Mystery of blowing fuse resolved

[ricemanwm]

The 15 amp fuse that protects the interior lights and exterior porch light along with the light under the steps of my 2017 265RLSW would blow intermittently. Completely driving me crazy because it was not a constant fault. Difficult to impossible to troubleshoot a potential short when the fuse was not blowing. Isolated it on a camping trip to the porch and step light; flip on the outside lights, fuse blows taking out living area lights as well. Kept the outside lights off for the trip and when I got the trailer home, no more blowing of the fuse and the outside lights worked perfectly.

Made a trip to Disney, no blowing of the fuse, bring the trailer home and finally the fuse blows at the house where I can isolate it. I’m careful not to disturb any wires while figuring this out; certainly don’t want the fault to go away. With the light switch off, I disconnect the connectors at the step light and read resistance between the wires supplying the power and return and perfect, I have a dead short. I follow the green 12VDC wire back and it was running under the bracket on the side of the fresh water tank. I remove the bracket and the wire is squeezed flat and right where it came out from under the bracket I saw exposed copper. Finally I had found the interment short.

Looking closely at the exposed copper, several strands were broken so I cut out the damaged area and put an inline splice, soldered it up, slid some heat shrink tube over it and problem solved. All the lights work, no more blowing fuses and the short is resolved. The bracket is not a support for the water tank but rather a positioning bracket to keep the tank from sliding around. Obviously I reinstalled the bracket without the wire running under it and to the side where all the other wires are running.

Just figured I would pass this discovery on in case someone else was battling with something similar. Wouldn’t be a bad idea to roll around under your trailer and look to make sure you don’t have any wires pinched between a bracket and the frame. Other discovery’s were wires running through bare holes in the frame, I use a small piece of heater hose, split it down the side and zip tie it so the wire insulation is not rubbing on the metal hole. It would probably take years of travel vibration to wear through the wire insulation but nothing wrong with some homemade grommets. The picture of the bracket is after the repair.

[stateboy]

Nice detective work! Thanks for sharing your findings.

[John7349]

X2 on detective work! Sometimes ya just have to start at the beginning and trace it till the problem is resolved.
Bet you felt great when you found it!

[RedHorse1]

Originally Posted by 36fire412

Nice detective work! Thanks for sharing your findings.

3X! Thanks for the post.

[wabirch]

Good find and repair.

[Victoria]

That is fantastic that you found it. Can I get some input on our camper electrical noise? we have not camped in our new to us octane T26Y yet but we have been working on it to improve a few things. There is a crazy high pitch fan type noise coming from the fuse box. All we have been able to deatermine is that it NOT the fan. It is a really annoying high pitch!

[bigironcoder]

Good job! Based on my experience, it's best to send the kids and wife away when trying to trace out a short under the trailer. When I was under my new trailer checking for holes that needed sealing, I took the time to install split tubing around any wires that ran through or over the steel framing.

[travelingjw]

This is a great post, thanks. My electronics teacher from over 50 years ago always taught us to start right at the beginning. A lesson that has helped me many times over the years.

[ricemanwm]

Originally Posted by Victoria

That is fantastic that you found it. Can I get some input on our camper electrical noise? we have not camped in our new to us octane T26Y yet but we have been working on it to improve a few things. There is a crazy high pitch fan type noise coming from the fuse box. All we have been able to deatermine is that it NOT the fan. It is a really annoying high pitch!

My first guess would have been fan bearings but you say you’ve ruled that out. In the Navy on our ships the large transformers produced a high pitch noise but to be honest I have never heard a small 60hz 120VAC transformer make much if any noise. There is a transformer in your power converter that steps down the 120VAC and then sends it through a bridge rectifier to provide the DC voltages the camper uses. If you’re certain it is coming from the converter/power distribution unit it is pretty much a remove and replace module.

I would go camping. Utilizing all systems on a camping trip, the problem may work itself out. No telling how long the camper has been sitting up if you just bought it and I’m assuming by you saying new to us it was used and no warranty is applied.

Before I bought a new power converter I would rule out all other possible sources of electrical noise. Might try turning off each of the 120VAC breakers that supply the systems one at a time to see if the noise changes. You can do the same isolation with the fuses too just make sure you secure power to the trailer and disconnect the negative battery cable before pulling or installing fuses. If the noise is still present with breakers off except main feed breaker and fuses removed I would look at replacing the converter module. This is just a rough guess since I haven’t actually heard the noise you’re describing. Good luck to you.

[TakerEasy]

Murphy always taught me that it doesn't matter where you start, you will find the problem at the last place you look

Originally Posted by travelingjw

This is a great post, thanks. My electronics teacher from over 50 years ago always taught us to start right at the beginning. A lesson that has helped me many times over the years.

