We keep blowing a 15 amp fuse?

05monacoer · 03-23-2011, 06:49 PM

We have a 15amp bedroom light circuit that blew yesterday. When I replaced, it arched and blew again. Flipped the AC distribution beaker to the circuit off, and also cut off the main breaker. Replaced, and it arched and blew again! Don't believe there's anything on this circuit but the overhead fluoresc

AFChap · 03-23-2011, 06:59 PM

You have a direct short on that circuit. The first thing to try is replacing the bulbs. If that doesn't work, take a look inside the switch. Beyond that, you will need to be able to trace the circuit wherever it goes ...you may have to get some assistance in tracking down the short.

OLYLEN · 03-23-2011, 07:14 PM

First turn off all the lights you think are on that circuit. Then replace the fuse, if it blows again disconnect the wires from what you think is the offender. Replace fuse if it still blows then a direct short and might be tough to find. If it does not blow with switch/switch's off then the light lights are the problem, then replacing light bulbs or light fixtures is in order.

LEN

Happycarz · 03-23-2011, 07:44 PM

Instead of going through a bunch of fuses, just go to the auto parts supply and buy a 15 amp circuit breaker and install it. It will protect the circuit and will reset after tripping. As you move down the circuit and find the short to ground, your circuit breaker will reset and stay on.

05monacoer · 03-23-2011, 08:34 PM

I do know there's a burned out bulb on that circuit. I'll replace it, then try replacing the fuse again. If it still blows, I may need to find help chasing down a direct short. I like the idea of replacing the fuse with a breaker. Thanks for the posts!

dons2346 · 03-23-2011, 09:59 PM

Turning off the AC power will not help as this is most likely a 12VDC problem.

Why replace the fuse with a breaker? There is still a problem and it needs to be found. Disconnect everything that you can think of that is fed by 12VDC. Install the fuse and see what happens. If it doesn't blow, then start connecting one item at a time until the fuse blows. You have now found the culprit.

MegaRoadie · 03-23-2011, 10:20 PM

The problem will be found after the fire..... jeez where is common sense here ???

Find the darned short and fix it, or make sure you dont park next to me... I dont want my sidewalls melted in the upcoming fire !

TQ60 · 03-23-2011, 10:32 PM

Some folks insert a 1/4 inch bolt, works great, the smoke indicates the short...

Enough, get a blown fuse, a 12 volt light, some wire (2o ft of zip cord) and solder

Solder one conductor to each end of the blown fuse, the bulb to the other ends.

To test, hold fuse between hot and ground and the light goes on.

Yes, same as a test light, but this does not require you to hold it and 20 feet allows the light to be placed where it can be seen anywhere you are looking for the short.

Insert into fuse position with problem, the light should lightup.

Now start disconnecting things on that circuit, when light goes out, reconnect to see light come back on.

If this does not work then a wire is pinched, hand trace wire from fuse to loads, look for flat spots or where it goes through a panel.

Always make sure you can breake it after you think you fixed it. Reconnect the wire or push it back into the corner to make sure the problem can be restored, otherwise you may be working on a new issue.

Then after you have fixed it, continue checking for more shorts as these types of problems never travel alone, they like friends.

H. Miller · 03-24-2011, 05:47 AM

Ours is an '04 Monaco product and we've done some electrical work in the bedroom area. It IS 12 volts so all the 120 VAC switching shouldn't effect it.
The Inner wall will be 1/4" plywood with a thick aluminum sheet underneath. Then 1-2" of "batt" insulation followed by the outside wall.
You'll probably find the fixture is grounded to the aluminum sheet or the "feed" wires have worn thru and are grounded.
Have you taken out the fixture?
We found all the cutout holes had VERY sharp edges in the aluminum

wa8yxm · 03-24-2011, 08:59 AM

First: The AC breaker most likely has no effect on this fuse as in most RV's fuses are used only in the DC circuit and that can be battery powered, You also said it is a lighting circuit and again, that is normally 12 volt so the only thing you can do with the AC breakers is kill the battery charger/converter.

Now, to the problem.. As others have said you have a short.. The MOST common location for shorts in 12 volt is the light socket itself, Turn OFF all the lights on that circuit and if the fuse holds (See next suggestion by the way) if the fuse holds turn them on one at a time When it blows, check that socket.

Others have suggested other places to check, Rather than repeat I'll just 2nd.

Suggestion 2:

Get a 12 volt light socket, I recommend a wedge type (This type of bulb has a flat "wedge" base with wires on the sides near each end) and a fairly large one (Back up lamp is good) Put tabs on the ends of the wires and replace the fuse with this lamp/socket assembly.

Now... A short is indicated by BRIGHT LIGHT.

If you turn on a light and the lamp comes on about 70% (Both lamps, the test lamp and the selected lamp) turn it off and move on to the next lamp. Do one lamp at a time.. The one with a shorted socket the test lamp will come on full and the lamp under test not at all.. No blown fuses that way and it's safe.

Get the matching connectors for the tabs (Insulated type please) and some more wire and test clips or probes and you have a very very very useful 12 volt diagnostic tool,,, Often much easier to use than a volt meter when chasing power problems.

Alan_Hepburn · 03-24-2011, 04:53 PM

Quote:

Originally Posted by TQ60

Some folks insert a 1/4 inch bolt, works great, the smoke indicates the short...

Actually, a .22LR cartridge is almost a perfect fit for the typical round glass fuse...

4Knights · 03-24-2011, 05:01 PM

Quote:

Originally Posted by Alan_Hepburn

Actually, a .22LR cartridge is almost a perfect fit for the typical round glass fuse...

Make sure it's already be fired! Hate to have the heat from a short cause the primer to shoot the round off.

Ron & Wendy 94 Pace Arrow 454

ga traveler · 03-24-2011, 05:31 PM

99% sure you have a bad circuit board. Fluorsent lights have a printed circuit board. these are prone to shorting out. Remove the cover remove the bulbs. pinch the center cover and remove it. you will almost for sure see a burned board. you can replace the board for about half of what a new light cost. To double check this you can take the hot wire loose from the light fixture and energize the circuit. if the fuse doesnt blow the light is the problem.