AC troubles

Discussion in 'General RVing' started by Mark in Austin, May 21, 2005.

  1. Mark in Austin

    Mark in Austin New Member

    Hello-
    We bought a used 1996 Dutchman trailer with a Duo-Therm AC unit. It has a Magnetek Power Plus panel box.
    Before we bought it, we tried the AC and it worked fine. Once we got it towed to its new site (property were we are going to build a house/shop)I immediately tried it out using 110V 15 amp circuit (30amp circuit was not installed yet). Lights and refrig worked, so I started AC. AC started, then popped the breaker.
    Installed new 30amp circuit, lights and refrig fine, AC does nothing. Any ideas? Repairman is a bit expensive for me right now, would like to fix it myself if possible.

    Mark in Austin, TX
     
  2. Gary B

    Gary B Senior Member

    AC troubles

    Hi Mark, as you now know running the AC on 15 amps is a no no, the AC by its self will draw 15 to 17 amps on start up and will draw 7 /8 amps on steady running. You say you installed a 30 amp cicuit by this do you mean a 30 amp plug-in to match your shore power cord or just a 30 amp circuit breaker? If it just a 30 amp circuit breaker that won't cut it, you need a full 30 amp service. Check all the circuit breakers in the trailer control panel / trip them one at a time and reset them and try after that. The air conditioner will not reset after it trips a CB for a min. of 7 minutes. Good luck.
    :) :laugh: :cool: :bleh: ;) :approve:
     
  3. Kirk

    Kirk Senior Member

    AC troubles

    As Gary states, there is no way that a 15A circuit will carry your air conditioner, and if the breaker did not trip, the motor would be damaged so that was a good thing. Your air conditioner has a run current of about 13A and the start current is probably twice that.

    I will assume that you now have a properly wired outlet supplied by wire of the proper gage? If so, did you check the circuit brakers in the power distribution panel of the RV to be sure that none is tripped? When you check them, you need to throw them to the open position and back closed. If one trips, the handle may move very little and you must fully open it in order to reset it, before you close it again. If you did not do that when you found one tripped, it is still not closed. Have you checked the voltage inside of the RV to see what it is? It should be no less than 108V and not more than 130V.
     
  4. Mark in Austin

    Mark in Austin New Member

    AC troubles

    Thanks to both who replied.
    I had installed a new 30amp breaker in the system, wired with 10da copper, and am using a commercial extension cord. I tripped and reset all the breakersa a couple of times already. When I set the thermostat to "Cool", nothing at all happens.

    When I (fo0lishly) tried to start it on 15amp, it started then the breaker popped and it shut down.
    I will check the voltage next, but everything else works (except the micrwave, but it appears dead).

    Mark
     
  5. Kirk

    Kirk Senior Member

    AC troubles

    There are a couple of hints here if we can figure them out. You say that you are using a commercial grade extension cord, does that mean that you have a 30A cord with the same 30A plugs at each end as your RV's cord and an outlet of that type, or is this one of the very heavy cords that is designed to plug into a common house outlet with the 15A rating? If it is the latter, it isn't intended to supply 30A as the max. rating of any outlet of that design is 20A and those have the hot leg pin that is T shaped since 20A power cords have the same pin turned 90 degrees.

    Are you sure that you have any 120V-ac power in your RV? Your lights work from 12V-dc power and will work just fine with not outside power as long as the battery is charged, and that would be quite some time. The only item that you have mentioned so far that uses 120V-ac as well as the air conditioner is the microwave? Have you tried to plug something into the other outlets and seen it work? It is my guess at this point that you have no 120V-ac power and are using lights from the battery. If your RV has a refirgerator that will select it's power source automatically, check to see if it is on propane or on AC power? I am betting that it is on propane due to a lack of AC power.
     
  6. Mark in Austin

    Mark in Austin New Member

    AC troubles

    Hello-
    My computer is working fine. This email is done on the computer running on AC. The refrig is AC, and my portable fan is AC. They are all working fine.

    The cord is a 30amp RV extension cord, big black thing with roundish 3-pin connectors at both ends.

    Mark
     
  7. "007"

    "007" New Member

    AC troubles

    Mark, you may have a selector switch used to select your micro or ac not both at same time, if its set in center neither one will work. --"007"
     
  8. Kirk

    Kirk Senior Member

    AC troubles

    Well, I guess that I lost that bet! Did you check all circuit breakers by opening and reclosing each one? They may be marked as to what each is for, and if so you only need to check those that are for things not working now. The other thing that I think of is the "Magnetek Power Plus panel box." I am not familiar with it so what functions does it perform? Magnetek makes converters so if that is what you mean it provides you with 12V-dc power when on shore power to keep the battery from running down. But if it is a power managment unit it may be the problem as such systems do prevent the operation of too many things on the power source that is available.
     
