The Stovebolt Site Forums The Shop Area The Electrical Bay Vintage horn: wiring polarity discovery

So, I restored the vintage horn on my '52. Got it working great on the bench at 12v. Installed in truck and immediately burned up the spring in the contact at steering wheel. Replaced and happened again. But heavier spring in contact and added horn relay. Horn would work occasionally and then stop working. I could jump a spare 12v battery across terminals and get it working again for a few blasts.

Finally, I decided to change polarity of wires at horn. No more trouble and horn works perfectly all the time every time. Why, I have no idea. Just thought others might like to hear this in case they are having the same trouble...revers the polarity at the horn.

Well, no body jumpin' in here David, so I'll take a stab at it.
As far as I know there is nothing in a Klaxon horn that is
polarity sensitive. My guess is that when you disturbed the
contact by switching the wires, making a better path for the
current is what you are experiencing.
DG

pre-horn relay, one horn terminal is to power the other is to the horn button, which supplies the ground, correct connection [not "polarity" really] avoids current thru the column, reversing the connections causes the path in the column to carry full operating current, not a good thing

Bill

red58, what do you mean by pre-horn relay?
Carl

52Carl,

In the early days (not sure what year the relay set-up came out) the horn button wiring was big enough to carry all of the current to the horn, no relay was used.

Now the horn button (small wire) controls a relay that with a big wire that passes the full current to the horn.

Hope this helps...

Mike B

the years before GM wised up and added a relay to the horn circuit, about 54? then the horn only had 1 connection, power from the relay and the horn mount is its ground

Bill

It seems I was not clear. My '52 is a pre relay design. I added a relay. Before the relay, I was burning up the horn contact in short order. Actually, the spring inside the contact was getting hot and loosing its temper and thus no longer allowing strong contact at the contact ring. Never could get the horn to work with this setup.

So, I added a relay and the horn worked for a short period of time and then stopped working. The relay was still working as I could hear it clicking. To answer Denny's comment, the wiring at the horn was removed and reinstalled many times in an attempt to get the horn working. The horn was rebuilt by me and all hardware/connectors new and clean. So, not a connectivity/resistance issue. I could make the horn work by apply voltage directly from a small hobby 12v battery. Then the horn would work again for a few blasts and quit. Use the small battery to get the horn working again and repeat the process again....

Finally, I decided to reverse polarity at the horn (what the heck right?) Bingo, no more trouble. But why?

Got me stumped David. Shouldn't be polarity sensitive, and you've eliminated any chance of it being a poor connection issue.

DG

Maybe your original horn doesn't like the relay or there is something amiss with the relay. When they started using horn relays, they also started to use a different type of horn.
Carl

Carl, maybe. But, the horn never did work without the relay either. Worked better with the relay, and now perfect with relay and polarity at horn swapped. The engineer (by degree) in me wants to know why this made a difference. But, ultimately I am just glad I found a solution that is working.

Here is my best guess:

Fact 1: It worked better with the relay. The purpose of the relay is to handle the high current to the horn without the high voltage drop that would occur at the horn button contacts.

Fact 2: The horn worked well when connected directly to a 12 volt battery.

Evaluation: Both facts correlate reduced voltage across the horn to lack of function. The horn is in poor condition. Voltage drop in wiring or switch contacts causes it to quit functioning. It is operating very close to the transition from a non-working state to a working state. A very slight effect in the system may shift it from the working state to the non-working state.

Proposed cause: The armature has some residual magnetism. When current flows through the coil in one direction, the residual magnetism increases the attraction of the armature to the electrically magnetized core. The horn works normally.
When current flows through the coil in the other direction, the residual magnetism reduces the attraction of the armature to the electrically magnetized core. This reduced attraction causes the contacts in the horn to fail to open, which causes a high average current flow, which causes a high power dissipation in the horn button since the horn button switch has a high voltage drop, which causes the horn button spring to heat up and loose its temper, which causes a new horn button spring to be purchased and installed.

Dang, there's that new guy again! You go Sput! (As the kids say these days. I think they still say that, don't they?)

"Sput"

Here is another "fact". Polarity when connect directly to a 12v battery makes a difference as well...same symptom. That is what actually clued me into swapping the polarity to begin with. All wiring in the entire truck is new and I took care to ensure excellent contact points throughout. The horn has a dedicated ground.

The condition of the horn is definitely plausible and a likely contributor. Probably a little more fine tuning of the horn will make it work better. But now, it works flawlessly the way it is.

This is great . My problem is the same or close . I have a 12 volt system with a 6 volt horn and as soon as I drop the contact in the steering wheel it heats up and burns out. I don't have a relay installed . but have one ready to add if needed. I also have a manual to make sure the steering wheel assembly is correct . But the picture is not like mine at all. Is there a spring behind the steering wheel that sit's in the bearing cup ? And is there a spring that sit's under the contact plates ? Thanks