Remote RF Control For Rear Hatch?
 

I’m thinking that it would be pretty nice, as I approach my car with an armload/basketload of groceries or other items, to simply press a remote switch to activate my car’s electric hatch lift switch.

Also, as a photographer using some pretty expensive gear, I really don’t like having to put this stuff on the ground in a dirty/wet parking lot in order to open the hatch manually.

Plus, no matter that I've cleaned and lubed my hatch pin receiver plates, the effort required to turn the key to open the hatch manually still has me thinking that its only a matter of time before the key starts to bend and perhaps break.

Seems like it should be really simple to graft a remote (RF) momentary switch into the rear hatch circuit. Lots of inexpensive kits available online, in key-fob form. Has anyone here done this?

If you wire a remote momentary into the circuit for the hatch release motor, should work just fine. Just be careful with the amount of parasitic draw from the receiver.

Make sure you document the installation for the next owner.

It's not quite easy, you can't just parallel the remote with the switch. This is because the switch also handles part of the motor braking function, which shorts the windings when the motor gets to the stop position. You'd need to change out the existing switch for a SPDT relay, then activate the relay with the the switch and remote in parallel.

Remote Hatch Catch Latch Release
 

I've actually been working on a wiring diagram to add keyless entry to my 924S. Here is a snippet of the circuit for connecting the keyless entry controller to the hatch button circuit, with an interposing relay (added in blue). The brown wire is momentarily grounded to energize the circuit (via an auxiliary output on the keyless entry controller), similar to pushing the button. Note that this piggy backs on the existing without defeating the manual pushbutton.

http://forums.pelicanparts.com/uploa...1634781379.jpg

This is exactly what I was thinking...to piggyback into the existing circuit so the car's existing pushbutton would still function as usual.

I'm not great with these electrical diagrams (even though I've wired a house), but I think it will eventually make sense.

There are a number of RF switch units on the market...and my assumption is that I'd want something which will work with 12 volts...but what about amps? Many units are rated at 10 amps, which I assume would be sufficient...although maybe I'll look at the fuse for this circuit to verify this.

At any rate...thanks for the diagram!

The circuit is fused at 25A for both old and new cars. I don't know what that motor actually draws though.

In the older cars, the fuse is shared with the fresh air blower (heater blower.) In thinking about this today, your could turn off the blower, swap the fuse out with an 8 amp version, and pop the hatch and keep the release running for a bit to see if the fuse holds. It's going to draw maximum current while trying to release the hatch since there is additional friction in the release mechanism when it is closed. This would be a clue that a 10amp relay might work.

They make SPDT remote relay modules. This could be used as the relay in the above diagram, provided it can handle the current. There would be no need to for anything additional to make or break the ground.

Shower thought: You might want to add a relay to kill power to the remote module while the ignition is on. I don't know how good a cheap Ebay module is at spurious signal rejection, or other possible engineering concerns. Popping the hatch at speed would be "interesting."

Hmmm...sounds like a good idea!

So, just for giggles, I did a test on my 86 951 (should be the same as your 84) with my power probe (a great tool, check it out) and, with a momentary pulse to pin 53 (red wire with a white stripe) at the red connector near the hatch release motor, I was able to make it cycle one time, accomplishing the unlocking. Judging by the diameter of those wire, probably 5 amps or less.

I'm going to order an amazon remote switch, just to check it out. Probably worth $15 for the fun and additional knowledge. Will post more later.

You know what would be cool. Replace the hatch struts with linear actuators and get rid of the pins completely.

Amazon screwed up the order... project put on hold, but definitely doable and simple to tap into the wiring for the motor connector.

I may consider doing it in the spring/summer.

Too bad about the Amazon order...but I'm also thinking that this would make a good springtime project.

I'm guessing that the mechanism would be the same on my '87 as on your 86 951, and that grafting in the remote switch near the hatch motor would make sense. It also sounds like the existing cabin switch would still work.

At any rate...in the meantime - I will check out one of those power probes, and if I decide to jump into this project before spring...I'll post some results, but otherwise, I'll look forward to knowing how yours has worked out.

Amazon dropped the ball on my order too. Shame. I've got an Aliexpress order in, so maybe in a month or two.

Jeeesh...looks like I need to get with my own program and order some parts!

Which one(s) did you guys order, by the way?

Amazon calls it: QIACHIP DC 12V 1CH 433Mhz RF Wireless Relay Remote Control Light Momentary Switch Transmitter with Receiver (1relays)

I'm all about the safety of disabling the remote with a relay with the ignition on. I was originally thinking that there is no ignition signal at the rear, but I eventually realized you might be able to route the fuel pump power into the cabin somehow in order to disable the remote. Fuel pump not running would be a reasonable proxy for the car not moving, and being able to safely pop the hatch.

I'll probably mount mine near the switch since the ignition on signal is available nearby.

