Diagnosing electrical problem . . . your thoughts?

Discussion in 'Power - Site Power/Batteries/Generators/Solar' started by Machta, Jul 14, 2010.

  1. Machta

    Machta New Member

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    Good morning, all!

    In March we bought a 1998 Chalet "Classic," which we love. But I'm beginning to suspect that it was sold to us with a fairly major problem in the 12v system. Tell me what you make of this series of events:

    1. The battery was dead when we bought it.
    2. Thinking the battery was bad, we bought a new series 27 and installed it in March of this year.
    3. While installing the battery, my husband found that one of the fuses had actually gotten so hot the plastic had melted. In addition, one of the wires from the battery had gotten hot enough at some point that the outermost insulation layer is brittle & flaking off.
    4. When unplugged from the house current, the battery goes dead within 48 hours. It charges fine.
    5. We have replaced the LP gas detector, thinking it was malfunctioning when it would not stop beeping (in hindsight, maybe it was just very sad with no power?). The wires looked good.
    6. We have replaced the porch light fixture since it worked intermittently. The wires to it looked good, and it now works flawlessly.
    7. The AC system (house current) works flawlessly.
    8. The only fixtures on the 12v system, as far as I can tell, are: a 12v "cigarette lighter" type outlet (untested since we never use it); 2 ceiling lights (work perfectly), porch light (replaced, works perfectly), water pump (untested, since we don't use the trailer's water system, but the switch looks like it's supposed to light up when in the "on" position, and it does not), and, of course, the running/brake/tail lights (which all work flawlessly).


    This sounds like a short in the 12v system, right? Unless somebody has another idea, I think I'm going to concentrate my next efforts on the water pump. We don't use it, so I may take it out and replace the faucet with a low-profile hand pump (does anybody have one they want to get rid of? I have only 3 1/8" clearance). I suppose I should also test the 12v "cigarette lighter" outlet as well.

    Whaddya think? Am I on the right track?

    Thanks in advance!
    Machta
     
  2. Mpsabatt

    Mpsabatt New Member

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    A short circuit will blow a fuse or trip a circuit breaker. An overload will cause wires to become over heated which inturn causes insulation to degrade. It could be that the PO plugged something into the CL socket that drew a very high current. If the fuse holder was not making good contact it would become overheated. Heat measured in watts is equal to the current(amps) squared times the resistance in ohms. You are not looking for a short circuit but rather an overload and probably a loose connection or corroded fuse at the melted fuse holder The fact that it takes 48Hrs for the battery to go dead indicates there is a low current load on it IE a CO monitor.
     
  3. Raycfe

    Raycfe Waterford Ct.

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    Bad connections will make thing worse. What I would do is unplug the PU, shut every thing off. Then remove the Positive battery cable from the charged battery. I would then put a test light between the cable and the battery post. If the positive terminal has more than i wire do them one a a time. If the light glows, something is "on" causing the battery to go dead. Then I start to pull fuses, then disconnecting things until the test lamp goes out. If the water pump, refrig, furnace are still turned on but not working, disconnect them. I would also inspect the positive lead going into the PU, for rubbing on the metal frame etc. The positive lead should be replaced with a new fuse holder or circuit breaker. Everything should be protected by a fuse in some way. Please post what you find, I should be simple once you find the problem.
     
  4. Woodzeke

    Woodzeke New Member

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    Machta, good advice given so far. A loose or bad connection will heat up and arc under load. All of the inline fuse holders should be changed out to eliminate a strained weak link. Any melted wire should be replaced with a good splice. The CO detector will always be on when the battery is connected, and when the battery voltage gets low, at least on mine, the detector will emit a high frequency squeal. I always pull out the blade fuse located on the converter that feeds co detector when I store the pup. A volt ohm meter which has an 10 amp draw setting would be nice to trouble shoot your 12 volt system. The charger circuit that is built into your converter may be bad and drawing the battery down. A check of the voltage across the battery with the pup plugged into the AC should be over 13 volts dc if it is charging a low battery. A very low amp draw may not may not light up, or barely light up the test light put in line between power cable and charged battery. The digital amp meter will detect the low amp draw. CL plugs are rated generally at 15 amps, but will draw more if they are dirty. The water pump has a pressure switch that may be turning the pump on and while being stored, so the master switch to the pump should be off when water is not needed. As was posted earlier a dead short to ground would have blown a fuse immediately when the battery was hooked up provided the correct fuse was installed. Sounds like the biggest amp draw you have should be the water pump provided you do not have a gas heater or 12 volt fridge. BTW the running lights and brake lights should not draw off the trailer battery, but if you have electric brakes and and a break away switch that is in the own position, this may be your problem.
     
  5. Machta

    Machta New Member

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    Thank you all for your thoughts! I'm a real novice when it comes to electricity, so this is all REALLY helpful!

    I have new diagnostic information, which comes with a bit of philosophy. I spent a couple of hours last night with my 83-year-old dad, an engineer who is one of the smartest people I know. He and my husband both have handy-dandy voltmeters that show (I think) that when we tested the wires as they connect to the battery, there was no persistent short in that end of the system.

    So, somewhat confounded by that result, we decided that the problem was one of the following:
    -- an intermittent short (very difficult to isolate?)
    -- a bad battery (even though new, sometimes it happens)
    -- a bad power inverter (yikes)

    In order to test all of that, we decided to plug the trailer in with the battery hooked up to see if the battery would charge (I had forgotten that last weekend my husband charged it with the trickle charger). Then, assuming the battery charged, we planned on unhooking it from the circut and letting it sit a few days to see if the power would drain, "by itself," thus indicating a bad battery.

    However, we may have found the culprit, since the battery did not charge overnight. My husband tested the inverter this morning, and sais that the AC side of the inverter is fine, but the DC side is "dead."

    At this point, we are inclined to replace the power inverter and see if that fixes the problem, but because they are expensive, I wanted to check all you good people on popupportal first to see if you think this is a logical next step. Plus, if we do need to replace the inverter, this would be the perfect time to invest in one that can also handle a solar charger as well, right? So, again, I ask your thoughts on the whole mess . . .

    And here's the bit of philosophy I promised: even though Dad and I didn't find the problem last night, we had a really nice time talking about all of it. He loves troubleshooting problems like this, but because he's slowing down a lot he doesn't get the chance to do so as much as he would like. His mind is still very sharp, and it was fun to learn from him again. Thus proving that even when parked on the driveway and having a big problem needing work, pop up campers can bring a family together.



    Thanks for all your help!
    Machta
     
  6. Raycfe

    Raycfe Waterford Ct.

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    The converter (not inverter) may have a protection fuse inside it. And to check if the converter is working, just disconnect the battery ..... do the interior lights and other 12 volt items still work with the PU plugged in? If they do converter is working. Some older converters do not have a charger built in or may have a selector switch. Hope this helps
     
  7. Machta

    Machta New Member

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    Ah, good point! We tried the test you suggested, unhooking the battery & plugging the trailer in. The DC system did not work--none of the lights worked, etc. So, in your opinion does that pretty much mean that the power converter is bad? And if so, is there a good yet inexpensive one we can get that would also allow us to (someday when we have enough pennies) put a solar panel on the trailer to charge the battery when "dry" camping?

    Thanks,
    Machta
     
  8. Raycfe

    Raycfe Waterford Ct.

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    Did you look for fuses. Post any model numbers etc that are on the converter.
     
  9. Machta

    Machta New Member

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    Fuses look good. Converter is a MagneTek 6720, Series 6700. We found the original owners' manual. It was originally purchased in August of 1998.
     

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