About the quickest way to look for a cause is to begin with a polarity tester. That will show if the outlets all the way to the trailer cord, are wired correctly. On a 3 wire outlet - the oblong is the ground for the green or bare wire, the shorter vertical slot is for the hot most times black, the longer vertical slot is for the neutral wire - most times white. I recently checked my brothers trailer, same as your problem - the outlet he plugged into in his garage, had been replaced and was wired wrong.
Ok, time to put on the thinking cap... 50, volts is within range for this.
you have a fairly long cord between the outlet and the coach, You need to do this
First, pull the plug,,, Measure not the voltage,but resistance between the "odd" pin on your power plug (The round or "D" or "U" shaped one, not a flat pin) and the chassis... Should like the test leads are touching each other
NOTE: do this UNPLUGGED
If the cord can be "Disconnected" from the rig, Measure end of cord to end of cord.. The "Green" wire is the outer edge of the inlet Plug. (Cord outlet) This is a good suspect if you got one.
Measure from the matching contact on the INLET to chassis (If you have an inlet)
If you get an "open circuit" indication, you have a broken ground wire, I'm guessing in the plug (Reasons later) but it could be anywhere. If the plug is removable, check inside it, if not do the same test at the other end of the power cord Now on many trailers the power cord goes straight to the circuit breaker box (Distribution panel) but on many motor homes it goes to an automatic transfer switch Test here, same test, Green wire (or bare wire) to ground.
Inside the breaker box INSPECT the connection between the main power cord (or the line from the ATS) green or bare wire to ground... I often say "Many RVers have a few screws loose" These screws (Inside the breaker box) are the specific screws I'm talking about when I say that. Check all screws since you have the box open and the plug pulled.
In all these tests save one, you are looking for the point where you suddenly DO have a connection to ground. (The one test is end-end on the power cord.
If you do not get end to end on the power cord.. Then you have a bad power cord, Likely on the plug end but anything is possible STOP now. Replace cord. (or re-end it)
If the power cord is good, Then keep going till you find a connection to the chassis, The bad spot is between ZERO and INFINITY (Short/open)
Now; where does the 50 volts come from
You have three wires laying side by side, at least 30 feet long, perhaps longer, Two pieces of metal seperated by insulation = a capacitor
These three wires are forming what is called a "Voltage Divider" circuit
True, 60 volts is 1/2 of 120, but there may be another... POOR.. Path to ground sucking it down just a bit, In fact even the load presented by the meter itself can do that since this is a very very low-current divider.
There is another way you can test that might be better.
Hook a long wire to your 12 volt positive, Other end to a light bulb (Standard "STOP/TURN" or "DOME" lamp type bulb, Use the other end of the bulb to probe for ground END of cord (I'll bet dark bulb) Inlet (if any) ATS (if any) Breaker BOX (i'm guessing bright bulb here) Just where you will "See the light" I can't predict, only the ends
The advantage of the light bulb method is it passes nearly an amp of current so it will show up a high resistance as well as a full open.
Nothin adds excitment like something that is none of your business John is Near Kenwood TS-2000 housed in a 2005 Damon Intruder 377
Well...I'm back from the bike ride only to have an interesting development....
I just took the multitester to the trailer again and I can no longer see any voltage between the trailer frame and the earth/ground. I also get normal readings on the external AC plug on the trailer. This has me scratching my head a little, but it gives me a thought....
When I left for my bike ride... I had 50 volts neutral->ground. When I came back, I get 0 volts on same reading. I changed nothing...trailer still plugged in same spot..same cords..same way.
My thought right now is the converter *might* have been on/charging the batteries earlier and maybe now it isn't. I'm not sure if this is the case, but it's the only thing in the trailer that is electrical in nature that I can think of which might have "changed" while between my readings/testing.... I know that now I'm not hearing the cooling fan for the converter running while I'm getting 0-volts neutral->ground...but I didn't pay attention earlier to know if it was running/cooling or not.
I'm also not sure that the cooling fan is a reliable indicator of when the converter is doing something like charging the batteries.
Thanks for all the feedback so far... I'll keep posting as long I as have something I think it useful to say. I'll let you know whatever I eventually find (assuming I do) as well.
Constructive disagreement is encouraged. It is how I/we learn!
Your 50 volts could be caused by a moisture short, I would be most concerned that the trailer is properly grounded. Measure from the frame to a metal stake in the earth. It should be a short on the ohmmeter. The water stream is not a good ground and could be misleading.
Turning off the AC breakers should isolate the short (High Impedance short). If it does not, suspect a pinched wire.
Your last post triggered a thought. You might have a nick in the cord also. the water acted like a conductor causing you to get a false reading. It might have dried out just long enough to make the short disappear. Was the cord laying in a puddle by any chance? Was it laying on snow covered ground?
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When you last plugged it in the corrosion on the ground pin was finally cleaned off
You might wish to finish the cleaning (unplugged of course)
Alternative: I mentioned a bad cord/plug connection (Bad cord likely at the plug) you may have "Wiggled" it enough to make it good again,, FOR NOW... Still needs investigation
If you are using a 30A to 15A adaptor check for an intermittent Ground wire through the adaptor. That happened to me one time, the male plug ground pin was not making the female ground on the 30A side of the adaptor
Harvard wrote: If you are using a 30A to 15A adaptor check for an intermittent Ground wire through the adaptor. That happened to me one time, the male plug ground pin was not making the female ground on the 30A side of the adaptor
I'll do some more poking around tomorrow..but this sound promising to me.
One thing that he electricians in the crowd might help me with though....
If the 30A->15A adaptor plug has a ground-pin that isn't making connection..... should a lack of connection to the ground cause the 50 volts I saw? Even without ground...shouldn't it be zero volts? I guess I'm thinking the ground is there as a safety feature...but shouldn't have voltage across it and neutral...
Truth is though, I don't know what I'm talking about when it comes to this stuff...I'm just making guesses from your feedback and a bit of google-searching...
Quote: .... should a lack of connection to the ground cause the 50 volts I saw? Even without ground...shouldn't it be zero volts?
The lack of a ground connection won't cause the 50 volt reading, but it will allow it. You mentioned the power converter earlier. Some power converters use the ground to absorb a small amount of current. It's less than what's needed to trip a GFI, but enough to energize an ungrounded chassis to feel a tingle. The amount of current can vary with the load on the converter: more current to ground when the converter has a heavier 12 volt load. This is normal (I'm not saying it's good, just normal) and, depending on which converter you have, could provide the explanation. The chassis could also be energized by something else that isn't normal, but whatever the case, if the chassis has voltage to earth ground, it's not properly connected to the earth ground.
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