Converter Humming, probable short

usmcbecker wrote:
Thanks for all your responses. First of all, my converter is progressive dynamics PD4045KA. It still makes noise when the battery is disconnected. The battery did drain even when all the breakers were flipped off, so I was thinking that it may be one of the DC systems, but I am not too sure. As for the fan, its not what's making the noise, and it does move and twitch, but I have yet to see it turn on.

As for the humming, it is something that has started recently. I bought it off the lot a couple of years ago and I would have definitely noticed it before.

Would the fan issue drain the battery even if all the breakers are off?

I think you have two problems, well maybe just one big problem. It sounds like your charger has failed or you have a blown fuse and are not charging the battery. The second issue is that the fan should spin or stop. If it's twitching and not spinning I think it has a problem and might be causing something to overheat and hum. Here's a few tests you can do, hopefully you have a meter of some kind to do some checking.

For the dead battery:

• Unplug the shore power cord from the trailer so you are on battery only.
• If you have a meter set it on the DC scale and go take a reading of the battery by measuring across the terminals and remember or write down the voltage.
• If you look at the picture that RoyB posted you will see two green fuses separate from the other fuses. Those two fuses are your reverse polarity fuses to protect the electronics in case you inadvertently hook up the battery backwards.
• The thick red and black wires right next to those two fuses are the feed to the battery.
• Your board will look different but you will still see the large wires on the board that lead to the battery.
• With your meter put the positive (+) lead on the screw where the red wire connects to the board. Do the same with your negative (-) lead on the black wire and take a reading.
• Your reading should be withing approximately .1 volt from the previous battery reading.
• If you have voltage at the battery and no voltage at the board then you have a disconnect (blown fuse, tripped circuit breaker etc) between the battery and the board and your battery is not getting charged.
• However if you get the same reading between battery and board then your charge circuit is at least complete.
• Now look at your reverse polarity fuses. Notice that right next to the numbers on the fuses are two slots or holes in the plastic.
• With your meter put the negative lead on the negative (black) wire on the board and touch the positive lead to a little slot on the reverse polarity fuse.
• You should get battery voltage on all four slots (two per fuse).
• If any fuse has voltage on one slot and no voltage on the other slot, that fuse is open and needs to be replaced.
• Now plug in the shore power and using your meter measure the voltage on the wires on the board. You should see 13+ volts when on shore power.
• If you get 13+ at the board go check that the voltage at the battery is the same as you measured at the red and black wires on the board.
• If there is a difference of more than approximately .1 volt you have a resistance problem somewhere (probably out on the tongue)where there is a poor wire connection.
• if the voltages at both the battery and charger are 13+ volts, you probably have a bad battery.

Have no meter, unplug the trailer shore power and grab a friend. Wait until it's dark outside. Stand in the trailer, turn on a light and stare at it. Have your friend plug in the shore power. The light should get brighter. :)

As far as the humming noise:
My guess is that you have a transformer humming or the fan is stuck. Does the hum reliably happen every time you plug into shore power? Can the fan wires be unplugged off the board? If so try unplugging the fan and see if the noise goes away.

If you have a short (1 foot or so) piece of hose (garden hose, fuel line, radiator hose etc) you can make an inexpensive mechanics stethoscope. When the hum is occurring put one end of the hose in your ear. Place the other end of the hose near the fan and other components in the charger. The hose will allow you to isolate the component that is making the hum.