  9. Mark in Austin

    Mark in Austin New Member

    AC troubles

    Hello Kirk, 007, and Gary B-

    I finally had to call in the "heavy lifters", aka "The pros from Dover" aka the "RV repair service".
    All the obvious thing were perfect. (That includes the cord, power, circuit breakers, thrmostat, etc.) However, the transformer in the AC control box was bad. $200 later, is is cold in here.
    Glad it is fixed, wish I could have fixed it.
    Mark
     
  10. C Nash

    C Nash Senior Member

    AC troubles

    Thanks for letting us know what the fix was Mark. Many post problems and then do not follow up with how the problem was fixed but, maybe they never find the problem.
     
  11. Kirk

    Kirk Senior Member

    AC troubles

    Anyone know what transformer that would be? It must be a box that I'm not familiar with. None of mine have had a transformer. But I have never looked into the MagTec Power Plus either. Just wondering what it does?
     
  12. Mark in Austin

    Mark in Austin New Member

    AC troubles

    Inside the AC unit is a silver metal box. Inside it are some circuits and the transformer. The repair guy told my father (my father lives with me since his stroke) that he had to bypass it to start the AC unit. That proved it was bad. It seems to intercept the voltage signals from the thermostat and make the Ac perform. The new controller box was smaller, btw.
    Mark
     
  13. hertig

    hertig Senior Member

    AC troubles

    For those who care, a 'transformer' is an electrical device designed to convert AC at 1 voltage to AC at another voltage. They do this by having 1 coil near to another coil with a different number of windings. The primary coil generates a magnetic field as the alternating current flows through it. The magnetic field generates current in the secondary coil. If the secondary has more windings than the primary, the output voltage will be greater than the input voltage; if the secondary has fewer windings then the output voltage will be less than the input. Possibly the most common tranformer is the one in those 'wall warts' - power converters - most of us have dozens of. It takes the 120v AC and converts it to some desired voltage like 12v AC. Additional circuitry (diode bridge) then 'rectifies' the AC (flips the negative part of the AC waveform so the entire waveform is between 0v and 12v) and then filters it to the necessary degree (capacitors and sometimes more sophisicated circuitry). Voila, 12v DC from a cheap device which prevents any other useage of the outlet strip it is plugged into :)
     
  14. middle.american

    middle.american New Member

    AC troubles

    I wonder about the transformer. Low voltage might have damaged it. However, the last time my Duo-therm suddenly "did nothing" it was merely a blown fuse in the unit. I took the plastic cover off, took the galvanized cover off and changed the car style fuse. I wonder if Low voltage could blow a fuse. In any case, if your Duo-Therm suddenly doesn't do anything check this little $1 fuse and the wire harness connections before calling in the big guns.
     
  15. TexasClodhopper

    TexasClodhopper Senior Member

    AC troubles

    "Low voltage" will not damage a transformer. Low voltage will affect the compressor motor in an air conditioner, but not the transformer. The transformer in this case was probably used to supply power to the electronics/thermostat, etc. The things that people touch are usually made to work at low voltages. It helps the manufacturer obtain the UL rating.
     
  16. Krazeehorse

    Krazeehorse New Member

    AC troubles

    Excellant Hertig!! Especially the power strip part, LMAO. I would think that low voltage could cause a fuse to blow. Especially if the device were already running when the voltage drop happened. Power (usually expressed in watts) is volts times amps. So if it takes so much power (or so many watts) to run something and the voltage drops the device tries to draw more amps to maintain the power. If that amperage exceeds the fuse's rating then it does its job and opens the circuit.
     
  17. middle.american

    middle.american New Member

    AC troubles

    I wanted to error on the side of honest mechanics before suggesting that anyone might have paid the cost of a transformer for a fuse. Perhaps, the transformer went bad. However, TexasClodhopper is right that the transformer is for the thermostat control (uses low voltage) and Krazeehorse is right that low voltage to the compressor could have triggered a blown fuse rather than the transformer.

    I wanted to refrain from conspiracy theory...however Krazeehorse bolstered my suspicions. Alway check fuses and connections first.
     
  18. s.harrington

    s.harrington Senior Member

    AC troubles

    I'm confused. Unless this is a park model trailer there shouldn't be a transformer for the AC. The low woltage system in travel trailers and motorhomes is a 12 volt battery and a convertor or inverter/charger. Did they give you the bad part?
     
  19. Krazeehorse

    Krazeehorse New Member

    AC troubles

    I'm guessing the small box with a transformer and circuits is an electronic "start capacitor". It boosts the voltage for a very quick discharge to help get the motor turning when the unit is turned on. JUST a guess. And if there was a large capacitor in that assembly there is a chance that is what took a dive.
     

Share This Page