Electropneumatic Fun

Dual Air Horns
Originally uploaded by The Put-Man.

As many of you know, I own a 1974 Fiat Spider.

The car is currently marooned, not running in my garage due to many back-ordered bits and pieces. Last weekend I went ahead with doing what work I could, while I wait for other parts to arrive from around the country.

One item I decided to work on was the car's horn.

Back in the day, Fiat called the assembly an "Electro-pneumatic Horn", which the rest of us would call an "Air Horn". It consists of an air compressor, a few hoses, and two air-horn trumpets. When working properly, it provides a crisp, bright, immediate and very distinctive bark of the horns. Perfect for scattering crowds of espresso drinking loiterers in the town piazza.

Mine horn, however, sounded more like an elderly wounded goose.

As it turns out, only one of my dual horns was making noise. I assumed it was because the air compressor wasn't pushing out enough air, so I pulled it apart. I cleaned it, lightly lubed it, and put it all back together, fully expecting the reward of a bright, loud horn - justification of a job well done.

Ready to test.

No difference.

Bad words muttered under my breath.

Well, the hoses looked pretty old. So, I pulled them off. Broke the original plastic "Y" connector. Got a new "T" connector and new hoses from Home Depot. An hour later, hoses cut to fit, I got them installed.

Ready to test...

No difference.

One bad word, said fairly loudly.

Unbolted both horns from the grill area. After scraping a knuckle, kicking the car, and then cursing; I pulled the horns out, and looked down the trumpets. One had what appeared to be a spider's nest blocking it. After screaming and throwing it out in the yard, I found my lighter fluid, and approached it with caution. One short horn-barbeque later, I felt sure I'd killed any stray arachnids, and picked it up to examine my progress. After screaming and throwing it into the neighbor's yard, I got heavy gloves and picked up the still-red-hot horn. I melted a new hose connecting it.

Ready to test...

No difference.

String of bad words shouted.

Well, now it was time to get serious. I'd noticed that the base of the trumpet where it attaches to the horn housing had what appeared to be a lock-nut...it seemed that the trumpet assembly screwed into the base. AHA! Something ELSE for me to take apart! Easier said than done, I ended up bolting the assembly to my work bench so that I could leverage my crescent wrench enough to break the nut loose. Unscrewed the trumpet, and found...absolutely nothing of interest inside the base housing.

Screwed that sucker all the way back in. Then with a stroke of inspiration, I put the compressor hose nipple in my mouth and took a deep breath.

Ready to test...

No difference.

Loud, frustrated, guttural roar with no discernable words.

It occurred to me briefly to wonder WHY there was a locking nut. Shouldn't you just screw the trumpet ALL the way into the base?

I didn't know.

With fresh inspiration coursing through my veins, I UN-screwed the trumpet two full turns. Nipple in mouth, I blew HARDER.

(Turns out, by the way, when the compressor nipple is in one's mouth - the trumpet is in one's ear. That's a helpful hint for the next time you're working on an Italian air horn.)

Fucker worked great.

Now I just can't hear anything in my left ear...

New trick is now getting BOTH horns tweaked (by adjusting how far they are screwed into the horn base) so that they EACH get the SAME amount of air-throughput. How to do this without constantly hitting the horn button, I'm not sure.

I quit that night, because at 10pm, my neighbors seemed to be getting twitchy.

...and I still can't hear in my left ear...