# Any way to keep the HU from restarting when starting the car



## bird333 (May 28, 2008)

HU is Pioneer Avic N4. If I am already listening to the stereo with the car off, when I start the ignition the HU 'reboots'. Is there a way to stop that?


----------



## SaturnSL1 (Jun 27, 2011)

Run the head unit off a switch straight to the battery. Not really sure it's worth it.


----------



## minbari (Mar 3, 2011)

bird333 said:


> HU is Pioneer Avic N4. If I am already listening to the stereo with the car off, when I start the ignition the HU 'reboots'. Is there a way to stop that?


sure, just find a fuse that is not off when cranking and tap it for the HU. Then it wont shut off.

To be safe I would run a wire to the battery for power and just use the tapped fuse as a control for a relay though.


----------



## bird333 (May 28, 2008)

minbari said:


> sure, just find a fuse that is not off when cranking and tap it for the HU. Then it wont shut off.
> 
> To be safe I would run a wire to the battery for power and just use the tapped fuse as a control for a relay though.


I kinda like the relay idea but will the radio never turn off though?


----------



## jimboman (Jun 24, 2008)

Find an accessory lead near the ignition switch that is hot in start and run.


----------



## Victor_inox (Apr 27, 2012)

All valid suggestions unless reboot caused by voltage drop while cranking


----------



## [email protected] (Nov 7, 2010)

Could you use a capacitor on the switched power to the radio so that when it dropped during the key cycle the cap could float the voltage until it returneD?


----------



## minbari (Mar 3, 2011)

bird333 said:


> I kinda like the relay idea but will the radio never turn off though?


It will still turn off when the key is off. You dont want to tap a constant on fuse. You want one that is on in the run and crank key positions

sent from my phone using digital farts now Free


----------



## trumpet (Nov 14, 2010)

My Precision Power P771NX stayed on through engine cranking if it was booted up beforehand hand. I loved that feature. I assumed it has extra large capacitors inside to do that.


----------



## Justin Zazzi (May 28, 2012)

[email protected] said:


> Could you use a capacitor on the switched power to the radio so that when it dropped during the key cycle the cap could float the voltage until it returneD?


I use this method and it works great! I also added a diode so the cap cannot discharge backwards toward the car battery, but instead only discharges to keep the radio's switched voltage high enough to get the desired effect.


----------



## REGULARCAB (Sep 26, 2013)

I always ran my HU straight from the battery and also ran a switch to the "ignition" lead on the HU. Yeah it would reboot from voltage drop when i cranked it, which i never liked. I just got in the habit of switching it off before i turned the truck on. Doesnt much help with your problem but i have yet to find a work around, and if my HU rebooted due to voltage drop i cant imagine it was good for my amps either.


----------



## bird333 (May 28, 2008)

minbari said:


> It will still turn off when the key is off. You dont want to tap a constant on fuse. You want one that is on in the run and crank key positions
> 
> sent from my phone using digital farts now Free


I looked at the wiring diagram for my car. The radio is already hooked up to a source that is hot in those positions. I think I am going to have to use the capacitor solution.

EDIT: I was wrong. It's ACC and ON. But nothing is ACC, ON, and Start so I still want to do the capacitor trick.


----------



## bird333 (May 28, 2008)

Jazzi said:


> I use this method and it works great! I also added a diode so the cap cannot discharge backwards toward the car battery, but instead only discharges to keep the radio's switched voltage high enough to get the desired effect.


Do you have a parts list/schematic for this?


----------



## mooch91 (Apr 6, 2008)

Maybe some sort if time switch with relay on the ignition lead on head unit that holds it live for 15 seconds after the ignition is turned off?

Sent from my mobile device.


----------



## Justin Zazzi (May 28, 2012)

bird333 said:


> Do you have a parts list/schematic for this?


Here is what I built for my car. The capacitor charges when the car supplies voltage through the switched accessory wire (usually from the ignition) and the radio turns on like normal.

When the keys are removed, the door is opened, or the car is cranking to start the engine, the accessory wire usually goes low and turns the radio off. The capacitor will keep the accessory input to the radio high for a short time until is discharges, and the diode prevents the capacitor from discharging back towards the battery.

A larger capacitor will keep the radio on longer, and my radio will remain on for about 5 seconds with this setup and a 2,220 uF (microfarad) capacitor (plenty of time to cank the engine). Choose a capacitor somewhere around this value to start, and make sure it is rated for at least 16 volts (higher is ok but not required).


----------



## Justin Zazzi (May 28, 2012)

The above trick only works if your car (for whatever reason) is not able to keep the _ignition wire_ going to the radio with a high enough voltage.

If the voltage to the radio _through the constant +12v lead_ is dropping low enough to cause the radio to reboot, you need something a little more sophisticated.


----------



## bird333 (May 28, 2008)

Jazzi said:


> The above trick only works if your car (for whatever reason) is not able to keep the _ignition wire_ going to the radio with a high enough voltage.
> 
> If the voltage to the radio _through the constant +12v lead_ is dropping low enough to cause the radio to reboot, you need something a little more sophisticated.


Thanks for the drawing. When the key is in the start position, power is completely cut from the radio. I think this will work fine. A couple of questions.

1. What diode do I need?
2. Does the cap have to be connected to the ground coming from the radio or can it be any chassis ground? Sorry if this is a dumb question as I think they should all be the same but I am just double checking.

Thanks!


----------



## minbari (Mar 3, 2011)

Any power diode with enough current capacity will work. Not small signal or zener.

Yes any ground will work 

sent from my phone using digital farts now Free


----------



## D-Bass (Apr 27, 2012)

what you need is an ignition wire, not an accesory wire. ignitions are always hot when the key is in the on and start positions. accesories drop out upon start on most vehicles(german vehicles often don't)


----------



## whitrzac (Jul 30, 2013)

Jazzi said:


> Here is what I built for my car. The capacitor charges when the car supplies voltage through the switched accessory wire (usually from the ignition) and the radio turns on like normal.
> 
> When the keys are removed, the door is opened, or the car is cranking to start the engine, the accessory wire usually goes low and turns the radio off. The capacitor will keep the accessory input to the radio high for a short time until is discharges, and the diode prevents the capacitor from discharging back towards the battery.
> 
> A larger capacitor will keep the radio on longer, and my radio will remain on for about 5 seconds with this setup and a 2,220 uF (microfarad) capacitor (plenty of time to cank the engine). Choose a capacitor somewhere around this value to start, and make sure it is rated for at least 16 volts (higher is ok but not required).


I did this to my 80prs yesterday.

The cap I used was a little big

10,000uf is good for ~30seconds:laugh:


----------



## s3john (Mar 12, 2014)

Thank you for taking the time last fall to share your diagram. I have a pioneer avh-x2600bt and really hated it rebooting when I started my truck. Your fix worked a charm. Thanks!! 




Jazzi said:


> Here is what I built for my car. The capacitor charges when the car supplies voltage through the switched accessory wire (usually from the ignition) and the radio turns on like normal.
> 
> When the keys are removed, the door is opened, or the car is cranking to start the engine, the accessory wire usually goes low and turns the radio off. The capacitor will keep the accessory input to the radio high for a short time until is discharges, and the diode prevents the capacitor from discharging back towards the battery.
> 
> A larger capacitor will keep the radio on longer, and my radio will remain on for about 5 seconds with this setup and a 2,220 uF (microfarad) capacitor (plenty of time to cank the engine). Choose a capacitor somewhere around this value to start, and make sure it is rated for at least 16 volts (higher is ok but not required).


----------



## 1fastkingcab (Nov 23, 2010)

That seams like a lot of work, all you need is to have your switched power (red) to the radio run off of a fuse that is hot with the key on and while cranking, I have used the EFI circuit to trigger a relay that turned on my stereos in the past.


----------

