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Premium Member
2019 Subaru Forester Limited CVT
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37 Posts
Discussion Starter · #1 ·
Hello there! I noticed the Forester has a cool feature that keeps the radio on for a short while after you shut the engine off until you open the driver door. I really like this feature and wanted to keep it.

I have added amplifiers to my Forester and tapped the ACC wire behind the factory radio to run my amplifier remote turn on wire. However the amps switch off as soon as you shut the engine off while the radio still remains on until you open the door.

I was wondering if anybody knew If there was a different ACC wire I could tap to keep the the amplifiers on while the radio is on?
I'm guessing there has to be a second wire somehow connected so the radio knows when you have opened the door so it can shut down. I've looked through the wiring diagrams over and over again and to see no magic wire to accomplish keeping this feature.

Thank you very much for any help you can provide!
 

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2018 Forester MT
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73 Posts
Assuming the 2019+ models use the same "Toyota" style large 10+6 pin power/speaker connectors, check either pin 8 or pin 9 on the 10-pin, one of those should provide a 12V output for the amplified radio antenna that remains powered until the door opens that you could tie your remote turn-on wire to.
 

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2019 Subaru Forester Limited CVT
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37 Posts
Discussion Starter · #3 ·
Thank you very much for your reply. Yeah it uses the same old Toyota harness. I tried the antenna wire and for some reason it didn't switch on the amps. I did a voltage reading of it and it reads 9.6v. I ended up using pin 3 of the 10-pin harness, the ACC wire but that's the one that shuts off directly with the ignition. I'm going to check out that antenna wire again just to see if I didn't get a bad reading.
There is a 28-pin harness that also plugs into the back of the factory radio. I'm suspecting the magic wire might be in there somewhere unless it's controlled by the canbus?
I've seen the three relay latch on the 12-volt .com but that seems a little extreme. I was hoping there would just be a wire back there that lets the radio know you opened the door. I'll let you know about the reading that I take again from the antenna wire. I was a little curious that it was 9.6 volts.
 

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Thank you very much for your reply. Yeah it uses the same old Toyota harness. I tried the antenna wire and for some reason it didn't switch on the amps. I did a voltage reading of it and it reads 9.6v. I ended up using pin 3 of the 10-pin harness, the ACC wire but that's the one that shuts off directly with the ignition. I'm going to check out that antenna wire again just to see if I didn't get a bad reading.
There is a 28-pin harness that also plugs into the back of the factory radio. I'm suspecting the magic wire might be in there somewhere unless it's controlled by the canbus?
I've seen the three relay latch on the 12-volt .com but that seems a little extreme. I was hoping there would just be a wire back there that lets the radio know you opened the door. I'll let you know about the reading that I take again from the antenna wire. I was a little curious that it was 9.6 volts.
If the antenna wire is switching on and off at the right time, but the voltage is low or it can't supply enough current, you could use a solid state relay such as this one:

Relay example

These generally will switch on at 3- 4 volts, so the 9.6 volts to the antenna would feed the control+ input, with the control- grounded. The switched terminals would be wired between the amps and any convenient 12 volt source.
 

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Premium Member
2019 Subaru Forester Limited CVT
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37 Posts
Discussion Starter · #5 ·
I measured the antenna wire again and still got 9.6 volts. It seems to stay on for a while after the radio shuts off for some reason. I had the multimeter on it and after I opened the driver door (after the ignition was shut off) it remained on. I checked it 5 minutes later and it was still on providing 9.6 v. 9.6 volts seems like a strange voltage to go to the antenna so I replaced the batteries and tested the multimeter out on other voltages and it works fine. I was starting to think the multimeter was wonky. Thank you all for your suggestions!
I keep looking at the wiring diagrams trying to figure out what switches the radio off when you open the door. I am completely puzzled. I think it's cool feature and I would like to keep it. Something has to tell the radio to switch off when you open the door. I'm thinking at this point it might be the canbus?
I would love to hear more ideas if anybody has them! Thank you to everybody who has replied.
 

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2018 Forester MT
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73 Posts
That is quite odd, but considering the changes with the new models I can't say it is too surprising with the new LTE communications. Back when I was researching for an aftermarket radio installation, I saw on WRX forums that the door signal is provided on a single blue wire leading to a 12-pin plug, does that exist on yours? Otherwise it is likely one of the wires going to the 28-pin aux connector, or CANbus controlled
 

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2019 Subaru Forester Limited CVT
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37 Posts
Discussion Starter · #7 ·
I don't have a 12-pin plug on mine. I've got the 10-pin that has the power and ground plus front speakers and the antenna. The Forester only uses 8 out of 10 pins on that harness. There's the harness for the rear speakers and one for the backup camera. Then there's that 28 pin harness that has all kinds of goodies hooked up to it but nothing in that harness seems like it's hooked up to the door switch or anything near it unless it's on a different wiring diagram. I only happen to have the diagrams for the head unit and telematics module.
I'm going to try to probe some of the fuses in the fuse box but I need to recruit a helper to make that happen. You need about five hands lol to hold the probes in place plus push the ignition switch and release the door switch. I'm hoping maybe one of those fuses might stay on until the door is opened but I'm kind of doubting it.
It's curious that you found on the WRX forums about the blue wire that has the door signal. It seems like that's exactly the wire I'm looking for! I wonder if it goes into the 28 pin harness on mine somewhere?
 

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I measured the antenna wire again and still got 9.6 volts. It seems to stay on for a while after the radio shuts off for some reason. I had the multimeter on it and after I opened the driver door (after the ignition was shut off) it remained on. I checked it 5 minutes later and it was still on providing 9.6 v. 9.6 volts seems like a strange voltage to go to the antenna so I replaced the batteries and tested the multimeter out on other voltages and it works fine. I was starting to think the multimeter was wonky. Thank you all for your suggestions!
I keep looking at the wiring diagrams trying to figure out what switches the radio off when you open the door. I am completely puzzled. I think it's cool feature and I would like to keep it. Something has to tell the radio to switch off when you open the door. I'm thinking at this point it might be the canbus?
I would love to hear more ideas if anybody has them! Thank you to everybody who has replied.
Looking at the diagram, the door switches appear to connect only to the Body Integrated Unit. For example "D SW (D)" is listed as the designation for "Door switch (driver's seat)". So they are probably using CAN Bus. The antenna power wire must be the one labeled "ANT-ON", which also powers the SiriusXM antenna. Perhaps they chose to keep those powered for a short time, but you could probably still use a relay with that to power the amps, as long as they don't stay on long enough to drain the battery.
 
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