15 Amp 12 V fuse randomly blows w no activity (or not)

[Bob Chamberlin]

Bob and Katy C
2017 Solitude 310GK purchased used in 2021
2011 Ram 2500 w B&W Companion

Original owner said "there is an electrical leak - carry some 15 Amp fuses". (I have a bag of 50). Circuit controls 12 V control signals to Heat Pump, Refrigerator, Gas Furnace, includes Thermostat and CO/Propane detector plus 2 LED lights near refrigerator. Frequency of fuse blowing varies from "immediate and repeated" to up to 2 months and everything in between. Will blow when nothing is being used, trailer static, no wind blowing or occasionally when traveling. Has been known to not blow all the way from Seattle to Phoenix and back but then to blow repeatedly (4 in rapid fire sequence) while camped. In that case, let it just sit for three hours and new fuse then worked fine for 6 hrs. but could not keep it operational at all for the next several days while traveling (no Refrigerator and no Furnace in late October). Since then, . . . . Will blow with Shorepower connected only, battery power only or both connected. Have replaced Thermostat and disconnected CO/Propane detector. Fuse still blows randomly but it lasted for 2 months after Thermostat replacement. Meanwhile, varied using Heat Pump, Refrigerator and Furnace in various combinations and none at all. Fuse finally blew with nothing operating except the Thermostat for no apparent reason. Have used Clamping Ampmeter but never more than 1.4 Amps with everything running. Tried moving circuit to a blank location on the fuse panel. Didn't help. Currently tearing into Furnace to look for a potential short. Any thoughts?

 

[Ynot4me2]

Those are hard to pin point and find. Sounds like either a loose wire or frayed. Is it always the same 15amp fuse that's blowing?

 

[Bob Chamberlin]

Thank you so much for your very quick response. It is appreciated. Yes, there is only one 12 V circuit that has a problem. (Always the same fuse slot.) Have opened the Furnace (which was very dirty). Vacuumed and cleaned it all out and found a frayed wire next to a metal structural member. Re-routed the wire and covered it with heat-shrink tape. All working fine but based on history this may not be a fix. The problem has NOT been consistent and has been known to happen randomly when nothing was moving in the trailer and no appliances were running. That does not mean that the Furnace was not trying to come one when the fuse blew so I will have to just wait and see. Thanks again for responding.

 

[triplethreat]

Thank you so much for your very quick response. It is appreciated. Yes, there is only one 12 V circuit that has a problem. (Always the same fuse slot.) Have opened the Furnace (which was very dirty). Vacuumed and cleaned it all out and found a frayed wire next to a metal structural member. Re-routed the wire and covered it with heat-shrink tape. All working fine but based on history this may not be a fix. The problem has NOT been consistent and has been known to happen randomly when nothing was moving in the trailer and no appliances were running. That does not mean that the Furnace was not trying to come one when the fuse blew so I will have to just wait and see. Thanks again for responding.

The location that you found the frayed wire......did you see any signs of arcing in that area? If that was it, as many times as you have replaced the 15A fuse, there would definitely have been blackened spots where the wire arced repeatedly.

 

[jkwilson]

A trick from the old days that can help locate loose or intermittently shorted wires is to use an AM radio. Tune it to a space where there is no station. Jiggle, shake, pull etc. on any wires or components connected to or near the suspect wire. Electrical arcing produces strong, broadband RF signals and the radio will produce a sound similar to the way lightning did back when people listed to AM. It can be a great tool to narrow down a mystery problem.

 

[Scott'n'Wendy]

Well after examining all the wiring I could...I would buy a package of fuse holders and fuse everything at 5 amps. If the 15 still blows, it's in the supply wiring. If a 5 blows...you know where the issue is.

 

[stroguy]

Never more than 1.4 amps with a clamp on begs to ask why a 15 amp protector? I would rig up an inline multimeter for amps with some extension wires and alligator clips. Then start turning things on and watch the amp meter. Bang doors and roof panels and jiggle your 12V appliances and systems on that leg. I would think the 2 LED lights would draw more than 1.4 when on. Are they puck style?

 

[LMagelitz]

Well after examining all the wiring I could...I would buy a package of fuse holders and fuse everything at 5 amps. If the 15 still blows, it's in the supply wiring. If a 5 blows...you know where the issue is.

[MENTION=51970]Bob Chamberlin[/MENTION] I’d do what @Scott’n’Wendy says. I use this on grain drying LP heaters to find bad components when I get a frustrating intermittent fuse blowing issue. Works good.