Got my Amazon remote relay... pretty spiffy for $10. Bench tested it with a 12 v power supply and a VOM to check for load switching, and it is surprisingly robust. All I need to do now is tap into three wires at the motor and watch the magic happen!

George...please keep us posted!

BTW - which unit did you purchase from Amazon?

I do wonder about Mr. Original's concern about RF interference. Would hate to be cruising down the highway and suddenly have the hatch opening up or at least flapping in the wind!

At any rate...good luck!

I got the one that originalowner identified in a prior post.

I scanned in the instructions and highlighted the pertinent sections for the 944 hatch. You can download the pdf here:

https://drive.google.com/file/d/1uvK3RuZzRnFWjlJNK8OyC9iJYLyuHM9_/view?usp=sharing

I'm not too concerned about the rear hatch becoming unlocked while driving. The hatch is not designed to raise up by itself, that only happens in the case where the hatch shocks are too strong (that's only one of the problems, the glass delaminating from the frame is the more serious consequence of too strong hatch shocks.)

I guess I was thinking more of a possible RF signal from another source inadvertently activating the circuit and causing the hatch to open or at least unlatch itself. But maybe this would not be an issue?

Mine still hasn't come, even though I ordered before you. :( Can you check the quiescent current? I'd like to know how much it draws while waiting.

never mind

never mind

George, I don't know how that is working for you. You must have a new style car as the wire colors do not match my older one. Looking at the newer schematic, I find the following: Injecting power into the red/white wire should short out with the motor in the park position. The current travels through the normally closed contact of the manual switch, then through the white wire to the park contact of the motor, to brown and to ground.

I'd be really leery of what you have hooked up. Some variation of the schematic in post 4 is needed. Again, if/when I do this, I will add a disable for when the ignition is on for safety.

never mind

I've looked at the 86 Turbo schematic, page 4. My comments stand.

Never mind

George that looks great!

Question: How does the unit operate with the remote a bit farther away...say five to ten feet - starting with the hatch closed?

never mind

Measured standby current for the module is 5.9mA. Not quite in spec, but not really worth worrying about. Looking forward to installing it soon.

BTW, I had an epiphany in the night a few days ago. The perfect signal for disabling it while the car is moving is the automatic sunroof lock signal. Since this is available very nearby the motor, I'll be putting my module in the rear as well now.

Working perfectly, installed per onZedge schematic plus added relay to cut power from sunroof lock signal (grey with black stripe on both old and new schematics.) Does not operate with vehicle moving above threshold speed.

Wire colors different on the 1986 944 turbo
 

Thanks for the information guys, but I wanted to give a heads up for others that the wire colors you specified in the wiring diagram are different at least for my 86 951. It is worth checking your installation as it makes a difference!

I've been working on installing a keyless entry/ alarm system since the original alarm cratered and I thought I might as well automate the hatch as well. My installation matches the "Sheet 5" (HVAC, seats, wipers) and uses Blue for power in (pin 2/ NO position), White for NC position (pin 3), and red/white for Common out (pin 1).

http://forums.pelicanparts.com/uploa...1641081378.png

I was still able to use your suggested wiring after ordering a relay from Amazon. Works great when I manually ground the "85" wire, and when I use the original switch. Now I just have to figure out why the new alarm system is not grounding the output when I hit the trunk release button...

Sorry - I posted without seeing all of this discussion as it was on page 2... Seems like I noticed the same thing that you did, only a few months later.
I was able to get the alarm to work - turns out I needed to hold the button down for 3 seconds. I updated all of my wiring diagrams after getting things where I wanted them. The subject portion is below.

http://forums.pelicanparts.com/uploa...1641483442.PNG

Nice to have this thread come back to life...and I'll look forward to making this (remote hatch lift) mod when the weather here warms up a bit.

Thank you!!!

Thank you so much for posting this schematic. I just bought one of the cheap $10 units off amazon and a cheap relay that actually fit inside the plastic housing of the keyless entry unit. Your diagram was perfect. Brilliant for coming up with this!!!!

I actually built an intermediate harness that plugs into each of the molex connectors (switch plug and harness plug) and did my wire cutting/splicing between my two plugs so as not to cut into any of the original wires on my car. That way it can be put back to original just by removing the harness I made. Now I just need to be able to fish it down from under the dash to the hole where the switch clips into.

@ELew502 - I have an 86 951 as well and I did notice the difference in colors for wires too - I just used my multimeter to determine which wires go where on the relay in reference to the original switch functions.

I am highly skeptical of this idea. I have trouble getting my hatch open with a key, let alone with the switch. Also mine does not raise up by itself when unlocked. I open it with the key, manually raise it and use a prop rod.

This is the way.

I wired mine in at the back.

if the relay that comes with the remote switch is too small you can always piggyback on a larger relay. In that case the relay simply runs the pull in coil of a larger relay with higher amp contacts.