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-   -   No Power to A/C Thermostat (https://www.askmehelpdesk.com/showthread.php?t=354000)

  • May 15, 2009, 06:28 PM
    KenLoh

    Here are some pics of the Air Handler. 1st pic shows the whole layout, just in case you need to point out any particular parts. 2nd pic shows the terminals I tested with the multi-meter. 1-2, 3-4, 5-6, 7-8 all showed 110V. The small panel on the far right, with those wires similar to the thermostat's, show NO power. I tested both inside and outside rows - Zero V. Is this the wire that leads to the thermostat?

    Which one is the transformer? The beige color part directly on the left of the row of thin 24V wires... there is a small "switch" or so it looks like, I tried it but it doesn't seem like it switches anything. Perhaps it's just a release to remove the beige plastic casing? There's a closeup pic of it in the 3rd pic.

    Thanks for the help.


    http://img196.imageshack.us/img196/5...rhandler01.jpg

    http://img196.imageshack.us/img196/5...rhandler02.jpg

    http://img196.imageshack.us/img196/1...rhandler03.jpg
  • May 15, 2009, 06:32 PM
    KenLoh

    OOOPS! I accidentally made a repost somehow. Can a moderator please remove the above post to avoid confusion?

    Sorry, and Thanks!
  • May 15, 2009, 06:37 PM
    KISS

    This thing is a fuse:

    http://www.geocities.com/SiliconValley/2072/fuse.gif

    This is a DPDT relay. http://www.techitoutuk.com/knowledge.../relaydpdt.gif The object you labeled.

    Who knows what it's function is, but two terminals, like the ones nearest to RL1 in the picture are the coil. When you apply power to the coil, the common contacts move from the unpowered state (Normally closed) to the powered state (Normally open).

    Right now, that device is out of the picture.

    You need to concentrate on locating the thermostat wires and following particularly the red one.
  • May 15, 2009, 06:53 PM
    KenLoh
    Quote:

    Originally Posted by KeepItSimpleStupid View Post
    Right now, that device is out of the picture.

    You need to concentrate on locating the thermostat wires and following particularly the red one.

    So, the condenser is out.
    Now you are saying the Relay is out.
    You think there is something wrong with the wire running from the transformer to the thermostat?
    What about the transformer? How should I test that now, without being able to activate the Relay/contacts?
  • May 15, 2009, 06:54 PM
    KISS
    The thing you labeled as a "switch "can be either a switch, fuseholder or breaker. I think it's one of the latter two.

    Now that I can clearly see the laminations (stacked pieces of grey/black metal), the white section is attached to the transformer. Because your "switch" is enclosed in the plastic case, it is likely on the primary side of the transformer. This isn't guaranteed.

    Note, it has markings like 24 VAC and probably sec. or secondary. And 120 VAC pri. Or primary.
  • May 15, 2009, 07:02 PM
    KISS
    Look at how mechanically sound, the tin read and the thin blue connections are.

    There is green, brown and black wrapped around the thermostat brown jacket. Look at that cable. Follow the red and blue wires. Remove the wirenut, but not the connection to the red wire. Measure between the red and blue in that cable.

    Green is normally used for the fan, but it seems unconnected. I'm assuming blue goes to the C wire of the thermostat.
  • May 15, 2009, 07:23 PM
    KenLoh
    Quote:

    Originally Posted by KeepItSimpleStupid View Post
    Look at how mechanically sound, the tin read and the thin blue connections are.

    There is green, brown and black wrapped around the thermostat brown jacket. Look at that cable. Follow the red and blue wires. Remove the wirenut, but not the connection to the red wire. Measure between the red and blue in that cable.

    Green is normally used for the fan, but it seems unconnected. I'm assuming blue goes to the C wire of the thermostat.

    I looked at the wires, they all look good, and secured. However, I can't run it's length to the wall thermostat, it's behind walls! When I test them on the meter, there is no power to any of the 24V wires.

    Yes, Blue is on C at the thermostat end. NO power at that end either. I also did connect Red and Green, no response to fan.

    Hang on... I opened the beige box in the transformer and took some pics, looks like a fuse. BRB...
  • May 15, 2009, 07:40 PM
    KenLoh
    Here are pics of that beige plastic cover removed from the transformer. It looks like a fuse, I can't open that black casing up, didn't want to try too hard and break the solder on those wires. I did a connectivity test on the meter on F1 and F2 and it was positive, needle went all the way to the right of the scale. (Sorry, not sure how to read the units for this test, told you I'm an amateur! :D). Anyway, so does that mean the fuse is good?


    http://img268.imageshack.us/img268/7...rmerfuse01.jpg

    http://img268.imageshack.us/img268/2...rmerfuse02.jpg

    http://img268.imageshack.us/img268/4...rmerfuse03.jpg
  • May 15, 2009, 08:30 PM
    KISS
    Yep, circuit breaker: http://www.onlinecomponents.com/prod.../mf-PB/w28.pdf

    The 32 V and the lines mean 32 VDC so it's on the low voltage side.
  • May 15, 2009, 09:25 PM
    KISS
    Measure the voltage across the terminals F1 and F2?
  • May 15, 2009, 09:31 PM
    KenLoh
    Quote:

    Originally Posted by KeepItSimpleStupid View Post
    Yep, circuit breaker: http://www.onlinecomponents.com/prod.../mf-PB/w28.pdf

    The 32 V and the lines mean 32 VDC so it's on the low voltage side.

