Hi All,=

What is the procedure for bench testing horns out of the car?   It's a '72 240Z.  I bought 2 supposedly working, rebuilt horns from ebay and want to test them prior to installing.  I tested both horns individually by connecting their spade connectors to 12.7 volts and grounding the mounting brackets.   No sound on either.  The connections are all very clean (by me)  and I I measure 12.7 volts passing between the spade connectors and the grounds.   What am I missing?  Thanks! 

I used a clip lead and remote starter. https://www.amazon.com/INNOVA-3630-Remote-Starter-Switch/dp/B000EVU8MK

Clip one end of the clip lead to the negative of the battery and the other to the body of the horn.

Clip one end of the remote starter to the positive of the battery and the other end to the terminal on the horn. I suggest holding the horn so the positive terminal cannot touch the body of the car and short.

Press the button on the remote starter.

I’ve found pretty much the same issue with about a dozen non-working horns now, and it relates to corrosion in the power connection terminal where it passes through the body of the horn.

You can clean both sides of it thoroughly inside and out, even by sand blasting, and it will look like a million bucks but will not pass current. The corrosion between the touching mating surfaces of the metal bits that make up this insulated pass through connection are severe enough to insulate. I have had to grind the head off the rivet and separate and clean ALL the metal contact surfaces to get it to work again. 

The rest of the horn internal parts are rarely the issue.

36 minutes ago, zKars said:

I’ve found pretty much the same issue with about a dozen non-working horns now, and it relates to corrosion in the power connection terminal where it passes through the body of the horn.

You can clean both sides of it thoroughly inside and out, even by sand blasting, and it will look like a million bucks but will not pass current. The corrosion between the touching mating surfaces of the metal bits that make up this insulated pass through connection are severe enough to insulate. I have had to grind the head off the rivet and separate and clean ALL the metal contact surfaces to get it to work again. 

The rest of the horn internal parts are rarely the issue.

Yep, that's what I saw, too.

Thanks all.   I just bought denso.  horns and installed them.   Not OEM, but i now have a working horn which is awesome!.