How to test a car Horn ? 12 v , 3 A

How to test a car Horn ? 12 v , 3 A

measured resistance is almost 3.6 ohms ......

but its not working

thanks

Most car horns have a metallic diaphram with a set of points behind them connected in series to the driving solenoid. So the contacts are made, current flows the diaphram deflects opening the points the current stops the diaphram returns to its starting position. So in your case it looks as though the contacts have welded them selves closed. If this is so when you connect the voltage the diaphram should go click and move inwards and not do anything else. I have attempted to mend a horn by drilling the rivets out but it is very difficults to re-assemble, due to the fact that one has to "hook" the contact on to the diaphram which is closing the opening.
Frank

There is s self make/break switch type device. It has a magnet coil inside connected through a switch which breaks when the Horn Switch is pressed and the magnet is deactivated causing the the circuit to complete again magnetising and breaking again and so on .............
With the passage of time the contact of the switch inside get carbonized or burns due to sparking. Here is the outer image of the Horn, it has got a SCREW with a locking Nut.

Release the nut and adjust where you can listen the Horn working (must be connected to Battery). Tight the nut back and enjoy.

Raza said:

There is s self make/break switch type device. It has a magnet coil inside connected through a switch which breaks when the Horn Switch is pressed and the magnet is deactivated causing the the circuit to complete again magnetising and breaking again and so on .............
With the passage of time the contact of the switch inside get carbonized or burns due to sparking. Here is the outer image of the Horn, it has got a SCREW with a locking Nut.
View attachment 62715
Release the nut and adjust where you can listen the Horn working (must be connected to Battery). Tight the nut back and enjoy.

Click to expand...

so, what to do with the carbonized or burnt contact ?

I tried to clean it with sandpaper but neither my hand nor my fingers got there ........

thanks btw

The horn is sealed, you can not access the contact until you open the seal. And once the seal is open, you will be unable to seal it back, as the seal done on the machine and without cutting it you can not open it. If the contact is burnt you can not repair it. Or you have to fix it like this:

Raza said:

The horn is sealed, you can not access the contact until you open the seal. And once the seal is open, you will be unable to seal it back, as the seal done on the machine and without cutting it you can not open it. If the contact is burnt you can not repair it. Or you have to fix it like this:
View attachment 62737

Click to expand...

Ok, thanks a lot ..... so , have to purchase down the new horn .....