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Air horn installation...

Darrell Lee (

SE-R engine compartments are crammed full, so you're probably wondering _where_ you're going to find space to put your air horn. I'll tell you where I found mine, but good luck.

First, count up your nuts and bolts. If your horn doesn't have enough mounting bolts for the compressor and its two or three horns, buy them ahead of time. I also had a bracket (about 6" long) with a slot in it for variable mounting of the air horns (from a previous installation). It was handy.

Next, you need a soldering iron and 60/40 resin core solder and about 3' of electrical wire to extend the original horn wire. Get some black electrician's tape (or shrink-fit plastic insulator) to keep the bare wiring from shorting.

Get a blade connector for the compressor ground wire (find a dangling one off your car or off a junker). If you're a neatnik, buy a spade connector for the other end of your ground wire. Make a ground wire about 8" long with blade connector at one end (spade at the other is optional).

Buy a box of 15 amp fuses, too. 200SX SE-Rs use mini blade fuses. Classics may use standard blade fuses (I don't know).

Step 1. Mount your air compressor. On my 200SX SE-R, there was a lot of space on the left fender. I drilled a hole through the reinforcement groove for mounting. (When you open your hood, this is the innermost flat area of the fender). Even though the only bolt I had handy was about 1-1/2" long, and it sticks up through the groove, there's no interference with the hood. Drill the hole large enough to get your air compressor mounting stud/bolt through it. Put the bare or spade end of your ground wire around the bold and snug down the nut/locknut/washer-nut to hold the compressor.

Step 2. Extend your original horn's hot wire to the compressor. This requires some soldering skills, although you can crimp the wires with solderless connectors from Ratshack if you're electrically-challenged. I recommend solder, as you'll be pushing 15 amps through the circuit. Insulate your bare solder connections with electricians tape or shrink-fit insulation. Plug the hot and ground wires into your compressor.

Step 3. Mount the air horns. You want them outside the engine compartment, or the sound gets blocked by radiator, block, fenders, etc. I removed the OEM horn and bolted my slotted bracket there. The other end of the bracket holds two air trumpets pointed downwards. I removed a bolt from the hood release lever mount and put my third air trumpet there.

Step 4. Connect the air tubing from the compressor to the trumpets.

Step 5. Replace the stock 10 amp horn fuse with your 15 amp fuse. I've been told the relay is rated at 15 amps and your compressor is going to draw >10 amps, so put a 15 amp fuse in. On the 200SX SE-R, the fuse I'm talking about is in the fuse box in the engine compartment aft and inwards from the battery.

Step 6. Blow your new horn. If no noise comes out, you probably reversed your hot/ground wires and blew your fuse. Reverse the ground/hot wires and your horn fuse (you did buy a box of 5-15 amp fuses, right?) and try again.

Paul R. Detjens (

Comments to and Excerpts from Darrell's instructions:

I would strongly recommend using the relay that came with the horns and using the existing horn circuit only as the trigger to the relay. This allows the compressor to get the current it needs (= louder horns) and avoids the problem some others have had with blown fuses from running too many amps through the original horn circuit. (You don't want to find out you have no horn when some idiot is coming right at you! ;-)

I would also avoid the solder because the vibrations of your car will shorten the life of this connection. The amperage shouldn't be an issue; the spade connections are good enough for the rest of the circuits on the car.

The new circuit for the horn (per the Hella instructions) couldn't be simpler: 12V from battery to relay, then to horn, then back to ground (I used neg. terminal of battery -- see below). Another lead from the relay goes to the same ground. I used 12 ga wire with spade connectors for the main circuit, 14 ga for the trigger from the original horn, again with spade connectors (avail. at any auto parts store).

Drilling a hole through your fender and creating a decent ground there encourages rust. A simpler way is to use existing mounting holes, and run the ground back to the negative terminal of the battery or other established ground location. I was able to replace two of the plastic "snap-in" connectors on the fender splash shield with real bolts and nuts, and used these to mount the horns and compressor. Another very critical point to make is that the compressor needs to be mounted vertically or the motor will prematurely burn out (as experienced by Larry Weeks and recently by Pat Tilli).

I used a slotted bracket from an old light fixture. Bent the wings around, and mounted the horns on the ends. Looks ok, works great. Can only see it from under the car. I'll probably paint it to match one of these days.

I'd be concerned about spool up delay with this distance between compressor and horns. I mounted the compressor about 8-inches from the horns and have *no* noticeable spool up delay. My horns are low, and shoot to the side below the front splash shield. There really wasn't room behind the nose of the NX for an clean mounting arrangement (although Larry Weeks did it there, and is now thinking of moving them). The sound is plenty loud and is not muffled by the radiator or other engine components. I tried different locations before securing the horns in order to see if they would be muffled; I could not tell any difference in volume between the various locations I tried (then again, I was probably mostly deaf after a couple of toots ;-).

Some more data:

I purchased my Hella double air horns from Imparts: Part# 26023, $25.00 + $3.50 S/H. 1-800-325-9043. The package came complete with a relay, brackets and hose. I supplied the wire, fuse, spade connectors, and the additional bracket.

I have a problem with blowing the 10A fuse in the engine compartment every time I use the horn when I'm driving. Apparently, the horn draws enough juice to fry the fuse.

Rob Microys (

Been there, done that. I have the Hella triple air horns (nice aren't they?), I had the same problem about blowing the original fuse. The air compressor for the horns pulls over 10A, that's why you are blowing fuses, plain and simple. I stuck a 15A fuse in there and haven't had a problem since. It should work okay, because I check the factory horn relay and it is rated to 15A, and I don't think that you are going to have a problem with the wiring. Just stick the 15A fuse in and give the horn a good 10 sec. blast and if you don't blow the fuse, then you'll be just fine. If your compressor pulls more than 15A, then you might look at installing a 30A relay and bigger wiring.

Do we have a horn relay already in the car?

Gary W. Mahan (gwm@venus)

You could use the existing relay but then you would have to go into the wiring harness and splice in your new larger wire (not recommended).

I bought a separate relay and a few spools of 12 gauge wire (and a fuse of course) and ran the wire right to the battery. The switch lead was connected to the old horn wiring positive lead.

Because of how the relay I bought worked and many other factors, I had to remove my original horn relay and run some jumpers where the old bumpers used to be. I think the old horns always had the positive available but the horn relay switched ground. My newer relay was made to switch power (or was the other way around?????).

You should be able to find a generic horn relay for ~$5.

I've heard of people installing airhorns in the SE-Rs. Is it worth it? What's it like? How long is the spool up delay? Does keeping the hose short help? How loud are they really? Any installation tips?

David Schmidt (

Worth it? YES! I think they're a deal for $25.00. And loud, O MY GOSH THEY'RE LOUD!!! I have them on my old 200SX and my SER (horns face forward behind the grill on the 200SX. On the SE-R, they are between the battery and the left compartment on top of some relays).

In both cars, the compressor is run directly off the battery + terminal through a relay that is switched on and off by the stock horn. I kept the stock horn attached and working for redundancy (I've had compressors go bad from water damage before).

Out on the road, the horns don't sound too loud from the drivers seat, BUT. . . .point your car at a building, or better yet while you're in an underpass or under a freeway and hit the horn and you're deafened!. Goes to show how directional the volume is.

When you install, keep the air lines as short as possible. The spool up time is very short though. The compressor does pull a lot of current, be sure to use the relay that comes with it.

Pat Tilli (

I recently installed a couple of Hella Airs (part#85105). I had them installed behind the front bumper area between the headlights. I preferred to have them install upside down as they promised, so as to have any water drain out, but they installed them horizontally }---|---{. Also needed a relay and a 30A fuse. (20 & 25 Amps kept blowing!)

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