 

[llr2800]

Never more than 1.4 amps with a clamp on begs to ask why a 15 amp protector? I would rig up an inline multimeter for amps with some extension wires and alligator clips. Then start turning things on and watch the amp meter. Bang doors and roof panels and jiggle your 12V appliances and systems on that leg. I would think the 2 LED lights would draw more than 1.4 when on. Are they puck style?

Not a bad idea but the fuse will probably blow quicker then the meter reacts.

I suggest connecting a 12v incandescent light (old school taillight) in place of the fuse. Then bang shake move everything you can. The light may be on an dim until you trigger the short, then it will be bright. The more you can trigger the bright bulb the closer to the issue.

Of course hopefully the wire you found by the furnace is the issue and you are done.

 

[traveldawg]

I’d be separating out some of those loads onto their own circuits. It sounds to me like a lot of loads for one circuit. Similar to the 15 amps GD provided up to my control panel for soooo many things. Onc e I split the loads onto 2 circuits - no more issues.

 

[stroguy]

Not a bad idea but the fuse will probably blow quicker then the meter reacts.

I suggest connecting a 12v incandescent light (old school taillight) in place of the fuse. Then bang shake move everything you can. The light may be on an dim until you trigger the short, then it will be bright. The more you can trigger the bright bulb the closer to the issue.

Of course hopefully the wire you found by the furnace is the issue and you are done.

My meter has a hold function to snapshot the highest reading(s). Guess I should have added that function is helpful. If doing the checking solo.

 

[Bob Chamberlin]

Thanks for your thoughts. Very much appreciated. All of the appliances in question are powered by either gas or 110 V AC. The 12 V circuit in question only provides enough power for control signals and ignition spark for the refrigerator and furnace (other than a couple of never used LED puck lights so I am doubting that the circuit is overloaded. That said, it appears that the problem is likely resolved although I will remain skeptical. A bare spot on a wire next to a frame member at the furnace has been found, repaired and re-routed. I won't know for sure until a lot of time passes with no more problems in the circuit.

 

[Mr. Goodwrench]

Thanks for your thoughts. Very much appreciated. All of the appliances in question are powered by either gas or 110 V AC. The 12 V circuit in question only provides enough power for control signals and ignition spark for the refrigerator and furnace (other than a couple of never used LED puck lights so I am doubting that the circuit is overloaded. That said, it appears that the problem is likely resolved although I will remain skeptical. A bare spot on a wire next to a frame member at the furnace has been found, repaired and re-routed. I won't know for sure until a lot of time passes with no more problems in the circuit.

Hopefully your problem is solved. For the rest of us, this thread has provided a wealth of troubleshooting tips.

 

[ScottK]

An exposed wire getting wet can cause that. Even just a cut end.

 

[ExNihilo]

Just by chance is that a 12v refrigerator? Some were installed with a smaller gauge wire which typically blow the inline fuse to the fridge. If it is a 12 VDC fridge look at the wire gauge.

Apologies, I did not read all threads- I see they are 110v

 

[Haznavy]

Bob,

I'm having this exact same issue. What did you end up finding out and what was your fix?

 

[Second Chance]

Bob,

I'm having this exact same issue. What did you end up finding out and what was your fix?

[MENTION=51970]Bob Chamberlin[/MENTION] hasn't logged into the forum since January. Quoting someone (as I have done with you here) or tagging someone (as I have done with Bob Chamberlin) will generate an email notification that they might see.

Rob

 

[Bob Chamberlin]

