Hello everyone, thank you all so much in advance for your help.

I recently purchased a home that has a bit of a unique situation with its security system so I’m in a predicament and could definitely use your help.

The home was built in the 60s, but had an Ademco 4140 installed circa 1989 with quite a few wired sensors installed. From what I can see just by looking around my house, it looks like there are 5 window sensors and two door sensors that appear to be “wired up”.

There were more sensors, but various windows and doors were replaced over time and the sensors were stripped out. But it looks to me like two of the three doors have wired sensors on them, and five windows have window sensors. There is also a huge siren horn in my attic that is wired up to a siren card in the 4140 panel.

But something I think a little odd happened. A few years ago, some contractor came in and basically cut the power to the 4140 motherboard and replaced the Ademco keypad with a Honeywell wireless system, I think a Lynx 3000 or something similar. I thought this very strange, why cut off all that infrastructure installed? Plus, for those two doors I noted above have wired sensors attached to them? When the contractor “upgraded” this system, they tacked on new wireless sensors. Strange.

Anyway, a second wireless system basically got tacked on top of the wired one, the wired one was basically shut off, but the wireless system was much, much more stripped down. That system basically has only three door sensors, one motion sensor, and one fire detector.

The problem is, over time, since the Lynx was installed, most of the wireless sensors have broken. Proximity sensor doesn’t work, and two of the three door sensors lost either the sensor or the magnet. Fire detector has a dead battery. The way the Lynx system currently is, only one door sensor actually works, nothing else on the Lynx works.

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I would like to DIY my security system upgrade. The question is what should I do?

• One option could be to take a multimeter and test all the wired sensors. The original installer thankfully has tags on all of the wires. Each of the wires also has a resistor attached to them (I assume EOL resistors (even though they’re at the panel?), not sure, yet). I plan to test the continuity over the next week. If the two doors and five window sensors basically work, one thing I would be tempted to do would be to replace the 4140 motherboard with something new. Probably a Vista 15P or 20P. However, because some doors and windows in the house have been replaced, I would need a new motherboard with a RF transceiver added so that I could have some wireless capability as well. At the very least for the backdoor to the house. I have gates in my backyard as well, would love to add outdoor-compatible wireless sensors there as well.
• Another option would be to replace the Lynx with an upgraded Honeywell wireless system. But as I noted above, almost none of the wireless contacts in my house currently work, so I would essentially need to repair/replace everything, all the wireless sensors.
• Another option would be to scrap everything and get something just consumer-ready (like a Ring system).

Options 2 and 3 seem like I would be basically wasting the wired infrastructure already in the house. Option 3 also seems like it wouldn’t add much value to the house. I think a mainstream system would be more valuable with regard to the resale of the house.

But option 1 seems a little daunting and most likely the most expensive option because (i) I would still need some wireless capability so I wouldn’t “just” be buying a 20p, and (ii) I would be reactivating sensors that are 35 years old and haven’t been used in 15 years. Will they work? If they don’t work, the 20p motherboard would be a huge waste because I don’t have the time or $$ to push new 22 AWG through my house. I won’t be able to do that. But the multimeter tests should help to determine if they work.

I want to DYI the install. I will probably work with a no-contract monitoring company once I get everything going, but my goal here is to be in complete control of the hardware and the equipment. I know generally what I’m doing, I know how low voltage works mechanically, but I’m not an expert. It will take time. Lastly, regardless, I would like to minimize any drilling/drywall cutting. I would really need to use the wiring already in place if I get a new 20p or equivalent motherboard.

Another interesting thing: the 4140 motherboard shows that there were wires for two keypads leading into it: one in the family room, one in the master bed. Both of these keypads are gone. I would love a new keypad in the master bed (currently the Lynx is in the family room and is the only keypad in the house) along with the one in the family room. But I’d need the master bed one to be wireless. There aren’t any wireless keypads that communicate with the 15p or 20p, are there?

Thank you again!