Parking brake override for a Clarion NX501?

[jemenake]

First off, I know "that kind of thing is dangerous and illegal" and that my teeth will probably fall out and I'll lose all of my friends. I'm not looking for legal or life guidance; I'm looking for electrical advice.

Now, with that out of the way, I'm looking to defeat the parking brake override on a Clarion NX501.

On my old head-unit, I was able to just tie the parking-brake wire to ground. The Clarion is a little more clever, though. Temporarily, I've got it wired to a switch, so I can toggle the switch a few times and it will eventually give me the video on the screen.

The goal is to have it all happen magically, behind the dash. No futzing with switches mounted on the dash or whatnot. I'm able to construct a circuit which can do anything I want with the parking-brake wire, but I'm having trouble deducing exactly what to do to unlock it.

I've tried using a relay to ground the wire when the ignition is turned on, but that didn't seem to do the trick. I've experimented with delaying the grounding for a few seconds and that seemed to work once, and then I think it failed the last time I tried it.

Has anybody figured out a circuit which reliably defeats the parking-brake lockout on these new-fangled head units?

[Bird76Mojo]

I'd like to have an answer to this as well. I see from the manual that it says to connect the parking brake wire to the negative on the parking brake indicator bulb. So the headunit must be looking for voltage, as any electricity that the bulb isn't using, would be shunted to ground through the negative wire. Am I incorrect here?


GB

[winkychevelle]

simple ground relay triggered by the headunits amp remote wire should work. triggering of of th ignition wire doesnt give the unit any time to boot up and u are essentially just grounding it 24/7 since the deck is seeing it as grounded upon bootup. the remote wire give u a period of delay that should allow the unit to display video.

legal disclaimer: i personally do not recommend this for any car that is used upon a legal road way as it is an illegal modification to the vehicle and can result in a driver distraction that could cause the driver to lose control of said vehicle and cause a crash.

[jemenake]

simple ground relay triggered by the headunits amp remote wire should work.

Well, that doesn't work, either, these days. The units want to see a longer delay, apparently.

[jemenake]

I'd like to have an answer to this as well.

What I ended up doing was I just bought a parking brake bypass module on eBay for $20. I just searched for "clarion brake bypass" and found at least two different guys selling little three-wire modules for $20+s/h. It was guaranteed to work, so I figured I had nothing to lose. Wired it to amp-turn on, parking wire, and ground and, boo-ya, problem is solved. Based upon how much I had already dropped on the head unit, back-up camera, Sirius unit, etc., $20 was nothing... and it's a lot less than what it was costing me in my time to create my own solution.

[bubbagumper6]

What I ended up doing was I just bought a parking brake bypass module on eBay for $20. I just searched for "clarion brake bypass" and found at least two different guys selling little three-wire modules for $20+s/h. It was guaranteed to work, so I figured I had nothing to lose. Wired it to amp-turn on, parking wire, and ground and, boo-ya, problem is solved. Based upon how much I had already dropped on the head unit, back-up camera, Sirius unit, etc., $20 was nothing... and it's a lot less than what it was costing me in my time to create my own solution.

Pop it open and post some gut pics...might help someone recreate it later

[buzzy1981]

Its simple just wire your parking brake wire and reverse wire together and it creates a ground loop and works

[johnpcunningham]

Ok, being an electrical engineer I finally broke this one down.

When the Clarion radio is first turned on, it "looks" to see if the parking brake wire on the radio is already tied to ground. If it is, video will not play. What it wants is to see the wire floating (not connected to anything, or to 12 volts) when the radio is turned on, and then go to ground afterwards. In the Clarion manual you will find a paragraph that talks about "If the video wont play, disengage the parking brake and then re-engage it again"

I have a Jenson DVD player in another car and tying the parking brake wire directly to ground works just fine, just not on the Clarion.

For the Clarion radios to work properly, this is what should happen:
1) Power radio on. Parking brake wire should be floating - tied to a high-Z input like an MCU pin or the Drain of a FET
2) After some period of time (2 to 4 seconds), the parking brake wire on the radio should be brought to ground. This will allow video play without having a connection to the parking brake.


So how do you fix this?

1) A simple way would be to use a basic toggle switch. Tie one side to ground and one to the parking brake wire on the radio. Power the radio on and the toggle the switch leaving it in the connected position (switch inputs shorted).
2) Use a simple FET or NPN transistor with a long RC circuit on the gate or base. Tie the Drain or Collector to the parking wire on the radio, the Source or emitter to ground. On the gate or base, use a long time RC circuit. Allow 2 to 4 seconds of time before the charge turns on the FET or NPN and effectively ties the parking wire to ground. The voltage input should be the AMPLIFIER TURN ON power line from the radio, not tied directly to VCC.
3) Use a cheap Microchip or Atmel microcontroller. After some delay, the MCU will turn on an external FET that will effectively ground the parking brake line on the radio. Once again, use the AMP power on wire from the radio (on mine it is the blue wire) as the power to the MCU circuit. You will also need a voltage regulator to bring the 12V down to 5.o or 3.3V, depending on which MCU you use.
4) Seems some folks on EBAY are selling circuits that do this as well for ~$20

Hope this helps