I have ordered a replacement head unit, Pioneer AVH-X7500BT, that has a detector for the parking brake. I want to install it with a tap into the regular parking brake AND a fake parking brake that I can activate with a simple switch to ground. I think I need a diode in the wiring setup but how do I wire it in so that I can optionally fool the stereo to think that the parking brake is on, for video playback but not confuse the car to think that the parking brake is on.

Goal - car always correctly understands if the real parking brake is engaged but not the fake-out switch. Radio head-unit correctly detects if the parking brake is engaged OR if a secondary switch to ground is engaged.

 

This is so you can watch a video as you drive? Hm-mm!

 

I have my wire just hooked up to a ground and I just watch video whenever I want, parking brake never comes into play. It's a lot easier since it requires less time and wiring.

 

This is an electrical engineering exercise without consideration for real world applications.

 

..............

Anyway, yes, it would require a diode. The switch will control a ground. The diode will go between the output of the switch and the actual parking brake output. The wire to the HU needs to be tapped above the diode. Make sure the mark is closest to the output to HU wire so the signal gets through.

Pretty easy to do, but even easier to do like Selbyl suggested and wire it to a ground. Only problem that may pop up is if that unit has navigation built in and you intend to use it. If it sees vehicle movement with the parking brake on, it knows something is fishy and will probably give you an on screen message that will annoy the crap out of you. Easy way around this is to just wire in a switch to that input wire. Flip it off when you know you wont be using video, flip it when you want video.

 

Before shows the basic parking brake which is a switch to ground when the parking brake is engaged.
After shows the modification to add a DIODE, in my case an LED (Light Emitting Diode) to allow current from the parking brake sensor in the head unit to flow through the actual parking brake. And a secondary path through a switch that will allow a simple SPTS (Single Pole Single Throw) to allow the radio to detect a ground / parking brake when the real parking brake is NOT set. The diode prevents the switched ground signal to be isolated to the radio head unit but not affect the car.
The switch is not shown in the real-life picture but closes the circuit between the green parking brake sensor/red LED lead and the gray wire to ground.
When the real parking brake is set, the LED will light as it provides a path to ground. When the fake switch is closed, it will NOT light.
The diode part of the LED blocks the signal from the car from flowing through the secondary switch.
Before.png

After.png

17ParkingBrakeLED.JPG

 

I don't understand why you are going through all the wiring trouble. Can't you just wire the head unit wire to one side of the switch, and the other to ground? If you are going to 'fake' it out, why just some of the time and not all the time?

James

 

The switch cannot be constant for this head unit. The DVD player wants to detect a GND then an open then another GND before it will activate. I like the option to activate the GND signal with the real parking brake, like you should. And only selectively activate the secondary switch as required.

 

Yes wouldn't it be easier and cheaper to buy a portable DVD player instead of all this trouble?
Besides you would not be tempted to watch and drive as much.

 

I've not heard of Pioneer doing this but I think Alpine has been doing it for a long time. There are specific bypasses for this.. it may or may not work with a Pioneer unit, I would do more research.

I'm sure this is overpriced for the parts included, but it is not a bad price. I would rather just pay the $$ than figure out what is needed and try to rig up something myself. Here it just a place to start: