Adding keyless door unlock to central locking system

[notny41]

@Tom, I thought you had made a comment one time about how you added a cheap keyless lock/unlock remote system to one of your 944's one time - I wasn't able to go back and find that post unfortunately.

I'm going to be adding all of the components for the central locking system into one of my 944's and while I'm doing that I figured I'd go with one of the cheap amazon universal keyless entry systems as well.

I found one that was inexpensive but yet had pretty nice looking simple remotes and did a little testing with it. seems like it should work fine.

My question is: is there a way to tie into the 944 wiring in an elegant way? I need to tie into the door lock cylinder switch as well as the parking lights to give a visual indicator from a distance of if the button-press was recognized by the car (unfortunately the system I bought has a negative output for trunk release - I think I would need a positive output for that so I probably won't be utilizing that feature).

[Tom]

Yes, I did add a cheap-o door lock remote to my 944 -- has worked like a champ for years. My car started with central locking, so basically everything was wired and ready to go. It's been a very long time, but basically the system has a little receiver box you hide under the dash. It has two wires -- one that triggers ground when you push lock, and one that triggers ground when you press unlock. If memory serves, you just tap those wires into the lock and unlock wires going to the switch above the shifter, and that's it. You leave the original wires all hooked up to the switch, so it still works, and the remote just adds a second way to trigger ground on the lock and unlock wires. Make sense?

[notny41]

Yep - just was wondering if you found a way to wire it without cutting into the original harness of the car.

Not even sure how a person could do that unless you had an intermediate connector somewhere in the system...

Did you hook up your parking lights for visual confirmation?

[Tom]

Yep - just was wondering if you found a way to wire it without cutting into the original harness of the car.

Not even sure how a person could do that unless you had an intermediate connector somewhere in the system...

Did you hook up your parking lights for visual confirmation?

No on the lights -- good idea though. My remote came from Circuit City, if you are old enough to remember them (kind of the pre-curser to Best Buy) and had a million outputs for those kinds of things, but I just focused on operating the locks for simplicity.

Mine is not exactly this one, but very similar to this $16 unit on Amazon:
https://www.amazon.com/FICBOX-Universal ... 213&sr=8-7

The harness in this car have been tapped more than a 20 year-old beer keg, so I had no problem stripping off a little insulation and tapping in the remote's wires. If you wanted to avoid that, you could just make up little bridge wires with a male bullet connector on one end (that goes into the harness connector) and a female bullet connector on the other end (that goes onto the factory switch posts shown below). You could then connect the remote to those bridge wires as needed without modifying your original harness at all.

switch.webp (1.6 KiB) Viewed 1133 times

Or, if you wanted to get fancy, you could design and 3Dprinted bullet connector housing akin to the one below to create a slick patch harness in lieu of individual wires. I'd say you could just got the connector off any old 944 harness, which would work for the harness side, but you'd still need to come up with a connector for the switch side.

https://www.carpokes.com/viewtopic.php? ... ann#p27837

[944er]

Or, you could simply use t-taps to tap into the existing switch wires. You could use the hatch release negative output to drive a relay, with the other side of the coil on positive voltage. There was some discussion on Pelican a couple of years ago on how to go about wiring into the hatch circuit.

[notny41]

@944er - I thought about that too. May still consider doing that. I think I have a generic 12v relay laying around somewhere.

[notny41]

I think you are onto something @Tom - I might just take the back off the door harness connector and solder on a wire at the pins needed and then I don't need to make any cuts.

locks harness connector.jpg (993.42 KiB) Viewed 1112 times

[Tom]

I think you are onto something @Tom - I might just take the back off the door harness connector and solder on a wire at the pins needed and then I don't need to make any cuts.

locks harness connector.jpg

That works electronically -- I'd just check before soldering to see if the cover will still clip on. Those things are often a super tight squeeze around the wires, and adding 2 more wires might preventing it from clipping shut. I generally avoid those vampire tap things, but for something like this where a super clean connection isn't critical, I'm sure they'd work fine too. I just wouldn't use them on stereos or engine management signals...

[notny41]

@Tom, do you recall where you connected the +12v power for your keyless entry box?

[Tom]

You could use the cigarette lighter power wire, which is always on (at least on my car), but there is also an always-on wire in the factory radio harness and for the clock. I can't honestly remember where I got power on my car, but most likely one of those, or a wire with in-line fuse going straight to the battery. the cig lighter is designed to carry lots of current, so has plenty to spare for this, but these units generally draw very little current (to reduce parasitic drain) so even a low-amp circuit is most likely fine.