in those cases, rendering the dryer inoperable until the problem is solved.

[Sam Brown]

Precisely — they’re two different bimetals positioned at different points in the dryer. If the control inlet bimetal opens, you effectively get a lower heat setting, with only one of the heater coils energized. In certain cycles, lower heat is desirable.

on the other hand iv noticed another thermo hi limit to the left of the start switch is it a thermal fuse or a hi-limit bimetal? could a dryer have 2 hi limits? im a little confused

The machine can be designed to have as many thermal controls as the engineers think are necessary. Why do you think they would put one in the motor circuit?

[Sam Brown]

1.on your last video lesson at 1:40 the timer chart on auto dry coloumn there is a T-F (timer motor)timer contatct that is closed during auto dry you havent talked about and i also tried to find this on the schematic and didnt, how does this T-F CONTATCT come into play ?it definitly has something to do with the timer motor

You said you can’t find the F contact on the schematic, which is correct — it’s not present. So that T-F row on the timing chart is nonfunctional to us. The auto-dry function works on the schematic as shown. These timing charts often get used with multiple schematics, and there’s probably a different one that does have an F contact. But ours doesn’t, so we can safely ignore it.

As for your other two questions about the two different controls in the heating circuit: why do you think there are two bimetals in the circuit? What happens to the circuit if the control inlet bimetal opens and the drum outlet bimetal doesn’t?

[Sam Brown]

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

He could have done a voltage test from the same points he did that ohms test, but in this case, because of the physical configuration of the connectors, it was easier to do an ohms test. He had to stick his hand way back past a bunch of connectors to get a probe on 1M, and if the machine had been live, there would have been a significant risk of him getting a shock. The physical layout of the machine is important to consider when identifying what test you want to use.

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?

Yes, he could have done a live measurement there, and you’re correct on the expected results. But again, this is a matter of practicality. He already had the machine unplugged for the previous test, so it was quicker and easier to do another ohms measurement. And while an ohms test can lie when it shows something in spec, if it shows that something is out of spec (or open, in this case), that is definitive proof that that component has failed. In other words, something that checks good on ohms can still be bad, but something that checks bad on ohms is definitely bad.

• This reply was modified 2 years, 3 months ago by Susan Brown. Reason: typo

[Sam Brown]

Yep, you got it. And here’s the thing: all centrifugal switches function the same way, even if they look slightly different or have slightly different ways of accomplishing this. You have weights that get flung out by centrifugal force once the motor begins to spin, making the contacts, and then you have a spring that pulls the weights back into place when the motor winds down. So don’t get distracted by centrifugal switches that look a little different. Focus on function over form.

To address your other questions, centrifugal switches these days are almost always built into the motor and not replaceable as a separate part. You typically only find them separate in some much older models. And they’re very reliable parts, so not a common fail item.

[Sam Brown]

Before we get to any of those questions, let’s make sure we’ve got our basics covered. What function does the centrifugal switch serve electrically?

[Sam Brown]

You’re correct that the reference to a link in the description is outdated. No such link exists anymore.

But the part he’s referencing would be WPW10006355. It’s not an industry standard mode shifter — it’s specific to Whirlpool’s platform.

And that sounds like a fun welding project! I’m excited to see the results.

[Sam Brown]

The arc is how far the agitator turns per stroke. On a fast cycle, as it says, it spins 360 degrees — a full rotation. At slower speeds, you only get partial rotations per stroke.

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