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Car Alarm Install: 85 Chevy Suburban

21 October 2005 No Comment

Having had a car stolen from us earlier, one of the first things we did when we picked up the old ’85 Suburban pimpwagon was pick up a cheap alarm system just to add as a deterrant. If nothing else, I kinda wanted the remote keyless entry stuff just as a toy. Our car had factory electric locks, so that made things a good bit easier. So I guess you could say this is just a “How I installed an alarm into my 1985 Silverado Suburban” article.

Selecting an Alarm System.

Ages ago when I was first taught how to install car alarms, the addage passed around was that car arlam installations are “10% product quality, 90% installation quality”. That is to say that a 2005 model Viper car alarm, if installed poorly, will be less secure than a $30 import that’s installed well. When paying for a car alarm, you’re paying for features extraneous to the actual protection of your car – so it’s basically just whether or not you feel like paying a few hundred bucks more for things like remote engine start and whatnot.

Of course, I would love to have these extra features to play around with – but I lacked the budget at the moment. So I went and picked up a cheap-ass alarm system manufactured by Phoenix Digital. It’s not the greatest thing in the world, but for around $40 you really can’t complain. It has an optional “trunk popper”, which is really just a simple way of saying one auxillary output, which I’ll be using for my own nefarious purposes.

It also comes with two remotes, a cheap siren, a dual stage shock sensor and all the bullshit you need to hook it up. The whole thing comes in a few plastic packages that overall give you the feeling it was made in a sweatshop. But it will suffice. It also comes with a warning sticker, which I consider to be detrimental to the effectiveness of an alarm system.

Do we warn?

I said above that I think the warning stickers are a bad idea. I also didn’t hook up the supplied flashing LED. A lot of people consider an alarm to be a deterrant, and a flashing light will convince a would-be thief to move on to the next vehicle. The problem is, a determined thief will be given a “heads up” that the vehicle has an alarm installed, and take steps to silence it as quickly and quietly as possible. With two people and your average “under hood” screamer mounting, in less than 10 seconds an average alarm can be silenced.

If they’re prepared for it, that is. Giving them warning, and having a good, well calibrated shock sensor will mean that their first indication of an alarm being audible to the rest of the world, and all but the most determined thief will flee after setting off an alarm unexpectedly.

There are a few drawbacks to this approach however. First of all, it’s not guaranteed. They might either not be too fussed over setting off an alarm, or they might guess there’s one installed anyway (and thus be prepared for it). Second of all, depending on the standard vector of entry for your given vehicle, you might want to warn them after all. You see, if it’s just joyriding kids that don’t really know what they’re doing, a blinking LED will generally be enough to stop them and make ’em move on to another vehicle.

If there’s no blinking light, your alarm’s first attempt to warn them might be a hammer going through your driver’s side window. With my particular truck, there are small triangle window/vent deals in the corner in front of a square door window – this is generally the most popular area for entering my vehicle, as the electric door unlock button is mere inches from it.

This means that someone breaking into my truck will most likely take this quiet, minimal damage approach, as opposed to sending a claw hammer through my window. This makes not warning them an excellent idea, and that’s why I chose to go this route.

Planning the installation.

The first thing you need to figure out is where you’re going to mount the control unit and the siren. The siren should be under the hood, but in a location that’s very difficult to get to. My general rule of thumb is that if you don’t grunt and swear for at least 10 minutes putting it in, it’s not in the prime location. Facing it downwards is a good idea for two reasons, apparently I’m told it keeps the rain out (should any get around the hood of your car), and second it has the effect of “bouncing” the noise off the ground, which makes it less muffled than bouncing it off a hood (which normally has some kind of sound deadening).

For my particular installation, I chose to mount the control module behind the instrument panel, under the very top of the dash. The reason for this choice is that removal of the dash isn’t a quick job – it took me a good 20 minutes to half hour, with the right tools and daylight.

Let’s begin!

The first thing you’ll want to do is remove the negative lead from your battery. Regardless of the cost of your alarm, you can bet your ass if you spark something it will cook it just to prove murphy’s law. So take the negative lead off the battery just to be sure.

Find a suitable place to tap power from, I already have a fused lead coming in for the stereo receiver, so I used that. The Phoenix Digital alarm I bought came with a small fuse on the power cable, but it’s next to useless. Ideally speaking, you want the fuse as close to the battery as possible, having it right next to the alarm module is pretty silly. I left it in just because, but hooked the power wire up to my existing wire. It turned out the ground I chose was very poor, as explained later, but I soon selected a better one by using the nice grounding block that’s on the driver’s side wall behind the instrument panel.

