Forum Discussion

wbwood's avatar
wbwood
Explorer
Sep 03, 2015

Electrical Assistance

We have a 2013 Class C motorhome that came with a 32" Jensen LED 12 volt tv. It is mounted in a frame with storage behind it. In the last year, we blew the inline fuse in it. I noticed that the wiring got damaged from opening and closing the storage area. Basically it pinched the wire. I spliced the wires back and put in a new fuse. TV worked. After watching it for a while (few hours) on the next camping trip, the inline fuse blew again. I noticed it was hot to the touch. The tv is 7.5amps. The inline fuse holder has a sticker on it that says 8amps. I replaced it with a 7.5amp fuse and it blew again, and once again hot. So I ordered some 8amp fuses. Replaced the fuse with an 8amp one and immediately starts getting hot again. I removed the fuse and did not attempt to use it again.

Any idea of why this is happening? What can I do to correct it, short of purchasing the AC power supply for it or replacing it with an AC tv?
  • Salvo's avatar
    Salvo
    Explorer
    Sep 03, 2015
    Good answer. There could be considerable voltage drop from battery to tv. The tv has a watts rating, not amps. The lower the voltage at the tv inputs, the greater the current. You may be exceeding 7.5A.

    You can measure the voltage drop between battery & tv. Put one voltmeter probe on the + battery terminal and connect the other probe to the + tv input. The meter should be on the 2V scale. The meter leads will need to be lengthened for this measurement. Measure the ground cable the same way.

    You can also measure the tv current. Voltmeters usually have 10A capability. Remove fuse and insert amp meter.

    Now we got all the pieces of the puzzle to fix it right!

    westend wrote:
    Amperage increases with lowered voltage. If you have small wires connecting the TV to the DC source, you will have voltage drop and increase the amperage and the heat. The same is true for a partially discharged battery when powering DC devices.
  • enblethen's avatar
    enblethen
    Nomad
    Sep 03, 2015
    The TV is marked to draw 7.5 amps. You should be feeding the unit with a fuse greater then that. I would get a new fuse holder, I prefer blade style, and install a ten amp fuse.
    Yes, it is normal when operating at close to the max rating for the fuse to get warm, normally it is resistance within the fuse and holder.
  • wbwood's avatar
    wbwood
    Explorer
    Sep 03, 2015
    westend wrote:
    Amperage increases with lowered voltage. If you have small wires connecting the TV to the DC source, you will have voltage drop and increase the amperage and the heat. The same is true for a partially discharged battery when powering DC devices.


    so are you saying this is normal? It wasn't like this before the wires got pinched and shorted the fuse.

    Batteries are fully charged.
  • wbwood's avatar
    wbwood
    Explorer
    Sep 03, 2015
    beemerphile1 wrote:
    Replace the fuse holder or pinch the contacts together so it holds the fuse tight.


    Its the glass type fuse with the screw cap on it...
  • westend's avatar
    westend
    Explorer
    Sep 03, 2015
    Amperage increases with lowered voltage. If you have small wires connecting the TV to the DC source, you will have voltage drop and increase the amperage and the heat. The same is true for a partially discharged battery when powering DC devices.
  • beemerphile1's avatar
    beemerphile1
    Explorer
    Sep 03, 2015
    Replace the fuse holder or pinch the contacts together so it holds the fuse tight.

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