Horn relay issues

[Bwword]

I need a little advice regarding the horn relay on my 1973 charger - I have been attempting to place an aftermarket radio (reproduction of the original) in this car, but I have now had to replace two horn relays and am in the process of ordering a third.  The battery is disconnected when working on the wiring. The car will not start without a functioning relay.  I have realized that the black wire on the original radio harness goes to the turn signal flasher, but unsure the function of the two orange wires in this harness and whether they are involved.  I have tried to study the wiring diagrams, but I am stumped.
Any thoughts
Thanks

[Bronzedodge]

Alright, Nacho would be the expert here, but we might need more information. The horn relay will not prevent the radio from working, or the car starting, unless it's shorting power constantly.  The radio and turn signals are in different circuits.  The orange wires are typically the interior instrument lighting circuit - only hot when the lights are no.  Usually not used unless your aftermarket radio has an input for it.

Why are you replacing relays repeatedly?

[Nacho-RT74]

Just read this last night but was in bed ( I'm in Spain so the hour difference didn't help LOL )... will post later after try to understand better the problem

[Nacho-RT74]

OK lets see. First the horn relay has nothing to do with ign system. The only relation with "ignition" is the ignition key in Buzzer, but is just a sensor/switch for the ignition key cylinder. Diagram attached about how is wired and sharing the same ground signal switch from driver side door for lights on warning buzzer

I'm actually wondering which relay are you playing with. The original one mounts on top of fuse box. It gets a violet wire on back ( batt source ) black wire to activate the key buzzer ( negative ), black wire coming from horn switch at steering wheel ( negative ), and green traced red wire to source the horns ( positive )

[Nacho-RT74]

About radio... Yes, the positive source comes from turning flasher plug, but thats just a splice from there to be fed from same ACC fuse on fusebox saving some wiring between fuse box and Radio. However has nothing to do with turning signals actually. ( aside just a volume decay on Radio when turning switch works LOL ) However the Radio should get a RED wire, not black, althought the hazzard flasher plug is still black, but becomes red from there to Radio as far I recall ?.

Black and green wires on Radio is the speakers output ( and violet if stereo )

As mentioned, orange wire network is the source from cluster lights dimmer controled. This orange wire comes from fusebox ( separated from the buss bars ) and is spreaded all around the dash wiring to feed everything what is lighted up the same as the cluster: Cigar ashtray light, Radio face, Shifter lettering, Cluster, Heater-AC control, any other accesories switch down the dash on driver side.

So, or you are playing with some other relay around and maybe added by a previous owner or wiring is completelly hacked up.

[b5blue]

Could it be seatbelt interlock? 

[Nacho-RT74]

interlock is 74 deal, not 73.

And still, horn relay has nothing to do with ign system

[b5blue]

Check column harness connector, the big red wire is prone to being toasted. Wiggling it while working on harness could be intermittent and confusing problems.   

[Bwword]

Thanks for all the good info:

I understand the radio wiring issue, but am still a little stressed about the ignition.

I started out by removing the instrument panel to replace a panel light and change the instrument voltage regulator in order to "fix" the fuel gauge. While the panel has been out,  I have manipulated the radio wiring. during this process the car would not start and the key in buzzer stopped working. The horn still functioned fine.
I did replace the relay that Nacho mentioned above - The car then started fine, but now, after further fiddling with the radio wiring, the car will not start - The key in buzzer is extremely quiet and when I turn the Key, the power indicated on the ammeter drops to 0.

Thoughts
other than stop fiddling with the now understood radio wiring?

thanks again everybody

[Nacho-RT74]

drops to 0 means drops to full discharge ?... 0 is center and thats the best ( and initial ) reading

[Bwword]

Sorry
I mean there is no power. 

[b5blue]

Wiggle the key lock and move the harness around, move the shifter around to check the NSS.

[Bwword]

Actually wiggling the key lock allowed the car to start.
I feel like a dummy.
Thanks to everyone for the advice

[b5blue]

We have all been there! 

[Bronzedodge]

Make sure your ammeter connections are tight, if you had the cluster out.  A well known trouble spot in the older ones.