Aftermarket subwoofer problems

[Toddi]

The Bose sub in my 2004 CS had had its amp blown from water getting into the bottom of the trunk when I got the car so I decided to install a better sub. I'm not using the spare tire so I plan to use all the space underneath the luggage compartment for a subwoofer. I figured out the wiring for the subwoofer, but am having troubles with the power sense output that should turn the subwoofer amp off when the car is off.

When measured it gives a signal, but in the range of 10v when the car is switched on, 0v when switched off.

However when connected to the aftermarket amplifier it shows only a few volts, in the range of 2-3v and the amp does not turn on. So I decided that the amp sense input was pulling the output down from the stereo by drawing too much current.

Thus I installed a relay and the same thing happens! The relay only draws a few hundred milliamperes at most so, it shouldn't be a problem.

I think that when the original Bose amp blew it messed something up on the head unit - or whatever is sending the power sense signal.

Can anyone shed a light on where this signal is coming from and where I would go to find what to fix?

Thanks,

Thor