    So, is this circuit breaker good and can be put out of the picture here? Did I test it correctly to determine that it's good, if not, how should I test it?

    Can I assume that the problem lies somewhere between this circuit breaker and the row of 24V terminals R. W. G. C ?
  • May 15, 2009, 09:37 PM
    KISS
    OK. The red coil of the thick wire should be the low voltage winding. If you can find the two ends, you should have 24 VAC there at all times.

    That should be white braid to blue. (24 VAC)

    Now look at Blue to white braid + CB + Yellow.
    ... (C)... (#1)... (#2)

    What is C to #1?
    What is C to #2

    What is the voltage across F1 and F2?

    Circuit breaker may still be in the picture, may not. The above tests will help.
  • May 15, 2009, 09:38 PM
    KenLoh
    Quote:

    Originally Posted by KeepItSimpleStupid View Post
    Measure the voltage across the terminals F1 and F2?

    No I did not, when I had that opened up, I didn't turn on the power.
    I just did the connectivity test to see if the fuse was good.
    Should I? I can do it if it will prove something to help with the troubleshoot.
  • May 15, 2009, 09:46 PM
    KISS

    Yep, do these with the power on:

    Refer to post #32.

    What is voltage from C to #1?
    What is voltage from C to #2

    What is the voltage across F1 and F2?
  • May 15, 2009, 09:48 PM
    KenLoh
    Quote:

    Originally Posted by KeepItSimpleStupid View Post
    OK. The red coil of the thick wire should be the low voltage winding. If you can find the two ends, you should have 24 VAC there at all times.

    That should be white braid to blue. (24 VAC)

    Now look at Blue to white braid + CB + Yellow.
    .....................(C)..............(#1)........ ..........(#2)

    What is C to #1?
    What is C to #2

    What is the voltage across F1 and F2?

    Circuit breaker may still be in the picture, may not. The above tests will help.

    Pardon my dumbness... I'm trying to understand your instructions. I'm completely lost.

    What do you mean by "red coil of the thick wire"?
    What is "white braid to blue"
    What is "Blue to white braid + CB + Yellow"
    What is "C to #1"
    What is "C to #2"
  • May 15, 2009, 10:01 PM
    KISS

    Here is the post:

    OK. The red coil of the thick wire should be the low voltage winding. If you can find the two ends, you should have 24 VAC there at all times.

    That should be white braid to blue. (24 VAC) I can see these wires with the coil in the middle

    This was my way of drawing a circuit. There is a blue that connects to a red coil and then a white braided wire and then to a circuit breaker and then to a yellow wire. The terminals are paths along it's way

    Now look at Blue to white braid + CB + Yellow.
    ... (C)... (#1).. . (#2)

    What is voltage fromC to #1?
    What is the voltage fromC to #2

    I added the italics.

    Point C is the blue wire. Point #1 is the white braid and point #2 is the yellow wire.

    Circuit goes like Blue (C) to transformer to a (#1) white braded wire to a circuit breaker to a (#3) yellow wire.
  • May 15, 2009, 10:08 PM
    KenLoh

    Ok, I think I got you now. The red coil is the Actual Coil (literally) inside the opened white fuse cover, right? So you want me to measure across that short braided white wire, blue wire, yellow wire, etc... right?
    Which are you referring to as #1 and #2?

    I'm going out to do what I understand right now, and will be back with some numbers.
  • May 15, 2009, 10:30 PM
    KenLoh

    Here you go:

    Blue - Braided White - 26V
    Blue - Yellow - 26V
    Yellow - Braided White - Nothing

    I also tested the row of R. W. G. C terminals...
    R-C, R-G, R-W... they all showed the same 26V
  • May 16, 2009, 12:34 AM
    KenLoh
    Quote:

    Originally Posted by KenLoh View Post
    Here you go:

    Blue - Braided White - 26V
    Blue - Yellow - 26V
    Yellow - Braided White - Nothing

    I also tested the row of R. W. G. C terminals...
    R-C, R-G, R-W....they all showed the same 26V

    Refer to pics below for a clearer description. Hope I understood you correctly, KeepItSimpleStupid. So, are we there yet? What's the verdict? Wife wants me to call someone in tomorrow, but I've come this far... really don't want to give up at this point. The pressure is on, as Saturday is the last work day, won't be able to get any parts or anyone in on Sunday. And it's getting uncomfortably warm in the house!

    http://img194.imageshack.us/img194/7...rfusevac01.jpg

    http://img194.imageshack.us/img194/5...rfusevac02.jpg

    http://img194.imageshack.us/img194/8...rfusevac03.jpg
  • May 16, 2009, 07:23 AM
    Joshdta

    Do you get power on both lines after you reset the trip out switch?

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