class "a" wiring???. you should be able to see the 4.7k e.o.l definetly not per nfpa 72 if it's wired like that.
i can understand if they series the two 2.2k ohm resistors to make it close to 4.7k. is the circuit in question coming out of the same port of the power supply???? 2 wires out or 4 wires out???
if you cant , there is something seriuosly f*(ked up! is it just a horn circuit or a horn stobe circuit????
you should have the equivalent of 2 thhn stranded pair for your horns and a fplr solid for your strobe circuit. or you can take a 12 volt battery and take the loop off of the p.s. and test it.
if you are not seeing the e.o.l , that circuit is not being supervised.
also break the circiut in half and read the e.o.l, double check your circuit to make sure you are on the correct set of strobes.i have seen so much shitty installs in my life to say to you , rip it out and run it right. it is after all life ,safety issue.
what kinda equipment????????notifier, siemens,est,etc........
meat