Rear monitor

Discussion in 'General RVing' started by salvador, Feb 10, 2007.

  1. salvador

    salvador New Member

    I have a foretravel unihome with rear monitor. The monitor also is linked with tv type screen that shows, compass, tank levels, lp levels, etc. It has a 5 amp fuse and keeps blowing it. How can I start out to find out here the short is located. This is a big deal since so many systems are monitored thru it....thanks...doc.
     
  2. hertig

    hertig Senior Member

    Re: Rear monitor

    How often does it blow the fuse? Under what conditions? More information might point to a culprit or at least cut down the possibilities.

    Usually the fuse is in the power supply line, which means the stuff fed by that power line is drawing more than designed or that unexpected devices were added to the circuit. If the wire goes directly from the fuse to one device, then there would seem to be something wrong with that device or the wire going to it. If it goes to more than one device, then it gets more exciting. If the fuse blows 'immediately' then a current meter in line with each device might indicate the culprit. If the fuse blows intermittantly, then I might be tempted to measure the 'normal' current, then wire in a separate fuse for each device of that amount plus a little bit, and see which one of the new fuses blows to isolate the bad component or wiring.
     
  3. TexasClodhopper

    TexasClodhopper Senior Member

    Re: Rear monitor

    " It has a 5 amp fuse and keeps blowing it. " That's what Sallyberetta keeps telling ME! :eek: ;)

    You are kinda implying that the fuse that is blowing is right on the monitor (the built in fuse.) If that is the case, then you are done troubleshooting. The problem is inside the monitor. Might be time for a new one.

    While troubleshooting CURRENT related problems like this, always keep in your mind that something is PULLING too much current from the battery.

    The battery is UP HERE; the wiring is a little PIPE for current; the FUSE is in the wire/pipe; the monitor is DOWN THERE; and is PULLING too much current THROUGH the FUSE. (There could be more than one fuse.) There could be more than one appliance connected to that same wire/pipe between the FUSE and the monitor. (Unless the fuse is right at the monitor.)

    Like John is saying, you need to determine if the monitor is the ONLY appliance between the FUSE and the chassis.

    Or, you could have a "short" (bare wire connected to metal). That problem would blow the fuse as soon as you put in a new one (with the monitor disconnected).
     
  4. Kirk

    Kirk Senior Member

    Re: Rear monitor

    When I used to trouble shoot for a living, there were several things that I always considered first. #1 question is how quickly does it blow? If it is an instant flash when plugged in and gone immediately, then there is a chance of a bare wire or some other direct short. On the other hand, if the system works for a time but blows after a few minutes, that would usually indicate a problem in one of the devices that are fed by the fuse. If the fuse holds for several hours of use but fails only occasionally, then it may be related to just what is happening at the time it fails. That could indicate what is causing it by paying very close attention to any operation that takes place when the fuse fails, to see if it is always at that same operation.

    Another tool to diagnose the problem would be to look for some way to seperate the loads to see if removing the back up camera will keep it from blowing, then remove the monitor to see if it will work and not blow the fuse? Does the fuse blow when the back-up monitor system is not in use? If it does it is a good bet that the problem is not in that part of the system. But to make sure, disconnect it. It is possible that some problem in the wire harness of the camera or monitor could cause the fuse to blow, even when not in use so make sure. Do not assume anything unless you test the theory. Most systems supply power from the monitor back to the camera so it too could be the culprit.

    Unless you have a very accruate meter, measuring the current probably will not tell you very much. Before you do that, you will need to look in the manuals or on the particular item to see what it should draw as max. current. In a circuit that uses a 5A fuse, those loads are probably going to be in the range of 1A to 1.5A and a low price meter isn't accurate enough to tell most of us very much. If you have a meter like my Fluke 77, it is very accurate so the information may be helpful. You must put the amp-meter in series with the item you are checking to get an accurate reading.

    Another thing that could cause this problem, but is not likely is that too high a voltage might. Since a fuse is a current device, high voltage will drive a greater amount of current and if high enough and above the designed operation voltage range the fuse might blow.

    Make a few tests and come back with more infromation and we might be able to help more.
     
  5. salvador

    salvador New Member

    RE: Rear monitor

    Thanks guys. Had the front dash panel up and tracing the wires to monitor. Found the wiring schematic for the camera/monitor. Will probably have to take this one in. The monitor has, rear camera, all tank levels-water, black,grey, plus lp, barametric pressure, temp and compass. The schematic looks like that of a two bedroom house. When new 5amp fuse is put in it blows it as soon as the monitor switch is turned on, I can actually hear it pop the fuse. Can't find any breaks in wiring as far as I can follow it, and I have traced the wiring from the fuse to the monitor and switch, must be in one of the other wires to one of the other monior functions,tanks, etc. Thats alot of area on this 34 foot RV
    Thanks...Doc :)
     
  6. hertig

    hertig Senior Member

    Re: Rear monitor

    The inputs to the monitor are not a major source of concern. It is what devices that the fuse supplies power to which needs to be investigated, not signal lines. If a device is bad and it draws more current than it should OR too many good devices are being powered by the fuse, then the fuse will blow. Invalid values on the signal lines will cause unpredictable behavior, but it would be very strange indeed (and poor design) if an input to the monitor could cause a power fuse to blow.

    So look at all devices which are powered through that fuse, either directly or through the monitor.
     
  7. TexasClodhopper

    TexasClodhopper Senior Member

    Re: Rear monitor



    You STILL aren't making it clear WHERE the fuse is LOCATED.

    Is the fuse in a panel somewhere REMOTE from the monitor?

    If the fuse is right at the monitor, then you can stop troubleshooting. The monitor is the problem; not the wiring.
     
  8. salvador

    salvador New Member

    Re: Rear monitor

    txCloddheopper- the fuse is in the fuse cluster about a foot away from the monitor, not right on the monitor. :)
     
  9. TexasClodhopper

    TexasClodhopper Senior Member

    Re: Rear monitor



    OK. The problem is between there and your monitor; if not your monitor.

    But then you said it blows when you turn on your monitor. If it doesn't blow when you put in a new fuse, then the problem is IN your monitor.

    I would bet there is a filter capacitor or a "reverse polarity protection" diode inside that has shorted.

    More likely the capacitor.
     

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