Loud thimb from factory sub after head unit install

[Derrick Townsend]

Hey guys i just installed my new in dash tv in my 07 but know my sub is making a loud thump everytime i turn the car on. Is this a ground problem? Im using the crutchfield harness. I also used the harness ground to ground the e-brake cable. Could that be the problem?

 

[A1cntrler]

The problem is that your factory amplifier uses 5v for the remote, and your new HU is putting out 12v. You need some sort of relay to drop the voltage on the remote wire from 12v to 5v. I think that will solve the problem, but let's see what some others recommend...

 

[Derrick Townsend]

ttt. thanks

 

[Pat Freeman]

My installer put some resistors (75k ohms?) on a wire to bring the voltage down, but can't remember which one. I think he said the signal wires leaving the unit (sub out) as these were supplying immediate signal to the sub during AVIC power up. My AVIC-Z1 still thumps the sub when the AVIC powers up but not all the time and not always very loud. He said he could make the noise much less with more resistors but it wouldn't power the sub.



I'm not sure switching to 5V would fix this. You could always go with a model 7805, 5V regulator, if you wanted to and see if that works. This regulator would put out some heat, tho.

 

[Frank Marano]

any remote lead from a headunit should already be 5v........:blink:

 

[Tony Tassillo]

actually the headunit puts out a 12v lead .5amp what you will need to do is to put a 1k ohm resistor inline on the remote feed to bring the voltage down to 5v to eliminate the turn on thump.