According to DerbyDad03 :
A co-worker, who should *not* be doing his own wiring attempted to add
a 2nd light fixture in his mudroom this weekend. Here is the situation
he presented to me this morning.

Light Fixture 1 (LF1) is an existing ceiling fixture in the mud room.
An existing Switch (S1) controls LF1.

He added LF2, a second ceiling fixture in the mud room, and wants to
control it with S1.

LF1 holds an incandescent bulb and LF2 holds a compact fluorescent.

He took the cover off of S1 and found a black and white from length of
Romex attached to S1. That's all that was in the box. So far, nothing
out of the ordinary, as far as I can tell. I'm assuming this length of
Romex is the switched hot from LF1.

It's the hot and switched hot. _No_ neutral. This is a switch leg,
you can't get "proper" power from the switch end of this circuit.

When S1 is on, LF1 will be on, but the leads to LF2 are shorted
by the switch. When S1 is off, LF1 and LF2 are in series. Since
LF2 is a CF, it's current draw is very low, and it lights up, but
the current is insufficient to visibly light LF1. If LF1 and LF2
were identical incandescent bulbs, they'd both light dimly. If
they were both CFs, can't predict precisely what they do without
knowing what the CFs do with 60V. Might not do anything.

He needs to take the wire from LF2 off S1, and move it to be
across the leads on LF1 (inside the LF1 junction box). Eg:
LF2's black wire wirenutted to the wire going to the center
pin on LF1's bulb base, and white wire wirenutted to the wire
going to LF2's base shell. Then the voltage seen on both
bulb bases will be identical.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.