2670MK with 12 volts on the frame

[JeffnDeb]

De-winterizing the trailer. When putting the batteries back in, the ground wire off the battery slipped and hit the frame, where it sparked. Thinking that was strange, I got of the DVM and found that I have 12 volts between the battery negative and the frame?? I'm thinking this can't be right. The 7 pin doesn't seem to have any issues when connected between the truck and trailer. Also, the display in the trailer shows full charge on the batteries. I would have never known this because all looks good, except for when it sparked. No blown fuses, so I'm kind of thinking this might be normal??? Thx for any info.

***Update***
Took the trailer into town today to repack the wheel bearings. I got to looking at the truck connected to the trailer and thought that there was no way that +12V could be on the frame. I grabbed a different DVM and the frame now showed that it was grounded. I rechecked with my original DVM and it was still grounded. Not sure what happened last night to show a voltage potential on the frame. Now everything looks as it should.

Thanks for the inputs.