The f********** pos alarm went off again tonight while washing the truck. Grrrrr, I hate it when other people do that and hate it even more when it happens to me, I may or may not be an assortment of things, but hypocrite is not one of them. So, was the last time one of those things actually scared off a thief, in the Reagan administration or Carters? Designed I guess to appeal to the people who go Ooh when told it's got an alarm and Oh Yeah when told told it involves a horn. You know, the people who were the first in their family to graduate... from Elementary School. Designed, by I have to assume, either the developmentally disabled or the criminally insane.

So, I see a fuse marked anti horn. Is that the alarm system fuse? Is there an anti horn along with a posi horn? Was alarm horn not used because of the expense of an additional letter? Is the alarm a seperate module that can be unplugged or bypassed or will the truck not start at all? I don't think the whole truck runs off a computer, but I'm not certain. Can I yank it out, lay it across my anvil and have at it with a 3 pound hand sledge or should I start looking for a carb retrofit kit if I do? I've seen references to 3 horns at times, suggesting one is for alarm only, but only see 2 myself, although it's possible I've missed one. Would a manual horn circuit be the easiest way? I can do that. Easy.

The vaunted FSM does have a section on it, but it doesn't appear particularly useful. It focuses on a lack of activation, not false activation. Not a word on false positives.

So, how can I kill this thing, with fire, programming, pulling a fuse or brute force? My views run towards non violence, but there are cases where rendering a module into dust with a sledgehammer can be justified.

Sometimes our days are too frustrating as of late and these kinds of annoying car issues, especially noisy ones, just seem to yank on our last raw nerve. Put away the hammer or other implements of destruction though. You can fix this but it will take, dare I say, patience. Pulling the 7.5A anti-theft horn fuse from the box under the hood might shut it up but your headlights might still flash as they do when the alarm is triggered. Pulling it might not do anything given how Nissan and Infiniti have made so many electrical changes and not updated their published schematics and services manuals. There used to be a high-tone and a low-tone horn mounted in front of the radiator and an anti-theft horn mounted behind the battery and then there was just a low-tone horn in front of the radiator and the high-tone horn behind the battery but it was still identified in documents as the anti-theft horn.

The problem you are having might simply be a door, hood, or hatch switch getting wet and closing the switch circuit or shorting it to ground when the alarm system is active. These switches are simple Open-Closed contact types. The switch contacts are open when the doors are shut and closed when the doors are opened. The four door and the hood switches are the most obvious and easiest ones to visually inspect. In the door jams, there is a rubber boot covering the switches, protecting the switches from water getting into the switches. These boots deteriorate and crack over time which could allow for water to get into the switch. The hood switch, located on the driver side, top, front corner of the engine bay, near the radiator, is much larger than the ones in the door jams but the same conditions apply. Look for cracks and leaks in the boots. The rear hatch door and glass hatch switches, located at the latch mechanisms, have a different type of simple switch with two contacts held apart by a spring when the hatches are closed. These tiny springs and the contacts are totally exposed. If water gets inside the hatch door and drips onto the switches, the circuit can close or short to ground and set off the alarm. A buildup of dirt and grime on these exposed switches makes them more susceptible to a ground short than a closed circuit occurrence if water gets on them. Clean them with an electrical spray cleaner and look for areas where water may be leaking into the hatch.

I hope you find the problem not to be as alarming as it sounds. Good luck.

Thanks for the calm and detailed response. While normally pretty easy going myself, car alarms and horns are a hot button for me and yes I was livid. And the alarm system seems to be a weak link.

Even if the headlights flash, not having the horn do it's thing would be a huge improvement alone. I suspect the hatch might be cranky, it was hit in the rear prior to my ownership and while it's straight, it's not in perfect alignment with the rest of the body. Additionally the interior light can sometimes go on and off with no apparent reason while driving. This has happened before, but I had been on the rear bumper and just stepped off. This time I was washing the drivers door window with a car wash sponge. I might have been on and off the running board but I don't think so. I didn't dig in far enough last night, but it appears it all goes thru the "Smart Entrance control unit"? And where is that control unit? I'm seeing some possibilities there to interrupt the circuit to prevent the horn from going off. While a nice one, at this point in it's age/value I think the smart key is plenty of theft deterrence even if the alarm ever did any good, which I doubt it did.

Somewhat calmer. I wasn't so much interested in getting the alarm to function as designed, more wanting it not to go off again when it shouldn't. I did eventually find more detailed info, at least in terms of the wiring than previously. Being an electrician/electronics tech I was puzzled at first by the nomenclature. Closed, means the circuit is closed, or connected. Open the opposite, but the schematic shows closed as open and visa versa. It seems to refer to the door, not the circuit. Since the hatch was suspect, I disconnected the plug going to it, to I assume take it out the the equation, I can live with the light not coming on from the hatch. Next looking at the horns, the anti horn fuse is one of the horns, the tenor I think, but I'm not positive. The horn fuse is for the baritone horn. Then since it shows a signal coming from the Dumb, er Smart Entrance control unit going to the horn relay, #42, which matched a color going to the horn relay. I tried to extract the pin from the connector once I figured out what was where since the control unit is upside down from what the schematic shows. No luck on extraction and I've had pretty good luck in the past improvising tools for pin extraction. So I pulled it out of the harness a bit and went for the wire cutters. Long enough to reconnect if for some reason it should be needed, but currently insulated with heat shrink tubing.

Hopefully this will prevent future false activation of that bleeping alarm horn. Overall, not as bad as I feared. Still pi****** I should have to dig in there, but not that bad. Next time it would be a snap.