Re: 1937 120C horns
Posted by HH56 On 2023/10/23 15:11:02
One other possibility might be the contacts arced or burned. Best case scenario is they burned and oxidized and can no longer conduct or possibly the gap changed enough the contacts lost the ability to close. The worst case option is they arced and welded closed and the electromagnet coil then burned open.
To make sound, the contacts must be closed when power is first applied. The diaphragm will move and immediately open the contacts and the cycle rapidly repeats as long as there is voltage present. The gap determines frequency along with volume and if the contacts cannot provide power to the electromagnet the horn will be silent.
I don't know which model horn is in your car but they all work the same way, just have different layouts of contacts and adjustment methods. You should be able to identify and check the contacts by following what part of the unit is connected to the wire terminal. Here is a bit from the prewar service manual showing a typical horn and adjustments.
Attach file:
horn.jpg (294.83 KB)
To make sound, the contacts must be closed when power is first applied. The diaphragm will move and immediately open the contacts and the cycle rapidly repeats as long as there is voltage present. The gap determines frequency along with volume and if the contacts cannot provide power to the electromagnet the horn will be silent.
I don't know which model horn is in your car but they all work the same way, just have different layouts of contacts and adjustment methods. You should be able to identify and check the contacts by following what part of the unit is connected to the wire terminal. Here is a bit from the prewar service manual showing a typical horn and adjustments.
Attach file:
horn.jpg (294.83 KB)
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