Radio fuse continues to blow

I returned a couple of days ago from a 24-day trip with a problem that perplexes me. The new radio that I had installed stopped working after a few of days out. I figured that the constant bouncing and/or the heat from the fridge had disabled it. When we got home and I pulled the radio and checked its fuse and connections and could see no obvious problem. Further investigation revealed a blown 15-amp fuse on the converter panel. I replaced it and the radio worked – for all of about 15 seconds and that fuse blew also. Long story short…that fuse position blows a fuse after a few seconds…and it makes no difference whether the radio is connected to its power source. I’ve visually traced and checked all the wiring that I can access and cannot find any type of hard short. All the other electronics work fine.

There are two perhaps unusual conditions that might contribute to this problem: 1) on the third day when I opened the rear storage compartment where the battery is on our model I found the new battery on its end and virtually all the acid drained out. I up righted it, cleaned up the mess, and added water. It takes a charge and seems to work all right; 2) when inserted a new fuse in problem position there is pronounced sparking as the fuse prongs contact the panel slots. Perhaps this is normal, but I’m suspicious that it isn’t.

I’ve removed all the covers on the converted box, checked all the connections and can see nothing amiss.

Here’s hoping that some of you can give me some clues and/or direction on what my problem might be, and thanks much in advance.

Bill

1) on the third day when I opened the rear storage compartment where the battery is on our model I found the new battery on its end and virtually all the acid drained out. I up righted it, cleaned up the mess, and added water. It takes a charge and seems to work all right;

If all the acid drained out of the battery it would need new acid - not just water. You need to have the specific gravity of the acid checked because it's probably not very good and the battery will fail very soon. Also, where the acid drained needs to be neutralized with baking soda and water until there is no fizzing of the baking soda. Otherwise, the acid is still active and will contaminate anything you put in there. This would not cause the other problem with the fuse - that is probably something else.

[Bill]

Wow! Interesting problem.

First, it appears that the radio is the only thing on that fuse, so the problem is either in the wiring from the fuse to the radio, or in the radio itself. No other suspects. The fact that the new fuse sparks a lot when you put it in suggests that there is, in fact, a short somewhere downstream of the fuse.

Why don't you pull the fuse, turn the radio off, pull it out from above the refrig, and disconnect the radio's power wires from the wire above the refrig. Now put in a good fuse - does it spark? Wait a while. Does it blow? If the answer to either is Yes, then the wiring is at fault.

If the problem appears to be in the radio, can you connect it to a different source or a different circuit? If the fuse on the other source blows, then the problem is in the radio. I'm assuming you don't have an ammeter to measure the radio's current.

Re the spilled battery acid, a couple comments.

First, was the spilled acid totally confined to the plastic battery box, or did some escape and get into the battery well? If any escaped, I hope you used a large amount of baking soda, sprinkled throughout the well, to neutralize it. In that case, I would also leave a 1/4" layer of soda in the bottom of the well - forever.

Second, if acid escaped and you replaced it with water, then the acid solution is now too weak. You might consider buying a hydrometer to measure the acid strength. Or it might be simpler just to drain all of the acid out of the battery, and refill it with new acid. You can buy a bottle (actually a bag) of new acid cheaply from an auto supply store.

Third, I doubt that the upended battery has anything to do with the radio fuse problem. On the other hand, if the radio problem started at the same time, I'm hard pressed to explain the coincidence.

Let us know what you find.

Bill

[mjlaupp]

Bill,
To address the "unusual conditions":
1) While you can add water to a battery to replace that lost from evaporation. In this case the acid remains in the battery. You should (must) replace spilled acid with acid. Your battery now has a much reduced AmpHour rating. Take it to a battery shop for refurbishing or replacement. Also find a way to secure the battery to prevent it from turning over.
2) There may be some sparking on the radio fuze when you replace it since the radio draws a small current for the clock and to keep the station presets in memory. There should not be "pronounced sparking" unless the radio is turned on when you insert the fuse. It sounds like you have a short in the wiring and I suspect it is behind the converter panel under the tub. That battery acid probably ran under the wall and under the tub area. It is probably still working on the components it found there. You will have to remove the converter panel and check. Be sure that the TM is not plugged into shore power when you do this.
3) When you cleaned up the spilled acid, did you use baking soda to neutralize any remaining acid? If not, it is still working on your TM. I hate to think what might be happening to the aluminum skin on the floor.
Mike

Thanks Jim, Bill, and Mike.

The fuse does blow, even with the radio totally unplugged from the power source.

Most of the acid spill was confined to the battery box and drained out the vent hole in the bottom of the TM skin. Stripped all the paint off the jack on that side. I have used baking soda in the floor area and will leave some there as suggested. Also, will definitely rig something so that it will be impossible for the battery to ever turn over again. I also have it on my improvement list to put a support, secured to the frame member, under the floor where the battery sits. I figure over time that single sheet of aluminum will give way.

I'll return to searching for a short. This is a challenge because so much of the wiring is in accessible.

Will let you all know how this problem is resolved.

Bill

Originally Posted by bfezel

The fuse does blow, even with the radio totally unplugged from the power source.

You have already eliminated the radio as the source of the short. Just to confirm, the radio's in-line fuse is probably no more than 2 amps, and radio probably doesn't draw more than .5 to .75 amps. You can check that with an ammeter.

Since you are still blowing the 15 amp fuse without the radio connected to the circuit, the short is somewhere in the line between the fuse panel and where it connects to the radio in the refrigerator area. It will be a tedious project, but I suggest you start at the converter/fuse panel, pulling the converter out of it mounting area so you can see behind it. Begin a physical inspection of every inch of the wire that connects to the "cold side" of that fuse, with the fuse out of the holder. Look for places where the wire may be pinched by or under something metal, or is rubbing against a sharp metal surface. Remember, the wire is the "hot" or positive side of the circuit (battery) and anything metal is connected to the body of the trailer, which is connected to the negative side of the battery.

I recently had a similiar problem on the 110VAC circuit to the microwave oven in our trailer. However, when I disconnected the microwave, the short stopped so I knew the problem was in the oven. Taking the back cover off the oven, we found that the insulation of one of the wires had been rubbed through due to vibration and a poorly "dressed" wire inside the cabinet. Some electrical tape and "dressing" the wires to make sure they don't rub against sharp edges solved this problem.

Good luck in your search.