Dimmer-related noise

Pittdawg

Original poster
Member
Dec 5, 2011
538
Do you know if the dimmer switch connects to the instrument panel or otherwise is run off of one of these stepper motors? I ask because after installing my aftermarket nav/stereo, I get terrible feedback from the driver's side tweeter when the dimmer switch is turned on. I also have a faint ticking coming from behind the instrument panel and I am curious as to whether or not this is all stepper motor related.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
I gave your post a new thread to avoid hijacking.

1) Ticking can be stepper motor or HVAC actuator related. Turn off the HVAC system and see if the sound goes away.

2) The dimmer switch runs a square wave of varying duty cycle through all the lamps and LEDs in the instrument panel. Either something in your new head unit isn't properly shielded, or the tweeter is picking it up from adjacent wiring of the dimmable lamp power busses. Try removing the dimmable lamp wire from the head unit and see if the crosstalk is coming from inside the unit.
 

Pittdawg

Original poster
Member
Dec 5, 2011
538
the roadie said:
I gave your post a new thread to avoid hijacking.

1) Ticking can be stepper motor or HVAC actuator related. Turn off the HVAC system and see if the sound goes away.

2) The dimmer switch runs a square wave of varying duty cycle through all the lamps and LEDs in the instrument panel. Either something in your new head unit isn't properly shielded, or the tweeter is picking it up from adjacent wiring of the dimmable lamp power busses. Try removing the dimmable lamp wire from the head unit and see if the crosstalk is coming from inside the unit.

I was going to simply bypass the bose amp as you originally suggested, should I still try this out or do you think its not worth the try anymore?
 

Pittdawg

Original poster
Member
Dec 5, 2011
538
the roadie said:
I suggested something and you didn't try it yet? :wink:

Let's see if a true audio expert pick up on the thread.

Ha! My ported throttle body took precedence...:raspberry:
 

Dad-O-Matic

Member
Dec 5, 2011
228
Pittdawg said:
after installing my aftermarket nav/stereo, I get terrible feedback

This is related to three problems I had with my installation.

What brand of adapter did you use? I used Metra/Axxess and their instructions are lacking. One instruction said to connect two different wires to the amp turn-on signal, had to email them to find out one instruction was extraneous. Unfortunately they don't provide a wiring diagram.

I also connected the VSS signal back on itself due to unclear instructions creating feedback to my speedo causing it to jump all over the dial. Cutting the wire from the adapter fixed the problem.

I also noticed that the dimmer signal had two org/wht wires, one from the adapter harness and one from the GMOS "black box". The instructions don't say which to connect to the stereo and I didn't want another feedback scenario so I just hooked up the harness side. Doesn't work. Maybe you did as I did with the VSS and created a feedback loop on the dimmer signal. Just a thought.

the roadie said:
The dimmer switch runs a square wave of varying duty cycle through all the lamps and LEDs in the instrument panel.

That may explain why the dimmer on my stereo doesn't work. I guess the GMOS takes the square wave dimmer signal and converts it to straight DC so that the aftermarket stereo can "read" it. Sounds like I've got my dimmer is connected to the wrong org/wht wire. Luckily I foresaw such a problem and put quick connects on both wires, I just haven't had time to switch them over.
 

Pittdawg

Original poster
Member
Dec 5, 2011
538
Dad-O-Matic said:
This is related to three problems I had with my installation.

What brand of adapter did you use? I used Metra/Axxess and their instructions are lacking. One instruction said to connect two different wires to the amp turn-on signal, had to email them to find out one instruction was extraneous. Unfortunately they don't provide a wiring diagram.

I also connected the VSS signal back on itself due to unclear instructions creating feedback to my speedo causing it to jump all over the dial. Cutting the wire from the adapter fixed the problem.

I also noticed that the dimmer signal had two org/wht wires, one from the adapter harness and one from the GMOS "black box". The instructions don't say which to connect to the stereo and I didn't want another feedback scenario so I just hooked up the harness side. Doesn't work. Maybe you did as I did with the VSS and created a feedback loop on the dimmer signal. Just a thought.



That may explain why the dimmer on my stereo doesn't work. I guess the GMOS takes the square wave dimmer signal and converts it to straight DC so that the aftermarket stereo can "read" it. Sounds like I've got my dimmer is connected to the wrong org/wht wire. Luckily I foresaw such a problem and put quick connects on both wires, I just haven't had time to switch them over.

I am using the metra/axxess module as well. I'm actually taking it into a stereo shop for them to re-wire. What exactly should I tell them to fix the feedback issue?
 

Dad-O-Matic

Member
Dec 5, 2011
228
Pittdawg said:
I am using the metra/axxess module as well. I'm actually taking it into a stereo shop for them to re-wire. What exactly should I tell them to fix the feedback issue?

Can't say for sure, but if the dimmer signal from the harness (truck side) is connected to the dimmer signal from the GMOS side, I'd think that would create some feedback.

In my scenario I've got 3 orange/white dimmer wires: 1 from the truck harness, 1 from the GMOS adapter and one from the stereo.

If I'm right the GMOS wire should go to the stereo and the truck harness wire should be left disconnected and taped up. Doesn't make sense that the aftermarket head unit would use a PWM signal, probably just straight DC. I'll know for sure when I can get out there to swap the wires.
 

Pittdawg

Original poster
Member
Dec 5, 2011
538
Dad-O-Matic said:
Can't say for sure, but if the dimmer signal from the harness (truck side) is connected to the dimmer signal from the GMOS side, I'd think that would create some feedback.

In my scenario I've got 3 orange/white dimmer wires: 1 from the truck harness, 1 from the GMOS adapter and one from the stereo.

If I'm right the GMOS wire should go to the stereo and the truck harness wire should be left disconnected and taped up. Doesn't make sense that the aftermarket head unit would use a PWM signal, probably just straight DC. I'll know for sure when I can get out there to swap the wires.

If you get to it before this Thursday, let me know. Thanks.:thumbsup:
 

Dad-O-Matic

Member
Dec 5, 2011
228
Pittdawg said:
If you get to it before this Thursday, let me know. Thanks.:thumbsup:

Sorry couldn't get to it before Thursday, but my theory was correct, I switched the wires and my dimmer works as it supposed to.

Edit: No noise from the dimmer on my setup. Perhaps the GMOS is the problem?
 

Pittdawg

Original poster
Member
Dec 5, 2011
538
Dad-O-Matic said:
Sorry couldn't get to it before Thursday, but my theory was correct, I switched the wires and my dimmer works as it supposed to.

Edit: No noise from the dimmer on my setup. Perhaps the GMOS is the problem?

It was the gmos. I had to buy and expensive PAC model.
 

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