Horn Problem

[mamoose124]

I need a bit of advice on fixing my horn. First, the horn is no longer in the steering wheel. It is now a button under the dash. When I press the button, I can hear a weak sound coming from the horn on the driver's side (right side). There is juice getting to both terminal connections on both horns. However, they receive only 5 volts. The car has 12 volts. I'm thinking that 5 volts is not enough juice to activate the horns properly. So, what could be the problem?
Any suggestions would be helpful as I am electrically handicapped.

 

[bernd_st]

Hard to remote diagnose your voltage drop. Would recommend step by step approach, i.e. disconnect both jiuce lines and make jump wires from purple fuse Box connection (+12v) directly to the Horns. If grounding via the button works properly you should be able to hear Horns loud and clear. Reasons for the voltage Drop can be corroded connectors or internal Horn short...

 

[67Survivor]

Is the wiring original, or has somebody played with it at all? My thought is that when you see half the voltage you should see, then it may have been connected in series rather than in parralel. Series will put half the voltage at two devices, a third at three devices, a quarter voltage through four devices... Parralel will see full voltage at each device.

 

[RootesRacer]

With the ignition on and horn not pushed, both terminals of the horn should read battery voltage. The green wires terminal is battery voltage, the other will be taken to ground via the purple-black wire terminal from the horn switch.

When you push the horn button, the voltage at the purple-black terminal of the horn should go pretty close to 0v and on release go up to battery voltage.
Grounding the purple-black terminal right at the horn(s) should yield a strong horn sound for BOTH horns if the wiring is correct.

The horns current is taken in full through the purple-black wire so if its connection to the ground (via the switch) is weak then the voltage at the horns purple-black terminal will not go to 0v and the horn will be weak or not sound at all.

 

[P. Scofield]

There is a screw on the horn you can turn and adjust the sensitivity. Many of these old horns need a little tweaking on this screw.

 

[mamoose124]

There is a screw on the horn you can turn and adjust the sensitivity. Many of these old horns need a little tweaking on this screw.

P. Scofield, thanks for the note about the "secret" horn screws! Since it was the easiest thing to try (recall my electrical deficiency) I tweaked both "secret" horn screws first. Guys, you can imagine my surprise and delight as both horns loudly replied in their inimitable Alpine timbre! Problem solved.

Thanks to all for your suggestions.

 

[P. Scofield]

Great! Yes, there's a sweet spot on all these and seems to move, maybe humidity and other factors.

 

[mamoose124]

Great! Yes, there's a sweet spot on all these and seems to move, maybe humidity and other factors.

I guess I spoke too soon. After tweaking the horn screws the horns worked beautifully for a couple of days. Then, the car sat for a couple of days and when I tried the horns again, I got the original anemic low bleep out of each horn. Tweaking the screws on each horn did not work this time. So, I am back to square one. The horns are getting juice, and they do respond, but I can't get them to actually work. So, guys, any further suggestions would be appreciated.

 

[RootesRacer]

A voltmeter is probably in order.

Read the procedure I wrote up for you and use it.

If you have full voltage available after going through the procedure and your horn is sounding but weak, your internal points are probably corroded and may need to run for a while while adjusting for best tone (to burn the corrosion off the points).

 

[65beam]

horn

Smack it with a large hammer. It knocks all the rust and corrosion loose.

 

[tony perrett]

I seem to remember drilling out the rivets holding the horn together to enable the contacts to be properly cleaned. The fact that they worked for a few days would suggest a corrosion problem.

 

[Paul A]

I seem to remember drilling out the rivets holding the horn together to enable the contacts to be properly cleaned. The fact that they worked for a few days would suggest a corrosion problem.

Use a multi-meter and check the voltage at the horn with the engine running and the system charging. You should have in excess of 13.5 volts, perhaps as high as 14.4 volts. If you show appreciably less it would indicate high resistance in the wires - perhaps in a snap connector - not uncommon. The Lucas horns, when properly grounded and with full voltage, are excellent horns. With reduced voltage or internal corrosion they are quite anemic.

