compressor motor windings

[thepunk]

When testing voltage on motor windings, say from run to common or start to common would the meter have the same results as reading a switch.  If the winding is open would the meter show 120 volts or 0.  Or would the meter just read 120 either way whether the winding is open or closed or vice a versa.

[Repair-man]

Motor windings are tested for resistance, not live voltage. You use the OHM meter to read between each of the  terminals. The resistance values are given in the manual.


If there is voltage going to the compressor and it does not run, it or the  relay is bad. You are really needing to study up on Basic electricity before going further.

Link: http://appliancejunk.com/forums/index.php?action=downloads;sa=view;id=60

[thepunk]

I realize that ohm tests are done on motor windings, but just for the sake of it, if a switch when open reads 120 volts, then would a winding not do the same.  In another words, would the voltage readings of a meter read the same  in all conditions when testing across contact points between a switch or a winding. 

[Repair-man]

If a switch is open you will read voltage.

If a switch is closed you will not read voltage.

If a motor winding is open, you will  read voltage.


If a motor winding is closed, you will still read voltage.

A switch is not the same as a motor.


Look at it this way, sparky...if a light bulb burns out, you will still see 120 volts going to it, right?

[thepunk]

  Cool, actually that is what I was thinking.  Inductance, reactance.  Different than a switch.  Thanks!  How do you donate to this site, other than the dumb questions.

[JWWebster]

Start run and common will read different ohms. Between start and common is a coil and between run and common is another coil. Between run pin and start pin would give you the value of both start and run combined. Of course any pin that has a reading to ground means a bad compressor. Just thought I would throw that in. Has nothing to do with voltage checks.

[thepunk]

I know I am asking a lot, but I kind of find appliances interesting, actually I do some minor repairs, for family and friends that is why i ask.  But anyhow, on a reversing valve selonoid, window unit AC heatpump, if there is voltage 120 at the reversing valve, does that normally mean that the selonoid is bad if the unit is blowing cold air in heating mode.  Or can the switch or thermostat be stuck.  Thanks. Enquiring minds want to know.

[Repair-man]

Try posting this as a new topic in the HVAC forum and you'll get a  esponse.

[thepunk]

Where is HVAC repair at.  I don't see it on your forum.  Or is it a joke, if so I am up for a good laugh!

[thepunk]

So sorry!  I found the HVAC forum.  Thanks!  I didn't know you had other forums here, I had to go to the Home page then to the HVAC forum.  Thanks a bunch!

[thepunk]

So, sorry!  Again, I thought if I went over some of your service manuals it might help in my understanding of voltage tests, I noticed that the SMFHAcks page comes up over the download service manuals page, I don't know if it is a virus Adware or what ever when I go to download those help manuals, but anyway if I click off the SMF HAcks page the service manuals page will show and then I can download fron there.  I haven't noticed this problem before on any other sites, so I don't know if SMFHacks is affilated with you or not, I believe they are, it was mentioned before.  Thanks a Bunch.  Merry Christmas to you all!

[JWWebster]

Dude that is something within your PC giving you that website.

[JWWebster]

That would mean a bad solenoid. To verify take it off and check it for continuity. The only time the valve could be stuck is if a shotty install ruined it to begin with.

[thepunk]

Enquiring minds want to know.  Well since you answered that question, I have another! In the heating mode, and the heat pump window ac unit is suppose to blow warm air but is blowing cold and  If the selonoid, reversing valve has 0 volts across it and the defrost control is measuring 120 volts across the contacts, would the selonoid be bad or the defrost control.  I mean isn't the defrost control just like a switch, and if so wouldn't the meter read 120 volts if the contacts are open.