Next up came the wiring for the door triggers. The simplest way to deal with this is just to tap into the negative-switched output from the door switches that heads to the courtesy lamps. Conveniently, in my truck there’s one located under the dash right in the center (right by the courtesy lamp under the dash), and splicing into the wire is simple without taking a huge wire run anywhere.

In my case I hooked the negative tripped wire to the courtesy lamp sire, and I’m good to go. In fact, my truck had a previous alarm on it, and I jacked that wire to save myself even more work.

A cheap alarm and poor ground == weird shit.

As stated earlier, I’d initially chosen a pretty shitty ground. So shitty in fact, it didn’t do anything. Because I had a cheaper alarm system (more spendy ones might do it too) it chose to earth through the siren, which meant the siren stayed on constantly (although quietly) and nothing really worked right. I eventually figured out the problem, but it’s a gotcha nonetheless.

So make a mental note, that if the siren stays on constantly, check your ground!

Wiring the rest of it up

You’ll find that most alarm systems you will buy ought to come with a decent length loom enabling you to mount the alarm system just about anywhere. Follow your alarm system’s instructions, doing one wire at a time, and find the best route to hook it up with. I whole heartedly recommend sliding each wire down inside the harness cover closest to it, even if it takes a few inches more wire. I also definitely recommend soldering each connection and taping it with good quality electrical tape.

By now, I had the power (+/-), door alarm trigger, and the siren hooked up. The alarm module was mounted against the firewall (though in such a place where the screws didn’t actually penetrate the firewall), and I decided it was time to hook up the shock sensor.

Setting up the remotes

Now I personally like to leave my reset switch off – I trust the remotes to operate, you can tell when the batteries are going low, and typically I’m with my wife who almost always has her remote too. It’s entirely up to you. If you’re going to install it permanently, now would be a good time – make sure you choose somewhere that’s very tough to reach even if you know where it is. Remember, a would-be thief probably knows more tricks than you – so don’t go thinking you can fool them.

If you’re like me, and game enough to leave the reset switch off, then just go ahead and hook it up temporarily for now anyway. At least with my alarm, you need to use the reset switch in order to program the alarm system. Hold the button in, while having a friend or neighbour hook up the battery again (doesn’t need to be tight, just to make contact – you’re not going to start the motor). My alarm beeps once, then you press the arm button on each remote as you go to program it. Let the 30 second limit expire after the last remote, and the alarm should arm/disarm as it’s supposed to.

The reason I brought this up now, is because in most cases you need power to be able to properly set up the shock sensor.

The Shock Sensor

I don’t care what anyone else says about shock sensors, in my opinion they work best when anchored securely to the frame of the vehicle. People are always concerned about things like Harley Davidsons and passing band-pass subwoofer boxes setting their alarm off. Sure, you can sit them on carpet, and then about the only thing that will set them off regularly is a Harley Davidson. I screwed mine to the side wall of the dash, and ran the cable to the alarm module.

On my sensor, which is a dual stage, there are two calibration pots (potentiometers, think “volume control”). There are also two LEDs, an amber one and a red one. One pot, and the amber LED are for “Stage 1” – which is generally used for a warning. “Stage 2” has a red LED and is the real deal, when the entire alarm goes off. I’m sure you can think up a variety of ways to test the sensor while calibrating it, but I like to set mine so knocking on the hood sets off stage 1 and banging on the door sets off stage 2. You don’t actually have to set off the alarm, just power the vehicle up (by hooking the negative strap up for a while) and watch the LEDs while someone bangs on various areas – tweaking the pots as necessary.

With this setup, a passing HD motorcycle at idle will not bother it, but one passing revved up will typically trip stage 1 – often stage 2 depending on the bike and the distance (directly behind is generally always stage 2). Some of the local ghetto hoodrats driving by almost never bothers it.

Don’t forget to remove the ground strap again before doing any more wiring.

Blinking lights!

Typically, you would normally do things like this last as they’re sort of a luxury – they’re not really necessary for the operation of the vehicle. However, I reasoned that while I had the dash apart I might as well do it because it was easy. Yeah…

I scratched my head staring at the wiring diagram of my truck for quite some time, before I figured out how I was going to wire them. On my truck, the front and rear turn signals go through two different flashers, I’m assuming because it has a factory tow package and the rear has a heavy-duty flasher for trailer lights. Chevrolet’s flasher logic seemed pretty complex to me – at least for a 1985 vehicle – but it’s possible I had just been staring at it too long.

