power surge on a/c compressor wire with all fuses off

I agree if 120vac is getting to the Roof with all breakers off you have a problem, Suspct follows

But there is also 12 volt to the roof for control purposes.

Now. the suspect
Is yours a 50 amp RV or a 30? on 30 amp models WITH A GENERATOR and automatic transfer switch power to the air conditioner may be run though the Auto Transfer switch and one of the breakers on the generator (the 20 amp one we hope).

Possible suspects:
Idiot electrician at factory
Bad ATS

Perhaps 50a service,as in a second breaker panel somewhere?
Art.

affenqld wrote:

j.p.f. wrote:
couldn't a large charged capacitor show a presence of electricity with all the power shut off?

I am sorry , i am not mechanically inclined , and i have no idea of what is a capacitor is ....aaarrrghhhh
What i know is that electricity runs in the wire of the compressor while all breakers are off , had to unplug trailer from shore power for them to work on the A/C
They have checked if power comes and leaves the breakers when they are off , and for sure they can read power in the breaker box after everything is turned off ..
Puzzling for me because i cannot comprehend anything with power ..lol.
More puzzling for them because it is their field of work ..lol.

1. IF the only way to get NO 120 power to the AC compressor is by disconnecting the Shore Power---SOMETHING is WAY WRONG WITH YOUR 120 SYSTEM. WITH THE 20 AMP AC BREAKER OFF THERE SHOULD NOT BE 120 POWER TO THE AC AT ALL. Regardless of any other box or 120 distribution system in your RV. If you have 120 power to the AC with the 20 amp breaker off that is a major problem.
2. The burnt wire if ON the AC upper Circuit Board and the black compressor relay, that usually points to a BAD locked up or shorted compressor
3. The statement "Power Surge". HOW do you determine that to use that statement. HOW do you "see" or hear a Power Surge??????? Especially with the power system OFF? If the burnt wire is hitting a neutral or ground, then I could understand a noise. BUT, they should have cut the offending wire OFF and retested.
4. Last, IF the Compressor relay on the upper Control board is burnt/ fused CLOSED, then yes, you will get constant 120 power to the compressor and if the compressor is bad, will eventually burn/melt that wire. The Compressor failed and heated up and fused the Compressor relay closed and the heat build up melted the wire. BUT NOT IF THE 20 AMP BREAKER IS OFF. Doug

j.p.f. wrote:
couldn't a large charged capacitor show a presence of electricity with all the power shut off?

I am sorry , i am not mechanically inclined , and i have no idea of what is a capacitor is ....aaarrrghhhh
What i know is that electricity runs in the wire of the compressor while all breakers are off , had to unplug trailer from shore power for them to work on the A/C
They have checked if power comes and leaves the breakers when they are off , and for sure they can read power in the breaker box after everything is turned off ..
Puzzling for me because i cannot comprehend anything with power ..lol.
More puzzling for them because it is their field of work ..lol.

dougrainer wrote:
Your puzzled and the tech is also???? You need to explain
1. How with power off you could get any power at all
2. There is NOTHING-NOTHING in the RV or appliances that can cause a Power Surge
3. WHAT is the problem with the AC system?
4. The system uses 12 volts to power the AC controls. The 120 is just to run the Fan Motor and the Compressor
5. Why was the tstat replaced? Failure of a tstat is rare
6. 10 years old, did he replace the burned out compressor wire? WHERE was it burned? At the 3 pins on the compressor or at the Circuit board relay? Doug

Power off , still electricity in the compressor wire
Problem with the A/C system , is that the compressor wire in the box relay burns down , so the compressor does not start
Thermostat and converter box replaced in march 2016
A/C unit is a 2015 dometic heat pump
Thank you for your help , it indeed is very appreciated
Affen

Power is present with all breakers off , electricity is still present with all breakers off .
Compressor wires receives power with all breakers off , the only way to eliminate power is to input trailer from shoreline power

They are puzzled because with all breakers off including the master breaker , they is still power going thru the wires of the compressor
A/c is almost new (2015),the wire which burned in the compressor box relay , as I have seen them opening the box .
The fan runs , but the compressor does not start because of the burned wire ..After being getting jolted by the power while touching the wires after all breakers were off , we had to disconnect the shore power from the trailer ...
They say it should be another box somewhere in the trailer where wires meet before to reach the breakers box ..
You might know where I could get the electrical diagram for this trailer , Dutchmen has not been very helpful so far ..
Thermostat was changed in March 2016
Converter was changed in March 2016
They have tested if power comes to the breakers after everything is off , and it does ...
They also told me that the compressor was damaged because of that burned wire.., it draws 16 amp at start , they told me the compressor is in way out , but it just turned 2 years .
I have this repair company maintaining that trailer for the last 10 years , every 6 months they come and check everything , they are the one who installed new a/c , converter and thermostat .
That trailer was never on the road , it came from the dealer directly on my lot ...
I am not mechanically inclined , so I am at their mercy ..
Thanks you for all your help , it is so appreciated
Affen

couldn't a large charged capacitor show a presence of electricity with all the power shut off?

Your puzzled and the tech is also???? You need to explain
1. How with power off you could get any power at all
2. There is NOTHING-NOTHING in the RV or appliances that can cause a Power Surge
3. WHAT is the problem with the AC system?
4. The system uses 12 volts to power the AC controls. The 120 is just to run the Fan Motor and the Compressor
5. Why was the tstat replaced? Failure of a tstat is rare
6. 10 years old, did he replace the burned out compressor wire? WHERE was it burned? At the 3 pins on the compressor or at the Circuit board relay? Doug

You will need to trace the source of the power that is feeding the compressor through that wire. Typically, with all circuit breakers off, this would not be possible. I would start at the load center since that is the junction for all 120V and 12V wiring.

BTW, I assume when you say "surge", you are actually meaning that power is present, not an over-voltage situation. That is a different problem, entirely.