Hi guys,
so if I'm ever going to get my car actually inspected I need to install horns! I have both a set from a 38 Buick (in unknown condition) and a generic pair manufactured for 6V negative ground. I also have a horn relay which I purchased from Bob's automobilia. So I believe in theory I have all the parts to at least pass inspection.
So I tried bench testing the horns using 6V at 2 amps as provided by my handy battery charger, and none of them make a real noise.. all of them seem to sort of make a vibration noise. Are they shot, or am I missing something?
Also, the relay I purchased from Bob's has (I think) three terminals... how do I determine which connection goes where etc?
Thanks in advance!!
-grant

The horns will not function with only 2 amps. You need to get a 6 volt battery and connnect it to the charger and test the horn circuit off the battery and charger. I will post the connection wiring to test the horns and relay later.
Joe, BCA 33493

Ah, got it... thanks for the info Joe, I will test them that way.

Connect a set of jumper wires from the negative side of the battery to the frame of each horn. This should be 10 gauge, but for testing 12 gauge will work. Connect a jumper from each screw terminal on the horns to the left terminal on the horn relay. Connect the positive side of the battery to the center terminal on the horn relay. Now connect a jumper wire to the remaining terminal on the horn relay. With the other end of this jumper, momentarily touch the negative terminal of the battery and the horns should blow.
Good luck.
Joe, BCA 33493

Joe, I don't recall whether my '41 has a relay for the horns, but I don't think so. If it did, where would it have been located? I took my horns apart to powdercoat them and have some concerns that they won't work when I put them back together and would also like to test them like you describe. Any ideas?

Thanks.

In most early post-war Buicks they mounted the horn relay on the firewall, passenger side, since the horns were mounted on the firewall. I believe this is also true for the early 40's models as well. Later models in the early 50's moved the horns in front of the radiator and so on these the horn relay is on the side of the radiator frame. Since these horns draw a good deal of current, they are generally fed with 10 gauge wire and Buick good engineering practice was to keep the wire runs to the horns from the horn relay as short as possible. There are numerous 6 volt horn relays on eBay.
It doesn't seem possible that the horn button, which is a low current grounding device, could ever complete the circuit for the horns given the high current draw, hence the need for a relay.
Joe, BCA 33493

That make sense, Joe. I'll have a look through my boxes of parts and see if I can find it. Would it have been part of the wiring harness or a stand-alone thing?

Generally they were stand-alone. Small black cover, mounting tab with 2-3 holes, three terminals to connnect to wiring harness. Go on eBay and search for "horn relay" under eBay Motors and you will see pictures of them for sale.
Joe, BCA 33493

Joe,
thanks so much for the info... I'm about to head out to my garage (rented space about 20 minutes drive away) for a day of work and will test the horns, will let you all know if they pass or fail!

Matt - my horn relay in the '38 is mounted in the engine compartment on the firewall pretty much directly over the steering column, to the left of the voltage regulator as viewed from the front of the car.

Hey guys,

so here is what I have found with the horn setup:

The horns themselves work! However, I can't seem to get the relay working. If I jumper directly from the hot wire to the horn wire, the horns blow. If my understanding of the relay is correct, jumpering from the other input of the relay (not horn wire, not hot wire) to ground should close the circuit between horn and hot within the relay and cause the horn to blow as well, correct? That is not happening.

Is my understanding of the relay flawed, is my relay defective, or ...?

Thanks again for the help guys!

Make sure you run a jumper from the horn relay mounting bracket to negative terminal on the battery. When mounted in the car, the relay was grounded (negative side of the battery) via the mounting screws to the firewall.
Joe, BCA 33493

Ah, good point... I'll make sure the relay's mounting tabs have a good ground and test again.