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Cold control thermostats and switches in appliance circuits

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thepunk:
My question applies to most appliances.  When doing voltage tests on switches, thermostats and cold controls in refrigerators, can you test voltage across the switch contacts.  I have been checking out some information about circuit testing and some info indicates that you can test a switch in a series circuit, such as a cold control and if it is closed you will get a reading of 0 volts, if it is open you will get a reading of 120 volts.  A voltmeter in series with a switch!!  I always thought you measured voltage from one side of the contact to common on the other side of the line closer to the negative side of line out.  If a voltmeter is in series with the contacts of the switch, thermostat or control, how can it get a reading, unless the voltmeter acts as an amp meter, or maybe the voltmeter just takes the path of least resistance, can anyone explain this.

whirlpooltech:

--- Quote ---If a voltmeter is in series with the contacts of the switch, thermostat or control, how can it get a reading, unless the voltmeter acts as an amp meter, or maybe the voltmeter just takes the path of least resistance, can anyone explain this.
--- End quote ---

When your taking a voltage reading across the contact of a switch your meter is in parallel with the switch, not in series.

So when the switch is closed you do not get a voltage reading because the probes of your meter are on the same line.

whirlpooltech:
Here are some self study manuals that you may also find helpful.

http://appliancejunk.com/forums/index.php?action=downloads;cat=23

thepunk:
I never thought of the meter being in paralel with the switch, but I haven't done a lot of voltage tests, mostly amp and ohms.  that is really helpfull, Thanks!  I tried to access your link about diagnosing appliances, but the link takes me to a hacks page, is there a missing link somewhere.  Thanks for info.

AJ:
Link works ok for me.

You can also go to the "Helpful Links" box on the left side.
Click on "Manual Index" and then towards the bottom of the "Downloads" page you will see the "Self Study Appliance Repair Manuals" link.

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