Seems like most head units use a negative ground on the head unit for the parking brake trigger but mine needs a positive wire trigger. Scoured threads on head units but not finding the answer to my question for the 97. Thanks in advance!
Head unit parking brake positive wire trigger location (13 Viewers)
- Thread starter thetoyotaman
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Out of curiosity, why would a head unit unit need to know that the parking brake was applied (or not)?
Yeah, the 80 has a ground switch on the e-brake. Worst case, you could do it with a relay. Feed the relay with key switched 12+ to one side of both the coil (pin 85) and switch (pin 30) of the relay, splice the other side of the relay coil (pin 86) in with the wire feeding the e-brake swtich so that it gets ground when activated, now the normally open contact (pin 87) for your relay has 12v+ when you pull the brake.
I'm with @Irish Reiver though... what the hell does it care if you're parked? The only thing I could see that being for, is if it disables certain functions when you're driving, which would annoy the crap out of me.
COS80
SILVER Star
To lock you out of satnav, and such, while you're moving.
Sounds like flawed logic. 
COS80
SILVER Star
I'm sure it's a feature the government demands. You just permanently wire it and forget it even exists. So @thetoyotaman if you need a positive trigger, just wire it to the radio hot.Sounds like flawed logic.
the main reason is so you cant watch movies on the screen whilst driving, i just 'hot wired' mine to keep the kids happy!
Easier wiring and less irritation.
- Thread starter
- #9
A lot of the newer units have a smart logic that won’t allow you to straight wire a negative trigger to ground. They have a smart logic that needs to see the parking brake working. So, I’m wanting to find the positive side of the circuit without adding more stuff like a relay if possible to avoid issues. But yes, it’s required for satnav, settings, etc
That would be enough to get me to return it!
The wiring diagram is available in the resource section, but I'll save you some trouble: the hot side of the circuit is hot all the time, the switch is on the ground. You need a relay to get a hot wire that switches.
- Thread starter
- #11
So, you're saying the wire going in to the switch is hot? Because I put my multimeter on it and couldn't get 12 volts. I can check again. The brake light does light up on the dash.
I mean... Download the wiring diagram and look for yourself. Pretty much all of the gauge cluster has a common 12v source. It feeds the BRAKE dash light, then has two possible grounds: the e-brake switch and the warning sensor for low fluid.
