Hi there

the head unit in my car stays on for about 30 seconds after the car is turned off, so i've pulled it all out today to have a bit of a poke around

when i stick a multimeter in the ACC connection (the red/blue wire), it comes on to 12V instantly when the key is turned on, but when turned off instead of dropping to 0V, it takes about 5-10mins. does this mean there is a bad earth or something elsewhere in the system?

thanks!

You done a current draw test?

This should help (http://flashoffroad.com/electrical/Batteries/BatteryDrain.html)

With the VE Commos and BMWs for instance you need to wait a certain amount of time before the car "goes to sleep" so to speak - for control units and modules to shut down completely.

I don't think this is the case for our cars but I can't say to be certain. Are you having any problems starting your car?

My headunit also stays on for 30 secs. I used to havce one that beeps. I guess its something about finnishing off the electricity in the line i dunno...lol

Depending on the device it's not unusual at all for there to be 'residual' voltage after the cut of power supply. Pretty nearly all electrical devices will have at least some capacitors in their circuitry, and depending on the device and application some of those capacitors will be quite large.

Capacitors work by storing up charge and then releasing it as required. Just because you turn off the power supply doesn't mean the charge (which is measured as a voltage) is automatically and instantaneously dissipated - it takes time. This is why there are prominent warnings on large devices such as televisions not to pull them apart and tinker with the insides, due to the risk of electrocution posed by capacitors which may still hold substantial charges despite the device not being plugged in or drawing power.

Besides anything else, the only thing that really needs to concern you is when electrical devices are drawing *current* after they've been switched off. Grab a high school electronics book, or any of the available magazines at your local newsagent, and they'll be able to explain it all for you in more detail.

yeahh mine stays on for about 30 seconds too.. never had a problem starting it or any power issuses so i just leave it.. cant be bothered poking around..

if i have some kinda other powerdraw, such as something plugged into the lighter socket, or the wipers on it will turn the mucic off as soon as i turn the car off too..

Hi there

the head unit in my car stays on for about 30 seconds after the car is turned off, so i've pulled it all out today to have a bit of a poke around

when i stick a multimeter in the ACC connection (the red/blue wire), it comes on to 12V instantly when the key is turned on, but when turned off instead of dropping to 0V, it takes about 5-10mins. does this mean there is a bad earth or something elsewhere in the system?

thanks!

What model do you have? Exec's will be just a straight ACC line, no caps in the system, but if you have ETACS it might have something to do with it
yann89 - no lol it doesnt drain off, once you disconnect power it will stop, unless there is a cap.

thanks for the replies! its an ei verada.

i thought it may just have been a big decoupling capacitor or something, but it seems weird because i couldnt see any mention of one in the circuit diagrams. but the rest of the car works not too badly so maybe i should stop fiddling....

OEM HU's are connected to both "constant/unswitched" 12v and "accessory/switched" 12v , and I presume that a Verada ei has a power antenna that takes a little while to retract after car key has been turned-off? Would that have something to do with it?

Totally unrelated: Mum n dad's TJ Exec has a single-CD radio HU with a "key-out 1-hour radio power" feature - we love it. Can work on the car or sit in a car park with stereo going without needing key switched on. Wish some of the fancier HU's had the same idea - think its a Eurovox set, whereas my KJ has a Misubishi Electric Japan HU.

it's just the kind of headunit, i've been through 6 different headunits and have found that the newer ones stay on for 30-45 seconds. but when i leave the lights, blinkers, wipers, etc on the headunit turns off straight away. like a stored power source.

It's a KR verada...... not sure if they have the same ETACS system as the KS, but I know in mine it will leave the interior lights on for a few seconds then fade them out.

It will also leave power to the electric windows so you can wind them up. This lasts about 30 seconds.

You sure you are tapped into the right circuit?

This might sound silly .. but you don't have one of those big ass caps in your sound system / on your subs do you?

;1058732']
yann89 - no lol it doesnt drain off, once you disconnect power it will stop, unless there is a cap.

so the headunit i look at every day which stays on for 10secs after the ignition is turned off isnt right?

Some H/U's beep. Ive noticed alot of sony units do it...

so the headunit i look at every day which stays on for 10secs after the ignition is turned off isnt right?

Some H/U's beep. Ive noticed alot of sony units do it...

Internal capacitor in the HU dude

;1063887']Internal capacitor in the HU dude

...so was i so wrong in that the HU drains the energy inside itself before it turns itself off?

The HU would have an internal ca which would discharge slowly (I'm guessing) ACC will turn off when wel, your not on ACC....so how power is still coming out of it is beyond me. but yes hu would drain the energy inside itself but nothing to do with the acc line

;1063898']The HU would have an internal ca which would discharge slowly (I'm guessing) ACC will turn off when wel, your not on ACC....so how power is still coming out of it is beyond me. but yes hu would drain the energy inside itself but nothing to do with the acc line

spot on,why dont you grab a multi meter or a test light and probe the accesory circuit while toggling the ignition switch,the only way i could see this happening is if a 12V switched supply was pinched from something using the "BCM" or mits equivalent (interior light,power window supply etc) ouputs that leaves a supply on after the car is turned off

either that or read the CD players instrution book!

Steve

Yeh the other day I accidentally connected my constant ON to my illumination switched on on my head unit .. causing the dash lights to light up.

It's entirely possible someone wired a deck incorrectly or something (or some other accessory)

spot on,why dont you grab a multi meter or a test light and probe the accesory circuit while toggling the ignition switch,the only way i could see this happening is if a 12V switched supply was pinched from something using the "BCM" or mits equivalent (interior light,power window supply etc) ouputs that leaves a supply on after the car is turned off

either that or read the CD players instrution book!

Steve
Wel he said he has ETACS so i'd guess it'd have to do with the ETACS system itself?
Bleh who knows...