Stock amp important for radio reception?

[John 535is (Sydney)]

there is a thin white wire that comes off the car harness (switching via the radio volume on/off) that powers both the amp and power antenna which is integral to the rear defogger. If you disonnect your amp be sure to keep switching power to your powered antenna in the rear glass.
HTH,
George

My head unit was changed by the previous owner, reception on the radio is poor, and the defogger does not work. Could all this be related to the same problem, and what should I do

John 535is 1989 (Sydney)

[George M]

don't know if there is linkage between your defogger not working and poor reception...but possible...would have to check respective wiring diagrams in the back of Bentley. No mystery about the thin white wire that is part of the car's harness...simply a switching +12V hot that works off the radio volume on/off knob.
Turn the radio on and the thin white wire becomes hot and powers both the amp in the trunk and the power antenna that is integrated into the defogger. You may want to pull your radio and see if this connection were made properly. Quite common for an aftermarket radio be installed and miss this step. Bentley should show the white wire that connects to both remote amp and antenna.
HTH,
George

[MikeV]

The PO had a dog (you should have seen the sorry state of the leather!), who apparently scratched most of the defogger traces....
I made the mistake of trying to repair the scratches with a copper/silver-epoxy kit.... unfortunately this introduces a great amount of noise in the radio reception when the defogger is on....

[Kennan]

No mystery about the thin white wire that is part of the car's harness...simply a switching +12V hot that works off the radio volume on/off knob. Turn the radio on and the thin white wire becomes hot and powers both the amp in the trunk and the power antenna that is integrated into the defogger.
HTH,
George

From the beginning, I was planning to use the white wire as the remote turn on. From your previous post, you make it seem that power needed to be supplied to the white wire itself so I was a bit confused.

Sorry for all the questions, but do I use the white wire as the remote turn on or do I need to supply 12v to this white wire?

[RobPatt]

new head unit probably has a blue wire which is not connected, typically used for remote turn on of an external amp.... take this blue wire....
... find the white wire in your factory radio harness.... connect the blue wire to it..... that will give your antenna amp power and greatly increase radio reception.... I'm using that white wire for the antenna amp (as should be) and will use to remote turn on a powered sub (infinity basslink)... my stock amp is GONE, I've got new head unit, and infinity kappa components in front... rear infinity basslink soon to come.

hope this helps.