TheSamba.com :: View topic - stereo wiring

Thu Dec 16, 2021 9:47 pm

I'm swapping out an aftermarket head unit for a different aftermarket head unit. The original vanagon wiring plugs are still intact. Comparing pig tails of the two different aftermarket stereos to see if the new head unit was essentially plug-n-play, everything aligns except for ignition and constant power wires.

What is the effect of combining these two and wiring them to the A7 pin of the factory wiring plug (like the outgoing stereo)? Does that allow the stereo to power on with ignition off? Is the drawback that it's a parasitic drain on the battery even when off?

Thu Dec 16, 2021 10:26 pm

Constant power is to keep the presets on the radio, ignition power is for all radio functions. You can tie them together which will make the radio functional even with the ignition off.
Once you kill the battery and get stuck somewhere by accidentally leaving the radio on you will probably want to change to a on/on toggle switch to keep that feature or just wire it like it should be.

Thu Dec 16, 2021 10:43 pm

Here's a how-to for wiring the stereo to power-on when the key is put into the ignition. I don't mean the "key-on" position on the ignition. When wired correctly, just putting the key in the ignition will power up the stereo.

http://www.weidefamily.net/vanagon/HTML/04/09/01.html

Fri Dec 17, 2021 7:01 am

This is a common problem that we also went through when we replaced the cheap Walmart stereo that the previous owner had installed with a mechless Blaupunkt stereo.

Our experience was that even with turning the stereo off, the backlighting never completely turned off creating a parasitic drain on the battery that resulted in a dead battery if our van sat for more than two days.

I chose to install a "kill switch" on the main power feed to the stereo. This way the memory is still maintained but the backlighting can be switched off when the stereo is not in use. This setup also allows you to turn the stereo on without having the key in the ignition.

By the way, an advantage to installing a mechless stereo is that the chassis is shallow enough that you can slide it all of the way into the dash without modifying the rear radio support that is inside the dash.

Fri Dec 17, 2021 8:06 am

izzydog wrote: Here's a how-to for wiring the stereo to power-on when the key is put into the ignition. I don't mean the "key-on" position on the ignition. When wired correctly, just putting the key in the ignition will power up the stereo.

http://www.weidefamily.net/vanagon/HTML/04/09/01.html

This is far and away the best way to wire up a radio in any 80s-90s VW. (Plus at least some late 70s, such as my '78 Bus.)

Though with most if not all radios, the key in wire is simply a signal to turn on wire; all the power to run the radio comes through the constant wire. So the relay isn't strictly necessary.

On one or two VWs I've owned, I've even just crimped a small spade onto the key on wire from the radio, and plugged it into the appropriate slot where the door buzzer once had been.

But if there is any doubt, there isn't really a reason to not use the relay.

Fri Dec 17, 2021 10:28 am

I believe the original factory harness for the radio had a single constant power lead. This was fine with older head units that had a simple an off-on switch. Modern head units have both switched and constant power wires in the harness. To prevent parasitic drain you must wire these separately to appropriate sources. We installed a new Blaupunkt head unit with a removable faceplate which also solves the issue.

Fri Dec 17, 2021 10:32 am

For my stereo and gps spedo i tied into the large igniton wire on the column. works great for shutting off accessories whe the key is off.

Fri Dec 17, 2021 10:41 am

jb20thae wrote: I'm swapping out an aftermarket head unit for a different aftermarket head unit. .... Is the drawback that it's a parasitic drain on the battery even when off?

Some thoughts:

- does manual spec maintenance current draw?

- can stereo basic settings be configured easily without looking at display?

- if stereo connects to an aux battery, compare battery size, type, duration - amount of maintenance current draw vs reconfiguration hassle and possible distraction while driving due to stereo configuration.

- an aux battery often suffers worse wear and tear via poor, no charging, hard use etc.

- if head unit requires security code does removing all power require code reset?

Neil.

Fri Dec 17, 2021 12:07 pm

Thanks all. It looks like the head unit (Continental) has a logic function where Logic On limits the use to 1hr when ignition is off, and Logic Off prevents the head unit from turning on when the ignition is off.

With that said, would I still wire ignition and constant from head unit to A7?

Fri Dec 17, 2021 1:15 pm

jb20thae wrote: Thanks all. It looks like the head unit (Continental) has a logic function where Logic On limits the use to 1hr when ignition is off, and Logic Off prevents the head unit from turning on when the ignition is off.

With that said, would I still wire ignition and constant from head unit to A7?

