Susan Brown

[Susan Brown]

This question is designed to get you to think through the terminology. The fact that it is a “live circuit” means that voltage is applied, but does not necessarily indicate that current is flowing. An “NO” switch being “in its normal state” means that it is open. So, we are measuring across an open switch and would expect to measure the source voltage.

[Susan Brown]

Do you remember what we taught you about current in a series circuit?

It is the same at any point in the circuit. The electrons are all moving or none of them are moving. And if they are moving, they move at the same rate. This is where it is NOT helpful to think of water flow. Better to think of a tightly packed toy train track loop with no gaps between the train cars. If you push one they all move at the same rate.

So you can measure anywhere on the circuit, from wherever you can get the clamp around the wire.

[Susan Brown]

*Power*, which is current AND voltage. The bottom line with loads is power, but since we don’t measure watts, we use amps and/or voltage drop as proxy measurements.

[Susan Brown]

Hi John,
It opens as a pop-up – I wonder if you have a popup blocker?

Click here for the image. Does it open?

I’ll embed it here, if that helps

• This reply was modified 10 months, 2 weeks ago by Susan Brown.
• This reply was modified 10 months, 2 weeks ago by Susan Brown.

[Susan Brown]

Our answer is basically describing the logical flow of thought – we don’t mean for it to imply that you shouldn’t look at the schematic and determine where/how you’re going to do your measurements.

[Susan Brown]

Hi John,

The answer we’re looking for is, “Follow the line cord inside the machine, measuring voltage as you go, to find where you’re losing the voltage”

Because when there is absolutely nothing going on – no lights or responses to key presses – then you are losing voltage somewhere between the outlet and the controls (the board, assuming it has one).

[Susan Brown]

We don’t give the answer in a neat and tidy way – what we want is for you to apply what we teach about inputs and outputs to this question.

Inputs to a control board would be information that the board can then make “decisions” about. So, sensor data or a feedback signal, for example.

Outputs from a control board are generally things that will be used by the loads or a sub-board, like power supplies.

If you have trouble identifying which of our answer choices fall into which category, send me and email and we can go over that privately (so we don’t give the answers away here).

[Susan Brown]

Thanks, you too!

[Susan Brown]

You can continue on, since we grade those pretty quickly (same day, usually) and you can then use your second attempt. It’s just best not to go *too* far until you’ve passed it, just in case.

[Susan Brown]

You’ll see at least one like that in Module 4 (unit 2).

[Susan Brown]

No problem! You’ll see it mentioned again in the Troubleshooting module.

[Susan Brown]

Hi John,

The question is, ” What would happen to the evaporator coil if the defrost heater failed open?” There is no “to” before “open”. An important difference!

For a heater to “fail open” means that it is electrically open somehow, and electrons are not able to move through it. Often the heater material has a break in it.

Make more sense now?

[Susan Brown]

If the entire appliance is unresponsive (no lights or anything), the very first thing you check is to see if 120v is present at the wall outlet.

[Susan Brown]

Good! Glad to help.

[Susan Brown]

Because L1 and L2 are 180 degrees out of phase with each other. When one is +120v, the other is -120v. We first describe this in Mod 4, unit 6, then I talk about it some more in that video in Mod 4 unit 9.

[Author]

Posts