AFAIK, the Gossen Pilot II is the (USA version) of the Gossen Sixtino which was sold under this last name only in Europe.
This meter usuallly gets the coil too loose on the pivots, so there is something tricky to do:
Look carefully to the coil/needle assembly. Tilt the meter left to right, slowly, several times, check if the coil keeps allways the same position related to the magnet. If the coil tilts a little, you will have erratic movements of the coil/pointerl, or no movement at all. The adjustment requires a lot of patience and care. To obtain good results, coils play angle should be almost zero.
You will see an aluminum frame wich is coil´s core. Inmediately underneath it, there is a small star shaped nut. This is the adjustement of the coils pivots height.
Usually the coil doesn´t go off the pivots completely. It will take one or two turns (hopefully, I don´t remember if this is a left thread or right thread nut) clockwise to regain the original position. Take extreme care not to bend the spiral, avoid absolutely touching coil wires. To drive this nut, use a very small thin pointed tweezer. Work carefully as it is an extremely delicate mechanism. Next step, repeat tilt check. If everything works, next step is to check the meter against a known meter.
If this did not solve the problem, do as follows.
The selenium cell is connected to the meter by two naked thin wires, one comes right from the back of the cell and goes to a small soldering copper tab in the left of the meter. This goes to the moving coil through the tiny spiral thats located in the uppermost position over the coil itself. The other wire comes in from the front of the cell (the area that will be illuminated) and is connected in series with several resistors (all in series) which make the calibration of the instrument.
There is another element and is a thermistor, which is connected in paralell with one of the two other resistors. This compensates cell output variation caused by temp. changes.
Check with a DMM (digital multimeter) if the cell gives a steady output voltage under constant lighting conditions (use any light bulb available to check it). Check if there are no other loose connectionas. Be sure the screw at left (which holds the instrument in place) is tight, as it serves to connect the resistors to the meter. In case the cell is disconnected frn any wire, do not try to resloder it. The soldering iron may remove completely the extra thin silver or gold coating used to attach wires to the cell. Replace the cell in that case.
Check if anyone of the resistors is broken (extremely unusual).
If nothing of this works, place a 3,3 Kiloohm resistor in series with the DMM positive lead, set OHMs check in the range of 2,0 Kiloohms. Place the DMM leads across the coil connections and check if there is any deflection of the instrument. If no deflection....tough luck...you have to make the coil checked/repaired by an instrument technician, or to look for another Pilot II to get spare parts.
Good luck! and if you need anymore info or help, please email me!
Ernesto