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Everything You Ever Wanted to Know About 1969-1970 Mustang Horns
All About Horns, and the Oil Cooler Option
Editor’s note: Marcus Anghel owns and runs Anghel Restorations in Scottsdale, Arizona, and has been seen in Mustang Monthly a few times over the last year or so, providing readers with highly detailed restoration information. This month he brings us the inside scoop on ’69-’70 Mustang horns and mounting hardware.
All 1969 and 1970 Mustangs, Bosses, Shelbys, and Cougars used the same high and low pitch horns mounted to the radiator support. The horns were always installed in pairs and sounded together to produce a more perceptible sound rather than two horns of an identical frequency. The ’69- and ’70-style horn, including the mounting bracket assembly, was never actually serviced by Ford. Instead, Ford sold a universal horn assembly kit that included an adjustable bracket and could be used on all the different models of cars. The assembly line, correct-style original horns are shown here.
Taking it All Apart to See How it Works
This is what a horn looks like when it is completely opened up. The pieces consist of three diecast sections, a steel diaphragm, an electromagnet, contact points, gaskets, and rivets. When voltage is applied the electromagnet is activated, which oscillates the diaphragm. This opens the contact points, which in turn de-energizes the electromagnet, relaxing the diaphragm. This happens hundreds of times a second, which then blasts through the megaphone housing creating the sound.
All horns were originally dipped in paint (not sprayed) and although not easy to spot, can be seen in some of the runs that originals have.
All horns during this time period have date codes that were either stamped into the housing near the edge of the bellmouth, or on rare occasions were ink-stamped just inside the bellmouth.
For a standard horn installation (no oil cooler) the assembly manuals for 1969 and 1970 both show the bolt being installed from the back of the radiator support and the lock nut installed from the front, but this was not always what was done on the assembly line—it could have been installed either way. Notice that the bolts have serrated washers to help cut into the metal for better grounding of the horns.
Grounding and Paint
At some point in 1970 production, Ford added an extra grounding point to the wire harness in the horn area.
Oil Cooler Option
The radiator support would be modified at the factory to allow the horn to be relocated on these cars to make room for the oil cooler (if so equipped). It was available on certain Mustang, Cougar, and Shelby models with a 428 big-block, ’70 Boss 302s that were equipped with the oil cooler, all ‘69 Boss 302s, and all Boss 429s.
Horn Reinforcement Bracket
This bracket should have been placed behind the radiator support to strengthen the area where the horns were being mounted, however not every car had them installed from the factory. Three different styles are shown here starting with the first generation bracket used in 1969. Then, with changes in the radiator support and possible inference with the hood locks, the bracket was modified in 1970 by cutting the edge. Ford assembly manuals confirm this change.
Bill Upham, from Mansfield Mustang, makes an excellent reproduction of this bracket. He can be reached at (508) 339-5409 or at www.mansfieldmustang.com.
Horn Jumper Wire
Photo from Jim Woods
A special jumper wire was used to connect the two horns together from the same contact point of the main wiring harness. Two basic versions of this wire existed in which one was blue with a yellow stripe and the second was blue with the engineering number printed on the wire as C9DB-13A840-A. It is believed that a paper tag was only applied to the wire without the printing to identify it since the printed version already had the engineering number.
Horn Mounting With Oil Cooler, 1969 Vs. 1970
The mounting location of the horns was changed from 1969 to 1970 because of clearance issues. When moving the high-pitch horn to the passenger side, there is a tab that could rub against the hood, as shown here, causing damage to the hood and the horn. On some horns you can actually see this tab bent or worn down.
To overcome this clearance issue the position of the two horns was actually switched at some point into 1970 production. This eliminated the horn tab rubbing up against the hood. Interestingly, for the oil cooler option location only, the assembly manual shows the bolts being mounted from the front of the radiator support in 1969 (left), and then shows them mounted from the rear in 1970 (right).
For those who are interested in having original horns restored, one source is Gary at The Horn Works. Reach him at (608) 361-0095.