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jniblack's avatar
jniblack
Explorer
Apr 21, 2015

No AC power when plugged into a good AC shore power source?

I am having an electrical issue in my 2012 Puma Unleashed 356QLB 5th wheel toy hauler. I was camped at Little Sahara last weekend and was on shore power with things working like normal. It had rained hard Thursday night/early Friday morning, and again Friday/Saturday. Don't know that is related in anyway, but mention it in case. Around 10pm Saturday night I took a shower. Just as I was getting out of the shower I heard the TVs go off, and my kids started saying their phones weren't charging (that is a whole different thread..) I knew a band was setting up and just starting so I assumed they tripped a major circuit or something and just kept getting dried and dressed. When I went out I noticed all the other trailers around me had lights on and no one was outside checking their posts. My lights were still on, but I know they are DC and have 2 good batteries fully charged. My microwave was not working. I plugged an extension cord into the post that lights up when it has power, and it lit up. I also plugged into the neighbors post, and still nothing. If I run the generator, AC power is restored and the microwave and things work. I verified again today at home on a known good 120v AC 30A circuit. I'm not the most familiar with RV power systems. What could cause a loss of AC power when plugged into shore power, but AC power works with onboard generator running? With generator on, I see a voltage increase to the batteries so assume the inverter is working.. also not sure that relates in any way since AC power is not working.. Could my shower be at all related? The most concerning thing to me was when I was looking things over I removed the covers from the batteries. Ontop of one was what looked like the beginnings of a rats nest.. but there are NO droppings of any kind. Just as small pile of little pieces of stuff..?? Not sure if something got chewed through..? Remember power was working normally Thursday, Friday and most of Saturday. Nothing popped, that I heard, but I was taking a shower.. Just not sure where to start. Any pointers appreciated!

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  • jniblack's avatar
    jniblack
    Explorer
    Apr 22, 2015
    wa8yxm wrote:
    That will take out a lot of outlets but generally not the Microwave or Air Conditioners.

    I have found many an RVer has a few screws loose.

    On my rig ONE of the screws on the power inlet (Where the cord connects to the RV) was loose.. Just one.

    On a brand new 5er that was once parked in front of me all SIX of the screws inside the Marinco outlet (The part that plugs into the RV) were loose.. The outlt fell off in my hand when we went to figure out what the problem was.

    I'd have loved to be there when he visited his dealer next. :).


    ^^ This! After work today I removed the panel holding the breakers and fuses. Attached to the backside was a silver box as described above. I removed the cover to find two sets of wires coming in, one labeled shore, the other generator. With shore power plugged in I checked voltage on the hot (black) wire coming from shore. I had no voltage reading. I then fired the generator and checked voltage on that hot wire and had 120V. My camper has a power line that plugs/twists to the rig, and plugs to shore on the other end. I also use a 30Amp extension cord that lights with power. I checked at the lighted end, 120V, then plugged the camper cord in and checked the side that twists onto the rv. Was getting and odd 19-20V reading. Checked and one of the three screws was loose. I tightened it, plugged things in and it works. Not sure if I should consider replacing the cord or not?

    Thanks again everyone for the quick and helpful responses. Nothing like solving a problem without spending a dollar and learning something in the process!
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Apr 21, 2015
    I NEVER built a rig for me or friends that did not have two pilot LEDs on incoming power. Three, if an automatic transfer inverter was incorporated. A bridge LED connected between incoming and load was red and it stuck out like a sore thumb if a circuit went open. Do these modern gizmos use mechanical relays or SCRs?
  • Bobbo's avatar
    Bobbo
    Explorer II
    Apr 21, 2015
    Camreal wrote:
    Had a problem like that several years ago. After a heavy rain I had no AC on one side of the trailer. Problem turned out to be the GFI in the bathroom kicked out and lost AC on that side of the trailer. Check your GFI .

    The fact that everything runs fine off the generator rules this suggestion out.

    I go with everyone else and say check the ATS. My rig has no ATS and I am happy about that. My generator runs to an outlet in my electrical compartment. If I want generator power, I unplug from the pedestal and plug into that outlet. If I ever buy a rig with an ATS, that is what I will put in when, not if, it fails.
  • jniblack's avatar
    jniblack
    Explorer
    Apr 21, 2015
    Thanks for all the responses! I'll start by chasing down where the transfer switch is after work today.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Apr 21, 2015
    That will take out a lot of outlets but generally not the Microwave or Air Conditioners.

    I have found many an RVer has a few screws loose.

    On my rig ONE of the screws on the power inlet (Where the cord connects to the RV) was loose.. Just one.

    On a brand new 5er that was once parked in front of me all SIX of the screws inside the Marinco outlet (The part that plugs into the RV) were loose.. The outlt fell off in my hand when we went to figure out what the problem was.

    I'd have loved to be there when he visited his dealer next. :).
  • Camreal's avatar
    Camreal
    Explorer
    Apr 21, 2015
    Had a problem like that several years ago. After a heavy rain I had no AC on one side of the trailer. Problem turned out to be the GFI in the bathroom kicked out and lost AC on that side of the trailer. Check your GFI .
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Apr 21, 2015
    YEP..........

    Transfer switch

    It is what allows 2 different AC power sources to be wired to power your RV.

    Shore power has failed and transfer switch is swapped to generator side. That is why you get AC power with generator running.

    It is a metal electrical box with 2 sets of wires going in (1 from shore power cord/1 from generator output) and 1 set of wires coming out (going to main AC Panel).

    It could be behind a panel......need to trace power cord to locate.
    Could be burnt/loose wiring or bad relays/contacts

  • Happy_Prospecto's avatar
    Happy_Prospecto
    Explorer
    Apr 21, 2015
    It sounds like your transfer switch went bad. It transfers 120 volt power so your trailer can be fed with power from shore power or from your generator. When my transfer switch went bad I could only power my trailer with the generator.

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