 

[Thor 1211]

Horns

I had the weak horn syndrome (this is a few years ago now) and as I recall the full horn power went through the button. Also, as I recall, it was a single wire no more than about 16 gauge and the operating stuff inside of the horn was a bunch of springs, rivets and screws with all sorts of places for current loss. It looked to me like a primitive system with lots of opportunity for failure. (If I am not recalling correctly I know someone will jump in and correct me.) I installed a DPST relay with a decent sized fused lead and the horns have worked fine ever since. Any voltage loss on the button side doesn't affect the horns.

 

[Tom H]

I agree. Adding a horn relay solved all my horn problems. The problem is the poor contact in the horn ring not able to handle the high current that the horns require.

Tom

 

[RHFG]

Same here, I had the same problem of getting the horns to work only to find a few days later they hardly produced anything audible. So I went with a relay mounted close to the fuses on the inner guard and bought some new horns which are much louder than the originals and quite a bit smaller. I have a Nardi steering wheel and the horn button contacts were arcing and burning with trying to supply full power to the old horns, very little power is required to trip the contacts in the relay.

 

[hartmandm]

Assuming you have verified the supply voltage to the horns, then verify the horns work as expected with a good ground. Disconnect the wire at the horn that becomes grounded by the horn ring circuit. Apply your own temporary ground to the horn connector. If the horn works fine, then you know your issue is with the horn ring grounding circuit and install a relay. If the horn doesn't work right with a temporary ground then you need to address that issue.

Mike

 

[mamoose124]

I assume when you mention the "horn ring circuit" you are referring to the steering wheel horn ring. As I indicated initially, my horn is no longer connected to the horn ring on the steering wheel. I have a horn button mounted under the dash. If you mean something else by the "horn ring circuit," please clarify.

 

[hartmandm]

I assume when you mention the "horn ring circuit" you are referring to the steering wheel horn ring. As I indicated initially, my horn is no longer connected to the horn ring on the steering wheel. I have a horn button mounted under the dash. If you mean something else by the "horn ring circuit," please clarify.

I'm saying swap out whatever circuit you are using to create the ground for the horns. Just connect a known good ground to the ground connector on the horn.

Mike

 

[mamoose124]

Use a multi-meter and check the voltage at the horn with the engine running and the system charging. You should have in excess of 13.5 volts, perhaps as high as 14.4 volts. If you show appreciably less it would indicate high resistance in the wires - perhaps in a snap connector - not uncommon. The Lucas horns, when properly grounded and with full voltage, are excellent horns. With reduced voltage or internal corrosion they are quite anemic.

Paul,

I connected my multimeter to the horn and the measured voltage getting to each horn is 14.3 volts. Still, I haven't figured out why the horns only offer a weak squeak. I'm uncertain which of the wires going to the two horn tabs on each horn is the ground wire. The horn on the driver's side (left) has two wires going to one tab and one wire going to the other tab. On the right horn, there is only one wire to each tab. As I previously indicated, my electrical knowledge is rudimentary at best. I really don't know which wire on each horn to disconnect in order to patch in my own ground. I don't want to start connecting wires willy-nilly and blow something important up. Any suggestions would be appreciated.

 

[RootesRacer]

Paul,

I connected my multimeter to the horn and the measured voltage getting to each horn is 14.3 volts. Still, I haven't figured out why the horns only offer a weak squeak. I'm uncertain which of the wires going to the two horn tabs on each horn is the ground wire. The horn on the driver's side (left) has two wires going to one tab and one wire going to the other tab. On the right horn, there is only one wire to each tab. As I previously indicated, my electrical knowledge is rudimentary at best. I really don't know which wire on each horn to disconnect in order to patch in my own ground. I don't want to start connecting wires willy-nilly and blow something important up. Any suggestions would be appreciated.

You want to measure both horn terminals to ground (independently) with the horn on (button pressed or switch closed). This will tell you not only if the wiring is weak (voltage drop) but on which side of the horn (power side or switch side) the voltage is dropping.
You have to do it with the horn blaring becuase if there is no load, there will be no voltage drop across the wiring.