Keyless Entry, Control Head Unit Power, PAC TR7

I have a project surf van I am blinging out a bit. I just fitted an eBay keyless entry into the old girl after a mid range Sony head unit some Focals in the front some JBLs in the tailgate and a 10 inch sub under bed base. The Chinese keyless entry radio has a spare temporary +ve pulse wire to trigger boot release. Could I use this pulse to trigger a latching relay to supply power to the head unit? The idea is to be able to close the front doors and keep the tunes going while getting out boards and putting on wetsuits and shut tailgate and have the key fob lock all the doors and power down the stereo as I’m walking off. Vice versa when returning to the vehicle and unlocking it. I also like the idea of being able to locate my car in a parking lot by walking towards the sound of Metallica blaring. Cheers from down under Henno

Yes you can. If your keyless module can not be switched to a negative output on that wire, you can use this diagram but you will need to use a 5th relay to convert your positive out to a negative out. Simply replace the pictured push button switch with the 5th relay. This along with this to convert positive to negative

Alternately get a PAC TR7 universal trigger module - about $20 on Amazon https://catalog.pac-audio.com/index.php?controller=attachment&id_attachment=68

This looks like good but it says it’s rated for 2 amps only. My head unit is hungrier than that.

i am an idiot wrote: Yes you can. If your keyless module can not be switched to a negative output on that wire, you can use this diagram but you will need to use a 5th relay to convert your positive out to a negative out. Simply replace the pictured push button switch with the 5th relay. This along with this to convert positive to negative

This looks good for current draw but what is the value of the diode? I’m sure there is a spare neg output pulse.

The red wire of your radio draws Milliamps of current. 1000ths of an amp.

henno wrote: This looks like good but it says it’s rated for 2 amps only. My head unit is hungrier than that.

You can use the TR7 to drive a relay to power your HU. You would typically only activate the HU via its ACC input whose current draw is minimal.

OK. So I have a PAC TR7 on the way. Next question is can i then switch between my remote power supply triggered by the TR7 and the standard ignition power using a SPDT switch? The reason is I leave my car unlocked at home (sleepy country town on acreage) and don’t want the head unit on all night at home so would like the advantage of flicking it back to normal so my ignition will kill it. I’d prefer it to be a rocker switch but the only ones I seem to be able to find are on/off/on and I would prefer it to be on/on so it was one or the other with no off option in the middle.

Has anybody got experience setting up one of these TR7s? There seems lots of advice on how to use them to watch Alpine DVD players while you’re driving. I want to set up mine to latch the output on to turn on my stereo head unit when it gets 2 pulses from my remote entry receiver unit that go to my flashers/blinkers on unlocking the doors. Then unlatch to turn off head unit (1pulse from blinkers) when I lock doors. I can set it up to go into Feature 13 by earthing the brown wire 13 times and getting that many flashes back but,,,,. The next step where I have to set it up so 2 pulses = on and 1 pulse = off is doing my bloody head in! I tried feature 3 as a standard one pulse latch but none of the outputs from the keyless radio would get it on and off how I wanted every time. Feature 13 using the hazard/blinker pulses is good because there is a known difference between the on and off commands so I can’t get it out of sync if I double push a remote button.

So my mad scheme to have my head unit turn on or off using my keyless remote works with a glitch. I have the PAC TR7 set up to be triggered via its green pos input wire connected to the brown outputs that supply one flash to turn signals for lock and two for unlock. Problem became apparent when I took it for a drive and put my turn signal on and it turns off my stereo! Hilarious really. Is there any way the brown outputs from the keyless entry radio (still connected to input wire of TR7) can still pass their pulses to the lights but the inputs on that same wire coming from my hazard button or turn signal stalk don’t get their pulses back to the TR7? Would it be as simple as a diode in-line? If so what value or is their a preferred auto component for this task?