Radio won't power up without the aerial connected

Pond

Zorg Guru (III)
British Zeds
Joined
Dec 26, 2016
Points
144
Location
Spaldingski, Lincs
Model of Z
Z3 project and E89 Z4
As per the title.......why?
I have a new stereo for the car and thought I would check it works today. The connectors are the same as the old one; previous was an Alpine aftermarket and new is a JVC, but I don't have an aerial extension connector so thought it would be OK. I couldn't get the new one to power up. So I plugged in the old Alpine and with the aerial connected it works fine but without it won't fire up either.

The weirdest thing is that with either connected and the aerial unplugged, there is a constant 'clicking' from the PCB in the nearside footwell speaker.

I can't see how the aerial has anything to do with power to the radio, as it has it's own earth.

I hate 12v DC, it doesn't make any sense to me!
 

Stevo7682

Zorg Expert (I)
Supporter
The M44 Massive
Scottish Zeds
Joined
Apr 1, 2016
Points
208
Location
Maybole , South Ayrshire
Model of Z
Z3 Individual Dakar / Orinoco Individual
Stab in the dark (as,its only thing I can think of )
Get a length of wire plug radio together without aerial (so in not working mode) then run wire from known good earth to radio external casing if works you have an earthing issue somewhere and the unit trying to ground through aerial .
Stephen
 

Pond

Zorg Guru (III)
British Zeds
Joined
Dec 26, 2016
Points
144
Location
Spaldingski, Lincs
Model of Z
Z3 project and E89 Z4
Stab in the dark (as,its only thing I can think of )
Get a length of wire plug radio together without aerial (so in not working mode) then run wire from known good earth to radio external casing if works you have an earthing issue somewhere and the unit trying to ground through aerial .
Stephen
Good idea, thanks. :thumbsup:
 

Rudyrov

Zorg Guru (I)
American Zeds
Joined
Jan 29, 2014
Points
95
Location
Phoenix, AZ
Model of Z
2.8 L Roadster
The radio is getting ground through the antenna shield wire is the most likely scenari.
It is ok and wont hurt anything, there should be a ground wire in the radio harness, perhaps it’s not connected or not used. There are a variety of reasons for this including unwanted radio noise control or ground loops.
 

Pond

Zorg Guru (III)
British Zeds
Joined
Dec 26, 2016
Points
144
Location
Spaldingski, Lincs
Model of Z
Z3 project and E89 Z4
The radio is getting ground through the antenna shield wire is the most likely scenari.
It is ok and wont hurt anything, there should be a ground wire in the radio harness, perhaps it’s not connected or not used. There are a variety of reasons for this including unwanted radio noise control or ground loops.
Looks like this was the case. I had no earth to the radio in the wiring loom from the car, although there was a wire connected (but it isn't brown!).
So I have diverted the earth from the radio connector directly to an earth post on the car. Sorted and works a treat.

Many thanks guys. :thumbsup:

I also have a blown rear speaker, so I am going to replace both rears. I just hope the dodgy radio wiring isn't the cause of the speaker blowing.
 

Duncodin

Zorg Guru (III)
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Sep 8, 2021
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139
Location
Pontrhydyrun - in Crow Valley
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M44 FrankenZed
Look at the wiring diagram. The radio earth wire goes right back to the bracket of the aeriel. If that wire isn't connected to the frame then i guess your only earth is the shielding of the ariel cable.

Some people may, over the years, have earthed their radio somewhere under the dash but from the factory it's that long brown wire going to the aeriel bracket.
 

Pond

Zorg Guru (III)
British Zeds
Joined
Dec 26, 2016
Points
144
Location
Spaldingski, Lincs
Model of Z
Z3 project and E89 Z4
Look at the wiring diagram. The radio earth wire goes right back to the bracket of the aeriel. If that wire isn't connected to the frame then i guess your only earth is the shielding of the ariel cable.

Some people may, over the years, have earthed their radio somewhere under the dash but from the factory it's that long brown wire going to the aeriel bracket.
As I said I have a wire in the loom connector where the earth should be but it isn't brown (can't remember the colour and don't really care).
It looks like the loom has been modified, presumably when the aftermarket stereo was fitted. I don't know and am not going to pull apart the loom just for the radio. A radio, for me, is just an added bonus; not critical to my build.

I now have it all working with the aid of some new rear speakers (luckily I have a Halfords 300 yards away). The radio doesn't work as I know my aerial is knackered. I may, or may not, look at that in future. I can play music through a USB stick which is enough for me.

I only tested the stereo to make sure it fits behind the new dash in the glovebox. I had to buy a 'short chassis' head unit but it was still very tight. All good, all fits and all works. Onto the next problem!
 
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