50A power problems
A guided diagnosis for RV techs. Each step is a check, a reading or a question.
- 50 A service: what is wrong? A 50 A coach has two 120 V legs. Meter the pedestal first: each hot to neutral 120 V, hot to hot 240 V, neutral to ground 0 V. Expect: 120 / 120 / 240 at the pedestal
- Where does the second leg disappear? Meter both hots at the pedestal, then at the coach end of the cord, then at the transfer switch output, then at the panel. Expect: Both hots 120 V at every point
Causes and repairs
Pedestal missing a leg
One pedestal breaker tripped or a park wiring fault. Not your coach.
Tools: multimeter
Reset the pedestal breaker. If one leg is dead, have the park fix it or move.
Burned blade on the cord or inlet
One hot blade on a 50 A plug ran hot and burned. Look at the plug face and the inlet.
Tools: flashlight
Replace the plug or inlet. Check the inlet's terminal screws.
Transfer switch dropped a leg
One set of contacts burned or a terminal loosened. Common.
Tools: multimeter
Tighten terminals. Replace the switch if the contacts are pitted.
Main breaker lost a pole
A two-pole main with one dead pole.
Tools: multimeter
Replace the main breaker.
30 A adapter feeds both legs from one 30 A line
A 50-to-30 dogbone puts the same 120 V leg on both sides of the panel and limits you to 30 A total. Everything works, but two ACs plus a water heater will trip the pedestal.
Tools: none
Manage loads. Nothing is broken.
Pedestal wired with the same leg on both terminals
0 V between the hots means both are on the same phase. A park wiring error. The coach works but a 240 V appliance (rare in RVs) won't.
Tools: multimeter
Report it to the park. The coach is fine.
Stop: heat at the plug or inlet
A melted plug is a loose connection that has been arcing. Unplug and let it cool.
Tools: flashlight
Replace the plug and the inlet together if either shows heat. Torque the terminals. Check the pedestal receptacle for burned contacts too.
Keep going on 120V and shore power
Learn it
- Shore power: 30A vs 50A
- Breakers, GFCIs and the EMS
- The lost neutral (50A danger)
- Transfer switches and generator power
Prove it
- Half the coach is dead
- Bathroom outlets are dead
- Lights surge and the microwave died
- Shocked at the door handle