truck gets no power when sylenoid crossed

[Boggin]

well i removed a plate on the chassis thinking the filter was behind it, when really it was the other pump, so after i got it off i figured id put the compressor up to it anyways to get some snot out, and i did so and hooked it back up and when i cross out the sylenoid now its like she looses all power then wen i release the screw driver the pump cuts in again. battery is charged, and i changed the sylenoid twice, and still the same, only this time at least when i turn the key i hear a 'click' sound, but i turned on the headlights and i tried crossing her out and the head lights went out, so she looses allpower when she is crossed out
any ideas?
thanks guys