I finally decided that the best way to do it would be, since I was under the instrument panel anyway, to go to the turn signal indicators in the instrument panel. Note this won’t work on all cars, it all depends on the flasher logic the manufacturer used. In my case, it only makes the front lamps blink – but that’s enough for now.

If you’re going to hook up to the left and right turn signals, you want to be absolutely certain you don’t accidentally bridge them! To accomplish this, a good set of heavy diodes (my alarm kit was nice enough to include them – maybe yours will too) can be used. To the right you can see the diodes wrapped up neatly next to the wiring loom, after splicing, soldering, and wrapping with tape.

Note also, that I thoroughly discourage hooking the wires directly to your headlights. There’s a few reasons for this. Firstly, if you’re foolhardy enough to hook the tiny little wires directly to a wire that feeds the headlights, you’ll burn through them (and quite possibly your alarm module) in mere seconds. If you hook it up through a relay, and your car has a poor electrical system, you could flatten your battery sufficient so the vehicle won’t start. Again, it’s entirely up to you, but I just don’t think it’s a good idea.

Door Unlock

As I said in the introduction, my car already has electric door locking, which means I don’t have to install solenoids. The trick is, figuring out what wires to hook to where. Unfortunately as I’m writing this it’s been a good month since I initially did this part of the installation, and I’ve since forgotten what electric door lock system my car has. I believe it’s positive switched relays, but you should do your own research anyway.

Your alarm system will have probably three or four wires for lock, and the same number for unlock. I found it easiest to thread the wires that I needed through the conduit into the driver’s door, and attach to the lock controls inside it. Don’t forget to tape up the wires you aren’t using (or remove them completely if you desire).

If I find time, I’ll research it again and replace this section with something more informative.

Hood pin switch

Hopefully you’ll find a “normally opened, goes to ground” trigger wire on your alarm, that you can send forward into the engine bay. Again, stealth is key. Then, find a suitable location to mount your pin switch – I put mine all the way on the right hand side, far enough back that no one could hold it with their finger. You’ll need to adjust the pin so that it doesn’t make contact while the hood is closed, only when the hood is raised.

This step is especially critical for alarm models with remote ignition – you really don’t want the possibility of the ignition being tripped while you’re changing a fanbelt do you?

Starter Kill

I like to take a different route with the starter kill. Because a typical starter kill can be disabled with so much as a screwdriver or wrench across the soldenoid terminals, I find actually killing the starter to be pretty much a useless exercize to discourage a decent thief.

Instead, and your mileage will vary wildly on later model cars, I like to kill the ignition system, on or around the coil. By using the supplied relay to switch off the power going to the coil, hotwiring your car becomes a frustrating exercise. Again, stealth is key – and I’m not completely done obscuring my job. I’ll post before and after photos once I’m done.

An alternative on this on some later model cars is to keep the starter kill wire inside the cabin, and simply attach the relay inline with the fuse for the fuel injectors. An EFI vehicle will not go anywhere without power to the injectors, though you will want to speak to a competent auto electrician to ensure this won’t do any damage to your engine computer!

It’s things like this, where each install can vary from job to job, that make car alarm installations more effective. If a thief has a mental blueprint of your car alarm layout in his head, then normally within about 5 minutes he can get around all the roadblocks you put in place. When you change things up a bit, and do things a little different, it makes all the difference in keeping experienced thieves in your parking lot instead of on the freeway with your car.


I really can’t stress enough how stealth is key when it comes to wiring. If you place all the components in good, secure locations, then the wiring is the next obvious vector of attack. If you are restoring a vehicle, down to the electrical system, including alarm system wiring in your looms, and wrap them together to make the wiring for the alarm almost indiscernable.

The battery is also an often-attacked location, it might make sense to have a contingency plan. I’ve often thought about using two “dolphin” flashlight batteries as a backup power supply – give it some creative thought. Armor around the battery wouldn’t be a bad idea, even so far as some sheet metal that requires a few nuts to be removed would make things a lot tougher.

There are two goals in alarm system installations. The primary goal is obviously keeping your vehicle in your posession. The secondary is minimizing the damage to it. If you decide to armor plate certain “soft targets”, ensure that in doing so you make it as menacing as possible. If the situation looks hopeless, most thieves will abandon the vehicle and move on. It should be mentioned that an armor-plated steering column not only makes your vehicle look like it’s tough to steal, but it also gets you discounts from most insurance carriers (as does an alarm).

Well if you’re still with me, hopefully you found this article interesting.

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