Thanks to the many people who have responded to my initial Post. Since I did not see any responses in the first week or two I stopped looking at this forum. For those who have asked, this is to explain what my resolution has been. My problem was with a single 12 V fuse randomly blowing when there was no motion of any kind in the trailer (or when it was going down the road). IE: No predictably repeatable cause. First, I found a frayed wire brushing the frame of the gas heater. Fixed it with heat shrink tape and re-routing but that turned out to NOT be the real problem cause. In my initial post I said that the items on the affected circuit were, 1) refrigerator (which is 110 V and/or gas) but which has control signals using 12 V, 2) thermostat (meaning that control signals to the gas heater and both AC units were unavailable), 3) CO/Propane alarm. My thinking was that any of these items could have been the problem or it might be a wiring problem. Without a refrigerator or a gas heater the trailer was unusable especially in the winter months. Following my initial post I also found that the right rear brake/turn signal light was out and replacing the LED fixture did not fix the problem. Replaced the thermostat (yes, they do break down anyway after five to ten years). Did not fix the problem. Disconnected the CO alarm. No help there either. Found that there was a significant hydraulic leak near the right side center jack. Note that this had nothing to do with my 12 V problem but I had to fix it. Had to remove the underbelly. Replaced the fluid soaked insulation and found that Grand Design had installed the hydraulic line in direct rubbing contact with the rotating slide gear mechanism. Re-routed the line and replaced it with a 20,000 psi dump truck hydraulic line. This powers both living room and kitchen slides. The reason why this is all relevant to the 12 V fuse problem is that while in the underbelly I found a 12 V electrical line that was routed such that it was repeatedly "pinched" by the Kitchen slide mechanism. Replaced a section of the 12 V line and re-routed it. ALL SYSTEMS NOW WORK PERFECTLY. Note: When I reconnected the CO/Propane alarm it acted very "flakey" so I have replaced it and now all is well. (There is a printed message on the CO alarm that it needs to be replaced every five years anyway.) Summary: I blame Grand Design for two assembly issues. One was the hydraulic line that was rubbing on the slide mechanism and the other was an electrical line that was being pinched by a slide mechanism. Other than that I am otherwise delighted with the design and construction of my 310GK. One last note: The power converter (which converts 110V power to 12V to charge your batteries and power many systems in the trailer died. Fairly new GSM batteries died. (They do not like to go all the way down.) Replaced power converter and installed new batteries. NOTE: Local RV repair person indicated that Power Converter failure is more common than it should be. Knowing this it is hard to understand why it is so difficult to get to the location in which the Power Converter is installed. Replacement took me two days.

 

[Haznavy]

Thanks to the many people who have responded to my initial Post. Since I did not see any responses in the first week or two I stopped looking at this forum. For those who have asked, this is to explain what my resolution has been. My problem was with a single 12 V fuse randomly blowing when there was no motion of any kind in the trailer (or when it was going down the road). IE: No predictably repeatable cause. First, I found a frayed wire brushing the frame of the gas heater. Fixed it with heat shrink tape and re-routing but that turned out to NOT be the real problem cause. In my initial post I said that the items on the affected circuit were, 1) refrigerator (which is 110 V and/or gas) but which has control signals using 12 V, 2) thermostat (meaning that control signals to the gas heater and both AC units were unavailable), 3) CO/Propane alarm. My thinking was that any of these items could have been the problem or it might be a wiring problem. Without a refrigerator or a gas heater the trailer was unusable especially in the winter months. Following my initial post I also found that the right rear brake/turn signal light was out and replacing the LED fixture did not fix the problem. Replaced the thermostat (yes, they do break down anyway after five to ten years). Did not fix the problem. Disconnected the CO alarm. No help there either. Found that there was a significant hydraulic leak near the right side center jack. Note that this had nothing to do with my 12 V problem but I had to fix it. Had to remove the underbelly. Replaced the fluid soaked insulation and found that Grand Design had installed the hydraulic line in direct rubbing contact with the rotating slide gear mechanism. Re-routed the line and replaced it with a 20,000 psi dump truck hydraulic line. This powers both living room and kitchen slides. The reason why this is all relevant to the 12 V fuse problem is that while in the underbelly I found a 12 V electrical line that was routed such that it was repeatedly "pinched" by the Kitchen slide mechanism. Replaced a section of the 12 V line and re-routed it. ALL SYSTEMS NOW WORK PERFECTLY. Note: When I reconnected the CO/Propane alarm it acted very "flakey" so I have replaced it and now all is well. (There is a printed message on the CO alarm that it needs to be replaced every five years anyway.) Summary: I blame Grand Design for two assembly issues. One was the hydraulic line that was rubbing on the slide mechanism and the other was an electrical line that was being pinched by a slide mechanism. Other than that I am otherwise delighted with the design and construction of my 310GK. One last note: The power converter (which converts 110V power to 12V to charge your batteries and power many systems in the trailer died. Fairly new GSM batteries died. (They do not like to go all the way down.) Replaced power converter and installed new batteries. NOTE: Local RV repair person indicated that Power Converter failure is more common than it should be. Knowing this it is hard to understand why it is so difficult to get to the location in which the Power Converter is installed. Replacement took me two days.

Bob,

Thanks for the detailed description of things to look for. My problem, thankfully, was chalked up to a rather sizable rat who managed to get himself lodged between the heater fan and housing causing the fan to seize and blow the fuse. Removed the rat, fixed the problem. If only all our problems could be fixed so easily.