alarm malfunction how does this happen?

I bought a truck with an alarm installed, but it wasnt working and the previous owner didnt know why. I replaced the battery in the keyfob, and an LED lights up whenever I push a button so its getting power. I poked around under the dash and I have a cpu, shock sensor and probably some other goodies that go along with the alarm. when I disconnect and reconnect the negative battery cable, the alarm goes off. the keyfob doesnt turn it off so I have to put the key in the ignition and turn it to the On position (just short of cranking the engine) and the alarm turns off.

it looks like the alarm cpu unit is working. when i tap the shock sensor, LEDs light up on it. the keyfob led lights up when I push any of the buttons.

The whole system, however, isnt working together. as to whats going on here, i'd guess the previous owner dropped his keyfob in liquid and thus i'll have to get a new one.

You probably will need a new transmitter if he dropped it in water. What is the exact make and model of the system?

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Installer, IT support, and FFL. I need less hobbies.

Need more info

1. Most (not all, but most) alarms will go into full trigger if the car's battery is disconnected and reconnected.

This is probably for two reasons: A, the alarm isn't "smart" enough to remember its disarmed state before you disconnected the battery......and B, so that if a car thief tries disconnecting and reconnecting the battery, he still can't steal the car.

2. Seems like for whatever reason, the remote transmitter and the alarm's brain aren't communicating. Here are your possibilities:

A. Bad remote. The LED can work, but the remote can still be bad.

B. Remote has somehow come un-programmed. If you can figure out the brand, maybe one of us here can tell you how to re-program it. Any name on it? Maybe a phone number on the back of the remote?

C. Most alarm/remote start combos, as well as a few alarm-only units, have a separate antenna that is attached to the windshield glass. They do fail every now and then.

(Most basic alarms use a simple piece of wire as an antenna. Even if the wire breaks or is cut, the alarm would still work, just with poor range. Have you tried the remote while sitting inside the car?)

Also..turning the key should NOT in itself turn the alarm off..It should turn off by the remote or an over-ride switch in conjunction with the key..the exact sequence and procedure will vary from system to system..but disarming by turning the key is not normal for an aftermarket system unless it uses an old style toggle and the valet is on. Older systems were less complex and sometimes simply turing the key and flipping a toggle would disarm it.....unfortunatly this made it very easy for a thief to disarm it as well.

Get to the "CPU" and see if it has a brand name on it..possibly we can help with re-programming the remote. However we need more info or we can just guess all day and still get nowhere fast.

See ya back soon.

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The thing is, i'm not 100% sure what alarm system it is. I did a google search of the FCCID number on the back, which is PATTX3UTEK and it looks like its a Falcon alarm fob. the remote has an F on it, heres a picture of it:



and i'll start digging out the cpu today, its ziptied onto a metal tube under the dash, near the steering column. I'll see if there's any markings or identification on it.

I've tried using the remote while sitting inside the car yes, again, nothing happens. I dont see a toggle switch anywhere (valet switch). The truck itself is a 1998 F150 and I'm pretty sure the previous owner had it installed soon after he bought it so we're talking about a possibly 9 year old system. it does, however appear to function well and I dont want to spend money on a new one if I can help it. If you guys could help me reprogram the remote that would be great! is there any way to test if the remote is sending out a signal?