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Loose connections are always known suspects - been there multiple times So make sure all connections have good contact.
You've tied together the HU Red and MOST Red with the HU blue/white wire => this is an issue.
Blue/White is an output from the HU and the HU Red wire is an input to the HU.
HU Red should be connected to the fat Red wire coming from your HVAC orange wire. Nothing else to be connected to this fat red wire.
HU blue/white should be connected to MOST Red wire. Nothing else should be connected to the MOST Red wire.
These are 2 different circuits. Do not combine them.
The yellows and the blacks look fine.
There is a difference between the yellow and red wires. The yellow wire is what supplies power to the HU and the MOST Box.
If you notice it will be much thicker than any of the red wires.
The red wire is just used as a switch - to signal devices to turn on and off. In some cases those devices themselves can power off the red wire, but those are ones that consume little power.
Consider an appliance like an electric stove for example - the yellow wire is like the plug that you put in the socket. That is a permanent source of power.
But burner switch on the stove is the one that controls when it is really turned on and off. Until you turn on that switch, no significant power is drawn through the socket.
If your stove has a clock, then it will draw just a small amount of power from the socket irrespective of the switch.
That is why the yellow wire is sometimes called as the "memory" wire in electronics.
Loose connections are always known suspects - been there multiple times So make sure all connections have good contact.
You've tied together the HU Red and MOST Red with the HU blue/white wire => this is an issue.
Blue/White is an output from the HU and the HU Red wire is an input to the HU.
HU Red should be connected to the fat Red wire coming from your HVAC orange wire. Nothing else to be connected to this fat red wire.
HU blue/white should be connected to MOST Red wire. Nothing else should be connected to the MOST Red wire.
These are 2 different circuits. Do not combine them.
The yellows and the blacks look fine.
There is a difference between the yellow and red wires. The yellow wire is what supplies power to the HU and the MOST Box.
If you notice it will be much thicker than any of the red wires.
The red wire is just used as a switch - to signal devices to turn on and off. In some cases those devices themselves can power off the red wire, but those are ones that consume little power.
Consider an appliance like an electric stove for example - the yellow wire is like the plug that you put in the socket. That is a permanent source of power.
But burner switch on the stove is the one that controls when it is really turned on and off. Until you turn on that switch, no significant power is drawn through the socket.
If your stove has a clock, then it will draw just a small amount of power from the socket irrespective of the switch.
That is why the yellow wire is sometimes called as the "memory" wire in electronics.
Gotcha, thanks very much for the input!!
Back to revisions later this evening, and hopefully get everything sorted out soon!
Success! Well, sorta. The fibre optic connector on the MOST adaptor busted, so I had to go to another one I have (I ordered two, as I’ll soon be doing a CarPlay head unit install on my C55 AMG). Now the head unit turns on and off with the key.
However, I do notice the dreaded amplifier pop sound once ignition is off. I have thus ordered two PAC TR4 modules.
Question on wiring that though. It has four wires, 12v constant and ground I get. Then it has low voltage trigger input and 12v output.
low voltage trigger input should be connected to blue/white off the head unit, then the 12v output to the red MOST wire?
Success! Well, sorta. The fibre optic connector on the MOST adaptor busted, so I had to go to another one I have (I ordered two, as I’ll soon be doing a CarPlay head unit install on my C55 AMG). Now the head unit turns on and off with the key.
However, I do notice the dreaded amplifier pop sound once ignition is off. I have thus ordered two PAC TR4 modules.
Question on wiring that though. It has four wires, 12v constant and ground I get. Then it has low voltage trigger input and 12v output.
low voltage trigger input should be connected to blue/white off the head unit, then the 12v output to the red MOST wire? A
Yes, that sounds right. Blue/white goes as input to this module and it's output becomes the switched input for the most box.
That said.. this seems pretty expensive for a delay module (relay).
Yes, that sounds right. Blue/white goes as input to this module and it's output becomes the switched input for the most box.
That said.. this seems pretty expensive for a delay module (relay).
I found them on Amazon Canada for about C$35 each. The ones you pointed out in posts a couple years old were no longer available from Amazon US, and I couldn't find anything comparable on Amazon Canada unfortunately. I tried a local car audio shop, and told them what I wanted. The guy then asked me for make, model and year which was a bit confusing. Then said they needed C$700 for a whole harness, and they don't sell just the module. So that call ended pretty quickly...and Amazon Canada will get me the two PAC TR4 units tomorrow, so I should have it all wrapped up soon.
Meanwhile, AvinUSA says they will take the broken MOST adaptor back and replace with a new one so I'm happy with that too.
I found them on Amazon Canada for about C$35 each. The ones you pointed out in posts a couple years old were no longer available from Amazon US, and I couldn't find anything comparable on Amazon Canada unfortunately. I tried a local car audio shop, and told them what I wanted. The guy then asked me for make, model and year which was a bit confusing. Then said they needed C$700 for a whole harness, and they don't sell just the module. So that call ended pretty quickly...and Amazon Canada will get me the two PAC TR4 units tomorrow, so I should have it all wrapped up soon.
Meanwhile, AvinUSA says they will take the broken MOST adaptor back and replace with a new one so I'm happy with that too.
Thanks for your help throughout!
Don't mention it That's what these forums are for.
I didn't realize that you were in Canada all along.. Amazon options are quite limited there.
