Guardmaster headache

Working with Guardmaster 450L-B. Is there a distance too close for these modules to be mounted? These are about 20" apart. Can't get the safety outputs to come on and have checked everything thoroughly.

Yes there is a minimum distance. The distance is based in what the resolution of the light curtain is.
In the manual it calls out the distances. I think 24" is minimum. Dont hold be to that number. It has been several years since we had that problem.

450L-B:
Resolution 14 mm (0.56 in.): 0.5…4 m (1.64…13.12 ft)
Resolution 30 mm (1.19 in.): 0.9…7.0 m (2.95…22.97 ft)
Reduced operating range (selected with DIP switch):
Resolution 14 mm (0.56 in.): 0.9…2 m (2.95…6.56 ft)
Resolution 30 mm (1.19 in.): 1.2…3.5 m (3.94…11.48 ft)

So looks like 20" would be the min if using the 14mm version in normal range.