1990 Chevrolet Corvette, Avital 2101 Remote Keyless Entry Versus Factory Alarm

Hello friends. I still check-in from time to time, but the cars being discussed now are too new for my experience, so I seldom post. I have an odd one...

I'm installing a 2101 RKE only in my personal 1990 Corvette. All has gone well, it is working. But there is a quirk.

The factory alarm (UTD) arms by door open, lock with power locks, close the door. Universal Theft Deterrent is armed. To dis-arm, unlock either door with outside door key. (I have the 2101 grn/blk FAD wire connected to this car's wire). The system is contained within the CCM (BCM). If the UTD is armed, the horn will sound when the CCM receives any of several "wake-ups" which include an UNLOCK, or LIGHTS ON.

When I arm the UTD, if I UNlock with the 2101, the horn briefly (perhaps 40ms) sounds, and the doors unlock normally. What I think is happening is that the UNlock pulse is being sent ahead of the FAD pulse, and the wake-up is triggering the horn, then the FAD pulse arrives and the system disarms.I know it is the car/CCM doing the honk because I haven't yet connected the 2101 brn horn wire or light-flash wire.

Can any one suggest a solution to delay the UNlock pulse for just a few milliseconds. Like a capacitor or something?

Thank You for reading.

If it's a small delay, you might just try connecting the unlock wire to a relay and using the relay to trigger the factory unlock.

A guy that used to post in here went by "hotwaterwizard" was really good at that kind of stuff:

https://www.the12volt.com/installbay/forum_posts.asp?tid=124243

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My ex once told me I have a perfect face for radio.

I thought that the Disarm Pulse was usually before the Unlock pulse but that might vary by Manufacturer and Model. I never checked it with a dual trace O'Scope but remember determining that GWR precedes IGN output one time.

If the added relay trick doesn't give enough delay...

While slightly more expensive, here is a link to a small PCB that should give you the delay you want on the Unlock Pulse. It runs on +12V so there will be some at rest current draw.

EBay search on : DC 5V 12V 24V LED Display Digital Delay Timer Control Switch Turn ON/OFF Module

Using P8 Mode, it would use Unlock as the input trigger. You can set a T1 delay until the onboard relay would energize and give a (-) output for the pre-set T2 time. Lastly set the Cycle to 1 for just one (-) output.

I think I remember where instead of messing with the Unlock pulse an installer just interrupted Horn power or signal during the Disarm and Unlock sequence.

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Soldering is fun!

Thank You both. I also thought that the FAD pulse was ahead of the UNlock pulse. It may have been something else, now I'm not certain what it was.

I'll leave the opening post up unedited, but the situation described has only happened twice, including the very first time I tried it at 2300hrs with my neighbor's bedroom window about 25 feet from my work area. Woops.

There is one mode that I know the horn-honk will be a problem. If I arm the UTD with LOCK then close the door, the UTD arms 2 seconds later. The CCM goes to sleep. If I push LOCK again, to be sure it's locked, that will be a wake-up for the CCM, and the alarm will trigger. I'll just have to learn to not do this. OR close the doors, LOCK with the fob and walk away. The UTD will not arm with the doors closed. I did install GWA protections, so these will be active when locked with the fob. My main concern is to protect against drive-away theft. Entry alarm is secondary, and not a real concern of mine. Honking horns just annoy people.

Thanks again for your interest and participation.
DaveP