My FJ62 horns were nearly silent at highway speed and it was really dangerous; there have been a few times where someone has not been able to hear me honking and I've had to take an evasive maneuver. Decided to knock out the Hella supertone horn install tonight. Here's what I used:
Given that mine was already relay-switched, I could have honestly just spliced in the new horns by cutting the old connector out and wiring the new horns directly to the old wires (+12V_always and GND_switched). However, these wires are tiny and each Hella horn consumes ~5.5A at 12V...so I figured I'd use the Toyota signals to switch a SPST relay that's directly connected to the battery with a larger gauge. I didn't need wires as large as 12 AWG, but it was just what was going to show up from amazon overnight & I wanted to do this ASAP for safety.
You'll know if your truck is not relay switched by using a multimeter to test each signal on the connector of the old horn once you remove it. Put GND on anything metal (bolt / battery -, etc), and + on a single pin. See what it says. Check the other. If one is +12V even when the horn is not pressed, that means it is relay-switched. If they are both reading 0V until the horn is pressed, and when the horn is pressed one reads +12V, then the current is passing through the steering wheel in some way. Either way, the directions below are the same.
It's midnight so excuse the Google slides schematic lol, but here is how I wired it up:
Summary:
Some pics, showing the old horn next to the new for size as well:
- Hella supertone horns - bought on amazon
- 4-pin waterproof relay with wire adapter (link)
- Braided cable sleeve to make the harness, though you should probably use something like this instead
- 12 AWG in-line fuse along with a fuse of your choice (I did 20A)
- Butt splice connector kit (used the blue & yellow)
- Specialized crimping tool for butt splice connectors
- Ring terminals to connect new harness(es) to battery (size for > 12A)
- 1/4" spade quick disconnect female connectors, sized to fit whatever wire gauge you use (I used 12 AWG)
- Dielectric grease
Given that mine was already relay-switched, I could have honestly just spliced in the new horns by cutting the old connector out and wiring the new horns directly to the old wires (+12V_always and GND_switched). However, these wires are tiny and each Hella horn consumes ~5.5A at 12V...so I figured I'd use the Toyota signals to switch a SPST relay that's directly connected to the battery with a larger gauge. I didn't need wires as large as 12 AWG, but it was just what was going to show up from amazon overnight & I wanted to do this ASAP for safety.
You'll know if your truck is not relay switched by using a multimeter to test each signal on the connector of the old horn once you remove it. Put GND on anything metal (bolt / battery -, etc), and + on a single pin. See what it says. Check the other. If one is +12V even when the horn is not pressed, that means it is relay-switched. If they are both reading 0V until the horn is pressed, and when the horn is pressed one reads +12V, then the current is passing through the steering wheel in some way. Either way, the directions below are the same.
It's midnight so excuse the Google slides schematic lol, but here is how I wired it up:
Summary:
- I did not use the driver's side original horn signals. Just electrical-taped off the connector and zip tied it to a nearby harness
- I cut out the connector on the passenger side, and used blue butt splice to connect +12V to coil+ and the floating switched GND to the coil- of the SPST relay
- I connected SPST relay COM to the battery: relay wire to yellow butt connector, and then other side is a new wire terminated by a ring terminal
- I connected SPST relay NO to a new harness I made, which provides +12V to both horns when NO is closed by the relay. The two horn (+) wires are joined together in a single yellow butt splice connector, which is then crimped to the NO output from the relay.
- Use the female spade connectors to connect your harnesses to the horns. Put on some dielectric grease to make sure these connections don't corrode & are worry free for many years!
- As part of the harness above ^ I also ran a GND between the two horns - this also meets at a yellow butt splice connector, then is crimped to a new wire that runs directly to the battery (-) and is terminated by a ring terminal
Some pics, showing the old horn next to the new for size as well:
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