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Thread: No Continuity at Compressor Terminals

  1. #1
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    No Continuity at Compressor Terminals

    Good morning everyone. My trainer and I got called to two Kingcool Condensers down at a pair of newer two story townhouses that were not getting any cooling. Everyone of the units here (there are 4) in the complex we had worked on due to various issues all related to poor installs. The condenser fan was running, pressures were equal across the suction and liquid line at 227 psig (410a refrigerant) same on both units pretty much.

    I ended up pulling the paneling off so that I could expose the compressor. Run caps were both fine. I followed the 240v power to the terminal block on the compressor. There are 3 terminals. Its a scroll compressor. No continuity between any of the terminals. Nothing between the start and run, run and common, common and start.

    I have two part question here, one involving my gauge manifold. When I hooked up as usual low side blue hose to suction valve and red hose high side to liquid line, I would get 0 psig on my suction side and 227 on the high side. I knew there to be pressure on the suction side as when i went to put my hose on, I heard the refrigerant escape. I switched them, high side hose to low side and low side hose to high side and then I was able to get my low side to read pressure. Why is this?

    Question 2, what would cause Open line on my compressor terminals run, start and common. Like no continuity at all on both compressors in each of the condensers. Again, I am a first year apprentice. My trainer believes the compressor to be burned out. I believe him, there is obviously something wrong to have no continuity. I am answer seeker. Thanks again.

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    No Continuity at Compressor Terminals

    Sorry had to read your post quick...hopefully this helps

    Compressor probably pumped down so very little pressure in suction side

    Terminals open AT COMPRESSOR mean open windings = bad compressor

    Internal overload can also open circuits so make sure compressor is cool before ohm testing
    "I think Quantum tunneling would work great... "

    "Call a technician for God's sake. Or we'll see you on the news or the Dark Side of the Moon."

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  4. #3
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    Quote Originally Posted by Dwayne2021 View Post
    Good morning everyone. My trainer and I got called to two Kingcool Condensers down at a pair of newer two story townhouses that were not getting any cooling. Everyone of the units here (there are 4) in the complex we had worked on due to various issues all related to poor installs. The condenser fan was running, pressures were equal across the suction and liquid line at 227 psig (410a refrigerant) same on both units pretty much.

    I ended up pulling the paneling off so that I could expose the compressor. Run caps were both fine. I followed the 240v power to the terminal block on the compressor. There are 3 terminals. Its a scroll compressor. No continuity between any of the terminals. Nothing between the start and run, run and common, common and start.

    I have two part question here, one involving my gauge manifold. When I hooked up as usual low side blue hose to suction valve and red hose high side to liquid line, I would get 0 psig on my suction side and 227 on the high side. I knew there to be pressure on the suction side as when i went to put my hose on, I heard the refrigerant escape. I switched them, high side hose to low side and low side hose to high side and then I was able to get my low side to read pressure. Why is this?

    Question 2, what would cause Open line on my compressor terminals run, start and common. Like no continuity at all on both compressors in each of the condensers. Again, I am a first year apprentice. My trainer believes the compressor to be burned out. I believe him, there is obviously something wrong to have no continuity. I am answer seeker. Thanks again.
    Kind of rare to find a compressor like that. As Jayman said make sure the compressor is cool. I always pull fan a put my hand on top of the compressor. if it's warm at all then it certainly has had continuity in the last few hours and most like is overheated internally and has OL itself. When the compressor is in OL it will not be able to run. I turn on the AC with gauges connected and let the condenser fan run, that in itself will help cool the compressor but if you got some water to run on it that will certainly help.

    But listen cause most likely when it cools off enough to run it'll just grunt for a couple seconds and stop.

    Double-check capacitor and add a hard start once OL closes....

    If comp never shows continuity its bad....

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    Quote Originally Posted by jacob-k View Post
    Kind of rare to find a compressor like that. As Jayman said make sure the compressor is cool. I always pull fan a put my hand on top of the compressor. if it's warm at all then it certainly has had continuity in the last few hours and most like is overheated internally and has OL itself. When the compressor is in OL it will not be able to run. I turn on the AC with gauges connected and let the condenser fan run, that in itself will help cool the compressor but if you got some water to run on it that will certainly help.

    But listen cause most likely when it cools off enough to run it'll just grunt for a couple seconds and stop.

    Double-check capacitor and add a hard start once OL closes....

    If comp never shows continuity its bad....
    Hi guys, so yes the compressor was cold as a cucumber that has sat in the fridge lol

  7. #5
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    Did you check for continuity to ground on those terminals. When I have seen open windings like that there is usually a short to ground. More than likely what happened is where the windings attach to the IOL have broke off. If the IOL is open you should have a reading between S & R.

    As to your gauges it may have to do with the core depressor in your hose, or you may have just not had it tight enough to depress the core.

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    Check ohms C-S, C-R, and R-S. If all 3 are OL on a cold compressor, then there's an internal electrical failure. Check C-ground, R-ground, S-ground to see if the windings became grounded out. Getting on OL is what you want. IF you get any sort of number, the windings touched the case of the compressor and blew it up.