I feel like your unit will need the ignition wired to something different than the constant on for it to be able to work as you're describing.

So you'll still want to wire them separately.

Sounds like this is a function similar to radios in my '02 Golf and '05 Passat--the key turns it on and off as normal. But you can hit the power button with key off and the radio will turn back on and stay on for some longish duration. (Maybe an hour) without the key.

Fri Dec 17, 2021 1:54 pm

vwwestyman wrote: jb20thae wrote: Thanks all. It looks like the head unit (Continental) has a logic function where Logic On limits the use to 1hr when ignition is off, and Logic Off prevents the head unit from turning on when the ignition is off.

With that said, would I still wire ignition and constant from head unit to A7?

I feel like your unit will need the ignition wired to something different than the constant on for it to be able to work as you're describing.

So you'll still want to wire them separately.

Sounds like this is a function similar to radios in my '02 Golf and '05 Passat--the key turns it on and off as normal. But you can hit the power button with key off and the radio will turn back on and stay on for some longish duration. (Maybe an hour) without the key.

Wiring separately would mean running new wire to the ignition due to factory wiring only having constant, ground, and dimmer?

Fri Dec 17, 2021 2:04 pm

jb20thae wrote: vwwestyman wrote: jb20thae wrote: Thanks all. It looks like the head unit (Continental) has a logic function where Logic On limits the use to 1hr when ignition is off, and Logic Off prevents the head unit from turning on when the ignition is off.

With that said, would I still wire ignition and constant from head unit to A7?

I feel like your unit will need the ignition wired to something different than the constant on for it to be able to work as you're describing.

So you'll still want to wire them separately.

Sounds like this is a function similar to radios in my '02 Golf and '05 Passat--the key turns it on and off as normal. But you can hit the power button with key off and the radio will turn back on and stay on for some longish duration. (Maybe an hour) without the key.

Wiring separately would mean running new wire to the ignition due to factory wiring only having constant, ground, and dimmer?

Yes.

Just wire it up as suggested earlier in the thread. That is really the only way to make the stereo work properly.

As I said before, if you're not using your door buzzer, you can literally plug the wire into the empty slot for the relay that the ignition switch signal goes to. Otherwise tie into the grey/blue wire on the back side of the relay or by the ignition switch. Find the correct slot with your multimeter. It'll be the one that has 12v going to it when the key is in the ignition and doesn't when the key is removed. (No need to turn the key to on/run.)

Its pretty clear that your stereo is only using the ignition wire as a "turn on" signal. It won't be pulling much power through that wire.

Fri Dec 17, 2021 2:19 pm

Great, thanks. Final question: if I just wire the constant and utilize the "logic" function of the radio, would there still be battery drain once the auto-off logic kicks in?

Fri Dec 17, 2021 10:16 pm

Hard to say what will happen if you don't wire it as the radio manufacturer recommends.

My guess is you would have to hit the power on button to turn it on any time, and power off after an hour or whatever. And you'd have to hit the power button to turn it off if you wanted it to go off earlier.

Essentially, it sounds like it would assume you had never ever put a key in the ignition. Because it would have no way of knowing you did.

By contrast, if you wired both to constant power, it would think that the Van is turned on all the time.

But that is just guesses with this "logic" funciton.

Not trying to be rude here, but I am struggling to understand why you seem resistant to just wiring it up as we've recommended?

Fri Dec 17, 2021 11:02 pm

There is switched power available from the back of the fuse box in the G section. I don't like the key in ignition approach myself(tried it for a short while) I use a different method to power up the head unit if I ever want to while parked. Giving the head unit both constant and keyed power that it is wired for is quite easy and I seen no reason not to.

Sat Dec 18, 2021 9:43 am

Wiring both head unit leads to constant power in the factory harness allows you to maintain presets and use the radio with the ignition off (or key in the ignition) when camping, tailgating, wrenching, etc. This is my preferred configuration.

Sat Dec 18, 2021 10:34 am

The presets need to go to a 30 source. I wired the stereo power to the center position of an on-off-on toggle. 30 went to one end and 15 to the other, so I can have the radio on with ignition off or on when driving, but have it automatically turn off when I stop to prevent a drain. It's possible to have the volume on so low you don't know it was left on. Automaticity is where it's at these days.

Having the center off, keeps lights on the head unit from being on while night driving if I don't want the radio on.

Duncan

Sat Dec 18, 2021 3:54 pm

Perfect, thanks guys.