[Victoria]

Originally Posted by ricemanwm

My first guess would have been fan bearings but you say you’ve ruled that out. In the Navy on our ships the large transformers produced a high pitch noise but to be honest I have never heard a small 60hz 120VAC transformer make much if any noise. There is a transformer in your power converter that steps down the 120VAC and then sends it through a bridge rectifier to provide the DC voltages the camper uses. If you’re certain it is coming from the converter/power distribution unit it is pretty much a remove and replace module.

I would go camping. Utilizing all systems on a camping trip, the problem may work itself out. No telling how long the camper has been sitting up if you just bought it and I’m assuming by you saying new to us it was used and no warranty is applied.

Before I bought a new power converter I would rule out all other possible sources of electrical noise. Might try turning off each of the 120VAC breakers that supply the systems one at a time to see if the noise changes. You can do the same isolation with the fuses too just make sure you secure power to the trailer and disconnect the negative battery cable before pulling or installing fuses. If the noise is still present with breakers off except main feed breaker and fuses removed I would look at replacing the converter module. This is just a rough guess since I haven’t actually heard the noise you’re describing. Good luck to you.

Thank you so much for the very thoughtful reply. Very kind of you, and it is appreciated. I will share this post with my husband.

[TakerEasy]

Good job finding that! Stuff like that can be pretty hard to locate at times.

Originally Posted by ricemanwm

Finally I had found the interment short.

[WeRJuliian]

Even small transformers can be noisy, if there's a loose bolt or maybe a lamination that's not fully secured.

Keep in mind that the noise will vary with the load*, so you may think you've isolated an issue by unplugging everything.. but what you may have done is just reduce the current flowing through the windings.


* My EE professor would be proud of me for recalling that... :-)

[ricemanwm]

Originally Posted by WeRJuliian

Even small transformers can be noisy, if there's a loose bolt or maybe a lamination that's not fully secured.

Keep in mind that the noise will vary with the load*, so you may think you've isolated an issue by unplugging everything.. but what you may have done is just reduce the current flowing through the windings.


* My EE professor would be proud of me for recalling that... :-)

Completely agree, reducing the current from the transformer could cause the noise to change giving a false indication of the source. Isolating the suspected source and then applying an equivalent load would help pin point the problem.

I’ve used a small piece of rubber hose in the past to help isolate an unusual noise. Crude but sometimes it helps; one end up to your ear and the other in the affected area. Extreme caution needs to be exercised when isolating a electrical noise on a live circuit though.

[pschriro]

Originally Posted by ricemanwm

The 15 amp fuse that protects the interior lights and exterior porch light along with the light under the steps of my 2017 265RLSW would blow intermittently. Completely driving me crazy because it was not a constant fault. Difficult to impossible to troubleshoot a potential short when the fuse was not blowing. Isolated it on a camping trip to the porch and step light; flip on the outside lights, fuse blows taking out living area lights as well. Kept the outside lights off for the trip and when I got the trailer home, no more blowing of the fuse and the outside lights worked perfectly.

Made a trip to Disney, no blowing of the fuse, bring the trailer home and finally the fuse blows at the house where I can isolate it. I’m careful not to disturb any wires while figuring this out; certainly don’t want the fault to go away. With the light switch off, I disconnect the connectors at the step light and read resistance between the wires supplying the power and return and perfect, I have a dead short. I follow the green 12VDC wire back and it was running under the bracket on the side of the fresh water tank. I remove the bracket and the wire is squeezed flat and right where it came out from under the bracket I saw exposed copper. Finally I had found the interment short.

Looking closely at the exposed copper, several strands were broken so I cut out the damaged area and put an inline splice, soldered it up, slid some heat shrink tube over it and problem solved. All the lights work, no more blowing fuses and the short is resolved. The bracket is not a support for the water tank but rather a positioning bracket to keep the tank from sliding around. Obviously I reinstalled the bracket without the wire running under it and to the side where all the other wires are running.

Just figured I would pass this discovery on in case someone else was battling with something similar. Wouldn’t be a bad idea to roll around under your trailer and look to make sure you don’t have any wires pinched between a bracket and the frame. Other discovery’s were wires running through bare holes in the frame, I use a small piece of heater hose, split it down the side and zip tie it so the wire insulation is not rubbing on the metal hole. It would probably take years of travel vibration to wear through the wire insulation but nothing wrong with some homemade grommets. The picture of the bracket is after the repair.

Good catch! I second your observations. We just took delivery of a 287 BHS about three weeks ago and when I was under the TT, I noticed that ALL of the wiring is exposed to the elements and is a potential victim to road debris.

Instead of heater hose, I'd picked up some wire loom conduit and wrapped the main bundle from the junction block to where the wiring enters the trailer just behind the fresh water tank on the right-hand rail. A few select pieces were position to protect wiring passing through frame cross members as well.

There are several sizes of conduit. I already had a roll of 3/8" and the wire fit, but 1/2" would be ideal.