Quite a few US sellers might be willing to do shipping to CA - but time/cost will be more I guess.
So long as it solves the problem either works.
Oh man, this project seemingly will never end! The PAC TR4 unit came in, and I just tested it, but still get the amplifier pop when the key comes out. Dunno what else to do there.
And then disappointingly, the ebay sourced fascia surround and headunit pocket don’t fit too well either. Called up the local shop to order the Metra one instead. Went to pick it up and instead of sending the grey one I asked for, they sent a black one. Boo hiss.
Oh man, this project seemingly will never end! The PAC TR4 unit came in, and I just tested it, but still get the amplifier pop when the key comes out. Dunno what else to do there.
And then disappointingly, the ebay sourced fascia surround and headunit pocket don’t fit too well either. Called up the local shop to order the Metra one instead. Went to pick it up and instead of sending the grey one I asked for, they sent a black one. Boo hiss.
Hmm.. sorry that it's dragging on. My saga with retaining multifunction controls went on for months. At this point, you might as well try connecting the most box red wire to HU red wire and just seal the blue/white wire and see how that goes.
Hmm.. sorry that it's dragging on. My saga with retaining multifunction controls went on for months. At this point, you might as well try connecting the most box red wire to HU red wire and just seal the blue/white wire and see how that goes.
So doing that should turn on/off the amp (through the MOST unit) via accessory power instead of by the head unit. Guess there's nothing to lose.
Seems the PAC TR4 is only to rectify amplifier turn-ON pop, not turn-OFF pop. Also, it seems that the Stinger SGN21 is no longer available either. There are also options of the PAC TR7 and the Metra AX-MTR but those two seem quite complicated. Found them referenced in this article here: https://caraudioadvice.com/how-to-fi...-turn-off-pop/
A bit more Googling turn up these two products from Navone Engineering though:
I'm going to call them tomorrow to chat with them to see if either of those items will help. Dunno which one though.
I did manage to get the eBay sourced fascia to work though it's not as secure as I'd like. The Sony XAV-AX5000 I have is actually just single DIN behind the double DIN screen, so the fascia doesn't sit as securely in the cavity because only two of the four retaining prongs are connecting. That said, I'm quite happy to have Carplay finally!
Thanks for this DIY guide. Ordered the MOST decoder from Seicane and installed my Pioner DMH1500NEX over the weekend. Everything works perfectly and I don't get any noise or pops during shutdown.
ok, let's clear this up NAVTv and the other expensive MOST box kits also have a CANBus decoder module that takes more inputs and gives out more output signals. In my current setup I have the Connects2 kit which also has a steering wheel control module so I can keep my multifunction buttons. These kits that take in the CAN Hi and CAN Lo signals also know to emit a switched/accessory power output signal. This is what is sent to the HU in those kits as their switched/accessory input signal. And in this case, we won't need to tap an ignition-controlled accessory source from the fuse box.
Since you don't have a CANBus module, you have to get the switched/accessory signal from the fuse box - no idea where the white wire came into the picture here.
The blue/white coming off the HU is an amp-turn-on output signal. And this will go as the input signal to the MOST Box to turn on the amplifier.
So the blue/white wire from the HU needs to be connected to the Red wire of the MOST Box.
Acc/Ignition wire coming from the fuse box => Switched/Power signal to the HU
Blue/White wire from HU => Red wire in the MOST Box
shyamvenky I want to say thanks, this really helped me to get my new radio working. Didnt know I needed the parking brake bypass so I ordered that and will get that setup as well. I found that the mounting bracket was cheap and a POS, which one did you order? I am having a whine noise come through the speakers as well which sucks.
Hello everyone! First time poster! Just stopped to say that I also successfully installed an aftermarket radio with the "cheap MOST Box" -- thanks to OP and everyone's contribution!!!
However, while the audio works perfectly, I do vaguely remember that after connecting everything from the new aftermarket system side, 2 cables from the car side remain unconnected. I have a 987 w bose, no steering wheel buttons. Are these 2 unconnected cables "CANBus"? If so, what are the implications of not connecting them? Is there a risk? What functions did I lose by not connecting these 2 cables (my audio works perfectly)? Thanks!!!
shyamvenky I want to say thanks, this really helped me to get my new radio working. Didnt know I needed the parking brake bypass so I ordered that and will get that setup as well. I found that the mounting bracket was cheap and a POS, which one did you order? I am having a whine noise come through the speakers as well which sucks.
Glad that this thread is useful to more and more folks If you don't have a CanBus module, then you could tap into the parking brake wire by disassembling the center console - but a bypass is much quicker :P
I too used the cheap HU enclosure and it sucks! I gave huuuuuuge feedback to Metra who is one of the manufacturers of the cheap trim kit - but I guess they don't care.
I broke off 1 or 2 tabs to ensure that I can take the HU out if I need to. Their official manual says that you need to disassemble the dash to get the thing out
Now there is a more expensive metal bracket that I've used before on a previous 997 - that one is very good - Scosche I think. But this one was $10, so no-brainer :P
As for the whining noise - if it goes up and down with the engine revs, then it is known as "alternator whine" - most likely grounding issues or loose power connections
I too have it in my current state now, but am lazy to dig into the cubby and fix the wires - I'll get to it later in the summer maybe.
05-13-2020, 04:06 PM
So make sure all connections have good contact.
