Aerial/Antenna power source?

[murkey]

Hey all hope you can help..

 

On my Skoda Octavia MKII the antenna/aerial is powered, after taking the antenna base off yesterday I seen the head unit shut down as I foolishly didn't unplug it while unscrewing the 22mm nut, I must have sent a short through the system, now, the 12v powered antenna cable in the back of the head unit has no power and the HU will not switch on.

 

So does anybody know where the power for the amplified antenna resides as in fuse box, inline fuse somewhere, or if I shorted out the antenna base would that cut power to the cable?

 

I know its not the radio fuse in the engine bay box, or the 10a in the back of the HU plus I tried another HU to check I didn't blow my Bolero

 

Very frustrating so any advice very welcome 

Edited 13 June, 2021 by murkey

[langers2k]

The antenna uses 'phantom power'.

 

That means the headunit is applying power to the same wire that the antenna is using to provide the radio signal.

 

If the headunit isn't turning on and you're sure it's getting 12v, then there is a chance you've damaged something in the headunit...

[murkey]

2 minutes ago, langers2k said:

The antenna uses 'phantom power'.

 

That means the headunit is applying power to the same wire that the antenna is using to provide the radio signal.

 

If the headunit isn't turning on and you're sure it's getting 12v, then there is a chance you've damaged something in the headunit...

 

Thanks for the reply, the thing is I tried the old Stream that I took out for the Bolero which I know works and that is completely dead too, this makes me think that there is something between the head unit and aerial that has blown/shorted.

 

I do need to check the head unit is getting 12v, if that isn't the case and the fuse is okay what could be the problem - Can Bus?

[langers2k]

Oh, sorry, I misunderstood. I read it that the old headunit still worked when you refitted it.

 

If neither are working, then it's likely you've popped a fuse somewhere...

 

To start with, use a multimeter to check you've got 12v and ground on the quadlock connector in the car. The two circled in red should be power, the one circled in blue should be ground:

 

I would then only connect the quadlock and see if either headunit will powerup using the button as that should work regardless of if the CAN-bus side is working

[murkey]

Thanks Langers, will give that a go now and report back..

[murkey]

2 hours ago, langers2k said:

Oh, sorry, I misunderstood. I read it that the old headunit still worked when you refitted it.

 

If neither are working, then it's likely you've popped a fuse somewhere...

 

To start with, use a multimeter to check you've got 12v and ground on the quadlock connector in the car. The two circled in red should be power, the one circled in blue should be ground:

 

I would then only connect the quadlock and see if either headunit will powerup using the button as that should work regardless of if the CAN-bus side is working

I have now double checked all relevant fuses in engine bay fuse box, so F8 = 15a radio fuse, F12 = 5a Can databus, checked power at rear block connector as suggested and getting around 7v at both positive connections.

 

Tried both my Bolero and Stream head unit with and without the aerial connected and still no joy, it feels like it’s a simple fix but I can’t put my finger on the problem!

 

I’m thinking if the antenna base is shorted out/doesn’t work that may render the head unit to not respond, I did find when I connected the Bolero the first time it wouldn’t switch on with just the block connector connected, as soon as the antenna cable was plugged in it came to life.

 

If the Can databus is shot is it a case of find one used and plug it in or would I have to get it programmed?

 

Sorry for all the questions but it’s driving me mad!!

[langers2k]

46 minutes ago, murkey said:

checked power at rear block connector as suggested and getting around 7v at both positive connections.

 

That's too low... It should be very close to the battery voltage so above 12v.

 

 

I would check the battery voltage and check the voltage either side of fuse F8 to see if you can narrow down where the voltage drop is happening.

 

I'd also try a different ground point to make sure it's not the ground path that's causing issues.

 

[murkey]

1 hour ago, langers2k said:

 

That's too low... It should be very close to the battery voltage so above 12v.

 

 

I would check the battery voltage and check the voltage either side of fuse F8 to see if you can narrow down where the voltage drop is happening.

 

I'd also try a different ground point to make sure it's not the ground path that's causing issues.

 

 

Thanks for all your help so far..

 

Moving on, I checked Fuse F8 radio and its just over 12+V so all good, checked block connector again, 8.6V??

 

Now the ignition switch made me think again so I swapped that back to the original that was temperamental, checked the block connector again 12+V - great, plugged Bolero back in - nothing, tried Stream unit again nothing, unplugged and check block connector again back to 8.6V - what is going on!

 

As a last chance I put the new ignition switch back in but block connector read the same 8.6V.. All this from undoing the amplified antenna without unplugging it.

 

I'm at a loss now so I have put it all back together and I'll have to drive without no radio until I decide what to do next - very frustrating but thanks for your replies so far.

[langers2k]

Both should be permanent live so 12v regardless of the ignition switch.

 

At a guess, you have a damaged wire or joint and when you're moving the loom, it's making a high resistance fault.

 

I'd probably try measuring the voltage while moving the loom around next.

[murkey]

Further to my problems I have an update, this morning while giving my lad a lift to school the Bolero sparked into life!

 

Yesterday in all that heat it was so frustrating, everything I tried and had silly in between volt readings with nothing working, I felt for sometime it was to do with the CANbus, after all it does control the on/off function of head unit, maybe leaving it overnight and taking it for a drive this morning reset it?

 

Messing with the amplified aerial while connected defiantly messed it up as I watched it flicker and go blank while I was unscrewing the 22mm nut, so lesson there - make sure everything is off and unplugged before metal to metal contact!

 

Thanks Langers2k for your replies, it was much appreciated