I have kind of the opposite problem, have 16V all the way through with multi-meter, even at the plug for the beacon, but neither the beacon or light work, checked the bulb, seems to be fine, not blown, checked the resistance at the beacon plug, there is some so connections are being made in either the motor or light, puzzled......

16.4 volts coming out of J104 all the way to the plug at the beacon motor and light.

If just the 1156 lamp is blown wouldn't the motor still spin? Found something like this problem on RGP but no answer

Replaced the 1156 bulb. Still no go.

ok, just going to run through it all, LED 5 is good, 20vdc on, 17v measured at J104, 17v measured all the way to the plug of the MARS lamp, problem is that it always measures this, even when not being tested, its like the voltage is always there, checked F111, good, checked R224, measure 7 ohms, (says 12 on it), don't know what else to look for

I have smacked it a few times thinking the bulb housing might have been touching and grounding it all out. Took the motor and bulb housing out and verified no accidental touching.