50 amp power cord plug replacement

[namvet]

I have just replaced the plug on the 50 amp power cord of my rig. I have verified that the legs are wired correctly and that the connections to the lugs of the plug are tight. I have the rig connected, via an extension cord and adapters, to a 20 amp circuit in my garage and only use the power to keep my batteries topped off when not on the road. I have a voltage meter installed inside the rig. After my plug installation, I plugged the extension cord in and went inside the rig to check the voltage in order to verify the installation. I initially got a voltage reading of 120v but suddenly it dropped to 110v. There are no loads connected inside the rig and the 12v load center is turned off. Prior to changing the plug, the voltage meter always read a steady 120v when plugged in to this "shore power" arrangement and have verified that 120v is present at both the garage outlet and at the female end of the extension cord. I can hear the transfer switch engage when I connect the extension cord. When I check the power with the generator running, I get a steady 120v reading. I'm hoping someone can give me an idea what I have done wrong and how to fix it! Any help would be appreciated. Thanks!

[namvet]

Thanks to all for the responses. Dutch_12078 and wa8yxm, I think you have the solution! I checked again this morning in cooler temperatures and the voltage is holding at 120v. I am using a 25 foot 14Ga extension and I think that, in combination with the temperature and possibly the converter drawing extra current for the batteries, caused the drop. It really had be puzzled and, when the engineer in me kicked in, I visualized all sorts of potential problems. Thanks again to all!
Guy

[wa8yxm]

Dutch_12078 wrote:
Maybe your converter/charger is "shifting gears" as the battery charge state changes, increasing the current draw and the voltage drop through the extension cord. What size are the extension cord wires and how long is it?

I agree when my batteries are HUNGRY my converter can suck 1,000 watts, or more (10 amps) and if you have a long 14 Ga Extension cord (some are 16) between the adapters and the outlet.. 10 volts is nothing.

[newlee]

Is your water heater on electric

[drsteve]

namvet wrote:
Prior to changing the plug, the voltage meter always read a steady 120v when plugged in to this "shore power" arrangement and have verified that 120v is present at both the garage outlet and at the female end of the extension cord. I can hear the transfer switch engage when I connect the extension cord.

I would take the plug apart and redo all the connections first.

[Dutch_12078]

Maybe your converter/charger is "shifting gears" as the battery charge state changes, increasing the current draw and the voltage drop through the extension cord. What size are the extension cord wires and how long is it?

[time2roll]

Just need to move the meter up the wire to each connection and see where you lose voltage. Maybe just wiggle and reset the connectors.

However I would first check the common duplex you are plugged into to verify the supply voltage is not sagging. Check with the RV still plugged in.