Becker Mexico Electronic 784 & power antenna - 1978 SL

[IdlePhaedrus]

Hi All,

Newbie here looking for some help.

I have a 1978 450SL built in South Africa. It has a Becker Electronic Mexico model number 784. I cannot find any information on this particular unit on the Interwebz, but almost identical to these. (can post images if necessary)

The car has been standing for a couple of years because it needed new exhaust manifold gaskets, which are now done.

The problem I have is that the power antenna drops when the radio is turned off, and then at some random time later it will go up again. It didn't do this before.

Random time can be less than a second after the antenna starts dropping or a few hours after it has completely dropped.

I replaced the antenna, and the new one does the same. I have also replaced the battery as it was old but the problem persists. Since I replaced the battery the time between the drop and the rise has decreased.

There is an audible click from the Becker unit when the antenna rises again.

Pulled the Becker unit today, and the wiring behind the dash is a dogs breakfast, so will start tidying that up tomorrow.

Does anyone have an idea what might be causing the unit to cause the power antenna to rise again after the radio is turned off?

Any help appreciated.
Phaedrus