Ok, i did some tests and I am so much lost than before jaja.
Follow the recommendations, the erratic behavior happens from a cold start with low water in the boiler..so the premises are:
1_It fails from a cold start
2_Clear continuity between boiler and Ground. (Ok)
3_No continuity between level Cable and probe to boiler or ground. (Ok)
Disconnect from Control Box the 2 output hots, they came from relays activating motor and selenoids.
Result: The relay activating ok and steady with no erratic behavior (no flickering on and off)
So water level is working ok and control box too.
Connect the output hot going to Motor and Selenoid in the control Box and disconnect the output water Pipe directly from the motor to bypass the selenoid.
Result: The relays activating ok and the water flowing to a reservoir.
Ok, motor works ok, let's see the selenoid.
I connect the output motor water pipe to selenoid.
Result: erratic behavior with relay and motor flickering on and off.
...Well is the selenoid.
Turn machine one, flickering starts, disconnect cable from level probe and... !!!flickering go off and the boiler fills awesome!!
This test blow my mind away.
Conclusions so far with this tests:
1_Level Prove ok, grounds ok
3_Selenoid (ok when grounding cable probe with boiler, error when grounding probe with water??)
4_Control box ok(relays activating ok, flickering in closed system/normal machine operation)
5_Plumped Pressure water in line problem? It seems not, with all the circuit closed and grounding the cable to boiler it enters to boiler, so in water pressure ok.
I'm really lost, doubt is a joy given from god