Help with furnace and wiring, please!

[Kevin A]

OK, as is normal, we are on a trip with our 1988 Silver Cloud and something needs fixing.
1. Our Atwood Hydroflame 3531-I (1988 original) was working fine and it suddenly quit heating this morning around 3 a.m. The blower runs, the igniter goes, and I smell propane out the exhaust. Just no burner after working fine for about 4 days straight. It has power and propane. Any ideas?

2. We came home yesterday and smelled something like hot wiring. I quickly traced it to the 15 A fuse holder on the converter. The screw off fuse cover was too hot to touch. That fuse protects a simple light circuit...about 13 12v bulbs if they're all turned on, which they never are. I traced the heating condition to the switch operating 6 entry hallway bulbs and the switch operating the 3 bathroom vanity bulbs. No other switches on the circuit cause the fuse holder to heat up. I put in a new fuse, but no difference. What would cause this problem?

Thanks!

[John in Michigan]

Kevin, concerning the hot fuse, if all 9 bulbs that you mentioned are on and if they are all incandescent, and if they are, for example, Type 1141 bulbs, they draw about 1.5 amps each. That would be pushing the limit on that circuit and could cause a hot fuse.

EDIT: Type 1156 bulbs even higher at 2 amps each. SECOND EDIT: Type 1156 bulbs are actually 2.24 amp each...

[thrifty bill]

John beat me to it.

On #2: Trailer and wiring is 30 years old. Typical RV fixtures are really cheaply made. Easy to have a short somewhere, bare wire touching, whatever. Good excuse to convert to 12 V LED fixtures. I am not talking about plug in replacement bulbs, I'm suggesting replacing the entire fixture. Much more light at dramatically lower current draw. 15A for a Silver Cloud is not much.

Standard old style RV bulbs draw 1.5 amps per bulb for the 1141 bulbs (18 watts = 12 V x 1.5 amps). If you have multiple bulb fixtures, then multiply. For example, on my 1977 Trillium the original fixture above the sink was three bulbs, so that is almost 5 amps just for the one light. You will have other items that draw 12 V power, water pump and furnace electrical. FWIW, the capacity on my 13 foot Trillium was only 72 watts. So you are talking 4 incandescent bulbs and I would be out of capacity. Since the Trillium had 9 light bulbs, I was way over the limit if I happened to have them all on or even the majority of them.

Sounds like you have nine bulbs just between the hallway and bathroom. Count them all and I bet you are way over the capacity of the system.

Then in my case, the fuse holder itself is old and brittle. Its on the project list. You have to wonder what the useful life on this RV electrical stuff is, I know several of the incandescent lights in my Trillium had lose wires and bad connections. I was asking for trouble. Many of us are far beyond the original design life of these trailers (just my opinion). Its a testament to the original builders that you still see so many of them still in use!


In the case of my Trillium, I went from 9 bulbs that if all on would draw 162 watts, versus a capacity of 72 watts. With the conversion to LED, I now have 12 lights (more light), but only drawing a maximum of 36 watts, which is well under my system's capacity. OK, with my old incandescents, chances of having ALL my lights on at once is low. But the chances of being over 72 watts would be high.

And +10, if your lights use 1156 bulbs, the math is much worse as they draw over 2 AMPs per bulb.

And double check your count. If you are at nine bulbs between the bathroom and hallway, then I am guessing you are going to be over that 13 number total for the entire trailer. Count every bulb, not just every light fixture. Its not unusual to get one fixture with two or more bulbs.

[Kevin A]

Thanks, John. Unfortunately, just having 3 bulbs lighted causes the hot fuse and that's well under the 15 A. I'm going to pull the panel covers and look for pinched or loose wires next

By the way, the propane tanks were very low, causing a lack of pressure to the furnace. They are now refilled and the furnace is working again! Stupid me!

