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240 Adding Cadillac horns

mblue240

Well-known member
Joined
May 22, 2007
Location
Portland, Oregon
I had the bright idea to add Cadillac horns to my 240, but now the wiring has me stumped. The Cadillacs only have one horn, so I bought one from two cars. They seem simple enough with a power and ground wire. I hooked them up to the 240 wires though and they honk constant when the ignition is on. I went down to one horn to try and trouble shoot it. When I swapped what I thought was power and ground I blew the fuse when I turned the ignition on. Any ideas?

horns by M. Blue 240, on Flickr
 
Cadillac horns to my 240.....

Volvo's horns do not use vehicle's ground....many GM horns do.

Volvo's horns have two terminals on them...positive juice is running to one terminal once ignition is turned on, or in ACC position....the other terminal connects to a grounding relay.

>honk constant

Yes, this suggests horn is grounded to vehicle....do the horns have two terminals on them?

Here's a diagram of a 1993 Cadillac Fleetwood...from it, it suggests horns are grounded to vehicle where attached.
 
I added a HF ooga horn to the v90 by splice the existing wires. Works great but our wiring is most likely different. Sorry to side track
 
Yes, this suggests horn is grounded to vehicle....do the horns have two terminals on them?

Yes, one green wire and one black. I bench tested it on a spare car battery. Black wire to the negative, green wire to the positive, and horn sitting on the wood bench. It worked just fine, and dang near hurt my ears.
 
I added cadillac horns, just use a simple Bosch type relay to swap polarity.

Google and learn about wiring up a simple relay, worth learning.

there's a good youtube vid about refurbing these old horns using silicone and replacing the rivets with threaded fasteners.
https://www.youtube.com/watch?v=L1kMJIKSEQc

I have the ultimate setup, 4 nautilus type of different notes, and the rare trumpet 5th horn.
you are going to want at least two of different notes, they are marked on the plastic shell, a little googling will lead you down a cool rabbit hole.
 
Just adding a relay to the stock 240 setup adds a considerable amount of volume. Not as loud as the caddy horns but totally loud and also do the job well. Another nice update is if you have a late model 240 with only one horn. Back date your car to a set of two horns like the earlier cars have. That and a relay make it very loud.

Yes that is correct. A volvo 240 doesn't use horn relays. Add a relay to your horns, you'll like it.
 
That makes more sense then the way you had them mounted before, in front of the radiator, blocking off a lot of airflow.
 
The older Cadillac horns are 4 horns (4 notes). Not sure how they compare to two horns, but I'm guessing pretty damned loud. It's on my list to do someday.

There's an install page here that explains things well: http://www.local1259iaff.org/cadillac4notehorns.html
Dave B

My wife did that on her 4Runner. Took off the little 'meep meep' palm buzzer stock horns, and added the full 4 horn set from a late model big-body Caddy. The big Buicks will also have the 4 horn sets, Oldslowmobiles and Chevrolets siblings only had 2.

It's a full orchestral range now. Very 'full' sounding.
 
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Every time I see this thread I think horns on a Cadillac.

long+horns.jpg
 
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