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    Quote Originally Posted by YOUNG FROSTY View Post
    Check ohms C-S, C-R, and R-S. If all 3 are OL on a cold compressor, then there's an internal electrical failure. Check C-ground, R-ground, S-ground to see if the windings became grounded out. Getting on OL is what you want. IF you get any sort of number, the windings touched the case of the compressor and blew it up.
    awesome. we are going back tomorrow. The only thing that we didn't check was the continuity to ground on the terminals. Thanki you guys a lot for all the help. I am just loving this!

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    Quote Originally Posted by Dwayne2021 View Post
    When I hooked up as usual low side blue hose to suction valve and red hose high side to liquid line, I would get 0 psig on my suction side and 227 on the high side. I knew there to be pressure on the suction side as when i went to put my hose on, I heard the refrigerant escape. I switched them, high side hose to low side and low side hose to high side and then I was able to get my low side to read pressure. Why is this?
    I note about this, I have JB Kobra low loss hoses and as I attach them to service valves the first thing they do is depress the valve core, keep screwing and the gasket seals, finally when fully attached the hose valve opens. I have had this same thing happen, you hear the short hiss from the system then the hose gasket seals and you believe the connection is made but there is no activity on the gauges, give another 1/8 turn and BOOM all is well.
    As a side note, the only reason your “hose” would be reading zero psi would be if there was no refrigerant in the line you are connecting to or if you didn’t purge the air out of your gauges and hoses and then didn’t make the connection. This is a big no no, if you are using gauges with hoses you must ALWAYS purge them otherwise you could introduce air into the system. If you are using probes then that is a different story. To purge low loss hoses you need to hook one hose up to a tank and then use a valve on the other hose/hoses. Best to save yourself lots of time and trouble and purchase some Bluetooth probes.

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    Quote Originally Posted by BNME8EZ View Post
    Did you check for continuity to ground on those terminals. When I have seen open windings like that there is usually a short to ground. More than likely what happened is where the windings attach to the IOL have broke off. If the IOL is open you should have a reading between S & R.

    As to your gauges it may have to do with the core depressor in your hose, or you may have just not had it tight enough to depress the core.
    What is the IOL? On my terminal, different unit from the one above, i am getting continuity between run and start, but no continuity between common and start and common and run. Also ol on all terminals to ground

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    IOL- internal over load

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    227 PSI on 410A means the system is at about 80 degrees.
    With your gauge needle on 227 psi, follow the needle down to temp in F degrees, it lands on about 80 degrees.

    If you put your gauges on a bottle of gas that has been sitting at 80 degrees you would see about 227 psi.
    Refrigerant pressures translate to temp and are a very accurate thermometer.

    I would guess that your low side hose did not depress the Schrader core.

    A word of caution....years ago I was trying to start a comp that was simply humming,
    The cover was removed from the terminal block. When power applied the internal windings shorted and blew out the term block.

    Gas and oil shot out immediately for a distance of about 10', I was lucky not to have my head close to this blow out.
    And this was R-22, much lower pressure than what you have there.

    It did hit the homeowner's young fruit tree, he was not happy.

    The unit was on a concrete pad that also had a 30' TV tower 2' away.
    The line set was buried under ground for about 4'...great ground rod BTW.
    It was a rare Christmas eve lighting storm that found that tower.
    I was able to convince the insurance company that that was the cause.

    So be careful around the term block....things can happen.

    Does the oil smell burned? You mentioned bad installation.
    Would do an acid test on the gas/oil.
    If nasty/bad, you do not want that gas/oil in your gauges, I would flush them with nitrogen.

    Just for training you could put a megohmmeter on the windings, it may show you more than a simple ohmmeter.

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    Quote Originally Posted by Dwayne2021 View Post
    What is the IOL? On my terminal, different unit from the one above, i am getting continuity between run and start, but no continuity between common and start and common and run. Also ol on all terminals to ground
    IOL as said is Internal Over Load. It is a thermostat that senses winding temperatures. In a compressor the C terminal is connected on one terminal of the IOL. The windings have one end connected to the other end of the IOL. The other end of the windings are connected to the R & S terminals.

    The next time you have a schematic in hand look at the compressor drawling, it will show how the IOL ties in.

    If you have continuity from R-S then the IOL is open.

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    The dates on this thread not making sense.

    So you've been working on this system for one year - or left it for one year and just got back to it?

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    You sure this unit is not 3 phase?

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    Quote Originally Posted by szw21 View Post
    The dates on this thread not making sense.

    So you've been working on this system for one year - or left it for one year and just got back to it?
    Come on man the man is busy ! 😆

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    Quote Originally Posted by TechmanTerry View Post
    You sure this unit is not 3 phase?
    No it 240 volt on a townhouse. Yes, its funny that i googled my issue and found my thread from last year. The run cap was also good. The compressor was cd so it hasnt run for quite some time.

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    Quote Originally Posted by Dwayne2021 View Post
    No it 240 volt on a townhouse. Yes, its funny that i googled my issue and found my thread from last year. The run cap was also good. The compressor was cd so it hasnt run for quite some time.
    What’s “CD”?

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  25. #18
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    C(OL)D maybe ?

    Quote Originally Posted by pecmsg View Post
    What’s “CD”?
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

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    Considered Dead

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    Sounds DRT…(dead right there). Internal overload could have failed open.

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