[John in Michigan]

To add to Thrifty Bill's comment, in my Trillium 4500, I cheaped out and just replaced all the Type 1141 bulbs with Type 1141 LED bulbs. They use about one-tenth the power of the Type 1141 incandescent bulbs.

Also, if you decide to switch to LED, go with higher quality, e.g., lights sold by superbrightleds dot com. Look for LED lights rated for 10 to 30 volts, capable of withstanding fluctuations in power.

[John in Michigan]

OK great Kevin. Let us know what you find in the wiring.

[Kevin A]

The hallway 6bulb fixture does use 1156 bulbs, so 6 x 2 A for 12 amps. I'll look for LED bulbs or fixtures, too. Thanks!

[John in Michigan]

Kevin, apparently spec for the Type 1156 bulb is 2.24 amp / 27 watts.

[jimknoch]

Originally Posted by Kevin A

The hallway 6bulb fixture does use 1156 bulbs, so 6 x 2 A for 12 amps. I'll look for LED bulbs or fixtures, too. Thanks!

Kevin,
I just replaced the 1156 bulbs in my over dinette fixture with some I bought at Walmart.com for $11.98 per 10 bulbs. Watch for the color rendition, you'll probably want "Daylight" or "Soft White"(frequency around 3500) Unless you really like the bluish tint of the "Cool White"(freq. 5000 or higher). Since the change, I now have all lights in the TT converted to LED and I never hear the cooling fan on the inverter come on any more.

Please look at the color of the metal on the fuse holder. If it is anything like starting to turn copper colored, it has likely annealed and will be loose and a loose connection will continue to create heat as the electrical connection becomes high resistance. It will eventually cascade to a failure.

Good Luck & Good Camping ... Jim (Swampy)

[Kenny Strong]

why would the fuse panel be so hot, and not blow the fuse? How does it get hot? the amp draw are exceeded? I know nothing !

[gordon2]

Originally Posted by Kenny Strong

why would the fuse panel be so hot, and not blow the fuse? How does it get hot? the amp draw are exceeded? ..!

Yes, probably the amp draw is exceeded, but not the fuse rating. Instead a bad connection that can no longer pass the current, or perhaps a bad fuse that is way out of spec. Bad electrical connections are a common cause of heat and fire.

[Byron Kinnaman]

Originally Posted by Kenny Strong

why would the fuse panel be so hot, and not blow the fuse? How does it get hot? the amp draw are exceeded? I know nothing !

Fuses are rated at current and time. At one time I tested a 1 amp fuse with 2 amps through it. It got hot but didn't blow after one hour when I gave up.

[jimknoch]

Originally Posted by Kenny Strong

why would the fuse panel be so hot, and not blow the fuse? How does it get hot? the amp draw are exceeded? I know nothing !

Kenny, All it takes to get hot is a loose connection or something drawing more current than it is supposed to draw. Even if the current is below the fuse rating, a poor connection creates a high resistance and the power consumed (heat generated) is proportional to the square of the current times the resistance. A poor connection or high resistance connection will continue to overheat until it cascades and the connection fails usually because once the metal contacts are overheated, they become annealed (softened) and lose their springiness that keeps the connection solid. In actuality, once enough heat is generated the fuse will melt and drop the circuit ... assuming you haven't set the wire insulation on fire already. If it is an overload situation, you should expect the fuse to blow unless someone put a bigger fuse than was called for to protect the circuit.

The original cause of the heated connection if not caused by an overload (too much electric current over time), can be anything from the contacts becoming wet or even a bug getting squashed on them or even a mouse going to the bathroom on them and starting corrosion between the metal contacts. If you allow the fuse panel to fail, you will have an expensive repair job (replacement) at hand. I suggest you consider examining the contacts in your fuse panel and burnish the contact surfaces of the fuse and holder with a very fine emery paper, then apply a dab of contact inhibitor on them. You should also look at reducing the amperage load on the circuit if at all possible.

That is probably enough physics for today, good luck making the repairs... Swampy