Today I wanted to troubleshoot the power antenna in my '77 240D. It is an Hirschmann Auta 6000U typ 485.
My car has an aftermarket Pioneer radio, so I know that the trigger wire was disconnected.

I tried to bypass that by jumping between +12V and pin number 2 on the connector harness.

Unfortunately that did not work, so I removed the jumper wire and put it back together.

Now with the Hirschmann antenna in its original configuration (no jumper wire) I hear the solenoid clicking on and off every couple of seconds, even with the key and car off. The assembly also got somewhat warm and the interior dome lights were flickering.

I think I must have fried the board somewhere. I see there are 3 capacitors, 1 inductor and the solenoid on the circuit board.

Is there any way to troubleshoot these components to see which one I need to replace? I have a DMM and measured 1uF, 1uF and 4.7nF. I think the capacitors are good.
So what could be causing the DC motor to heat up? This was not happening before I tried to bypass the radio trigger wire.

The circuit boards part number is 720 393.

Thanks!