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Brake Pedal Turns Radio On.


GrandpaSquid

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The other day I noticed that with no key in the ignition pressing the brake pedal cut the radio on. Truck is 93 Ranger 4.0 Auto. I used all the factory wires when installing the upgraded sound system. I used one of those plug and play wiring adaptors for the head unit, as well as premade connectors to the cabin speakers so none of the factory loom is cut. There are two 8" subs powered by one amp while the four cabin speakers are run off another amp. The ignition is a little wonky the lock ring(silver part with the wings) spins and the key warning chime will go off if you knock it to the wrong position. Been like that since I bought the truck, radio has only started a few days ago. I attached a video, don't really expect to get a solution just thought it was funny, but help is appreciated.
 


Josh B

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I thought it sounded funny too until I got here.
Wiring was the first thing they liked to put me on at Penske, and the last place I liked to be. It's much simpler there though, I really don't know how to tell you where to start, maybe somebody will though.
My best guess is to take a good long look at it and attempt to reverse engineer what they have done.
Maybe, if you reach a point where something seems to start working, take another long look at where you are and begin going back together with it in the direction you wish it to be in
 

RobbieD

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I know that it's not helpful, but the radio turning on with ignition key off and pressing the brake pedal, just doesn't make any sense.

1) When you say " with no key in the ignition pressing the brake pedal cut the radio on ", does the radio have sound output, just light up, or both?
2) Does the radio have to be turned "on" for this to happen? (i.e.- if the radio itself is off, it won't turn on with key off and brake on)
3) Does the radio have a remote turn on input wire?

Besides scratching my head, the only thing that comes to mind is that it's on the radio side, versus on the truck side.

I would go over, and check, all of the grounds of your sound system. Also check the original ground points in the truck. Shaky grounds can make for some incredibly crazy problems.

I could see a short between the radio power and brake light circuits possibly causing something like his, but those two circuits are well seperated in the factory wiring runs. Getting them crossed and shorted together would not be likely, unless the wiring has been "repaired" (or "improved upon") in the past. Besides, it would also light you brake lights with the key on, so like I say, very unlikely that this is what you have going on.
 

GrandpaSquid

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Key out of ignition in the off position. No power to windows or radio(pressing the power button), but as soon as the brake light switch is engaged(brake lights on) the radio powers up as if the key is on(run position). None of the factory wires have been cut, all factory connectors are intact and this only started recently. Set up has been in truck and working for a few months. It doesn't seem to effect anything, just kinda funny party trick.
 

Bill

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The stereo has a wire to disable the ability to access features if the parking brake is not set. You probably have it wired incorrectly.
 

GrandpaSquid

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The only thre wires used on my radio are power, ground, amd remote. It's the cheapest dual from Walmart. The rca outs go to the amps. And speaker wire is run from the 4 channel amp to the adapter pigtail. And this is a recent issue, stereo has be installed for a couple months with no issue.

* the bike has to be held to keep radio power when key off.


Update. I just found out while cleaning that the ON button for the cruise control also turns the radio on.
 

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The only thre wires used on my radio are power, ground, amd remote. It's the cheapest dual from Walmart. The rca outs go to the amps. And speaker wire is run from the 4 channel amp to the adapter pigtail. And this is a recent issue, stereo has be installed for a couple months with no issue.

* the bike has to be held to keep radio power when key off.


Update. I just found out while cleaning that the ON button for the cruise control also turns the radio on.
As far back as there have been digital displays in car stereos there have been at least four wires in use. There should be an accessory wire in addition to the three you mentioned. The standard color is red. This wire is connected to the ignition key and the ACC (accessory) circuit that allows you to listen to the radio without running the engine. If for some reason this wire is receiving 12V when turning on the cruise control or pressing the brake pedal it will make the radio turn on. The yellow wire is for the radio's memory. It is always at 12V.

Assuming it is the Dual XD18BT, see page 3 of the manual:
 

GrandpaSquid

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You are correct, that was an error on my part when writing this up. Those four wires are wired up using the adapter pigtail.

I unplugged the brake light switch to test. With switch unplugged the radio does not turn on, but the cruise ON switch still does. Also checked the around the pedal arm for possible pinched wires. Nothing touching, frayed, pinched, or dangling.

I did not want to take the steering wheel apart, but cruise still works fine as well. This album has some photos of the install.


 

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Do the brake lights turn on when you operate the cruise control switch?
 

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You are correct, that was an error on my part when writing this up. Those four wires are wired up using the adapter pigtail.

I unplugged the brake light switch to test. With switch unplugged the radio does not turn on, but the cruise ON switch still does. Also checked the around the pedal arm for possible pinched wires. Nothing touching, frayed, pinched, or dangling.

I did not want to take the steering wheel apart, but cruise still works fine as well. This album has some photos of the install.
I would double-check the wiring at the stereo to make sure something isn't crossed. Although, I don't know how something could get crossed and have the brake light or cruise control turn the radio on unless one of the "unused" pins connects those circuits, which is unlikely.

I've read about the multifunction switches causing bizzare problems and I do know the brake light circuit goes through the switch in some of Ford's vehicles. I wouldn't think anything from the multifunction switch goes to the radio harness, but car manufacturers have been know to do stranger things. So, the might be worth a check. I would think you could simply unplug the harness from the switch to see if the problem goes away. And at this point I think studying the wiring diagram to seek out where the brake light and cruise control circuits may be completing a connection to the power wire in the radio harness. If you have a local library card you should check and see if your local library has Chilton's Online so you can access the wiring diagram.
 

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So both the cruise control switch and the brake light switch are backfeeding power into the keyed 12v circuit... Interesting.

For what it's worth, I've got a similar issue on my '99 - if my headlights are on (in both the parking light and the headlight position), the accessory circuit on the truck is energized regardless of key position. So I can bump the lights on and immediately use the windows, turn on the radio, etc.

In my case, I think this started when I made a wiring adjustment during the V8 swap so that the new mechanical transfer case could control the 4wd shift position lights on the instrument cluster. But I'm at a loss as to what's causing it in your situation.

@RonD ought to be back on the forums any day and might have some input here.
 

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