The 3 wire photo cell is very durable, it can be miss wired in any configuration WITH OUT being damaged. Before replacing this device be sure that you have check the cell properly even if it means removing the P-cell and taking it to the panel and connecting it directly.
The 3 wire photo cells are only used on iDH/iDIM Micro Panels to trouble shoot a UPSI you need to know the following information about MP's. In the Scene under PC the P-cell reading for inputs 1-4 will read 1000 if there are not photo cells attached. If the photo cell is attached correctly and the P-cell is working then the appropriate read somewhere between 0-1000 will show.
The problem comes when the P-cell is not working there can be various difference readings. A reading in an iDH/iDIM panel of 1000 does not necessarily mean that there is no P-cell wired to the input it could be a miss wired p-cell. The normal reading for a micro panel without a p-cell is 1000 and this reading could also result from a p-cell that is saturated due to the placement and or miss a wired P-cell. You may also find that a miss wired p-cell gives you a reading of 0; in this case the readings on the other inputs will be drawn down by 0-160 points.
If a P-cell is wired to input #1 with the ground connected to the photocell input and the photocell output connected to the ground then the P-cell reading for #1 will be 0. If input #2-4 do not have P-cells attached to them then their reading will be pulled down from 1000 and will probably indicate somewhere between 840– 920. If there is another P-cell on one of the other inputs then its reading will also be low but you will not notice it.
A miss wired p-cell can give you different results. See the Chart:
SO if you see a reading on a photo cell input that is 0 and does not change when exposed to light check the other inputs, if any of these do not have a p-cell attached and it is reading between 840 and 940 expect that the photo cell is miss wired.