Metra 70-8113 Harness - Grounding Noise

[pdxlc]

Just installed a Pioneer headunit into a 2000 LC (non-nav) using the Metra 70-8113 wiring harness that utilizes the stock amp and speakers.

I was aware of the possible noise that can occur when using the stock amp with an aftermarket headunit due to the isolated ground from the stock amp (Metra black/white wire).

In trying a variety of ground wiring connections, the arrangement that seemed to make the least amount of noise was tying all grounds together ( black and black/white from Metra, ground from headunit, RCA pre-amp outputs and separate ground to chassis). This reduced the speaker "hiss" considerably, but I still get a minor "pop" when powering the headunit on and off.

Assuming this is a grounding issue, has anyone been able to get rid of the pop with this configuration? I don't want to bypass the stock amp and lose the stock sub.

All feedback welcome...

 

[gregnash]

This is a known common issues with these systems and has to do with the factory amp and grounding circuit. I have it in my 98 with the Metra 70-8112.
I have scoured through all the different threads and the only way to get rid of it is to bypass the factory amp all together. I have both the hiss and pop that you speak of, for me this setup in its current state is nothing more than a temporary solution while I handle other stuff.

 

[archerwolf]

Scosche TA-03 Wiring Kit Noise Mod

Left: Original Scosche TA-03 (came w/BlueBox) Middle: Scosche TA-03HB (harness only/no BlueBox) Right: Best Kits BHA8113 identical to orig TA-03 (search eBay) Note: orig harness (left) doesn't have a shell covering the pins so it's easy to mod, newer harness (middle) has the extended shell...

www.newcelica.org

This old thread is a how-to on wiring in resistors to the Scosche harness (same as the Metra 70-8112). The resistors act like a high-pass filter, dumping all that noise into the ground. This will work to eliminate the hiss/pop if you really want to keep that stock amp/sub.

I just bypassed the stock amp and I'm pretty happy.

 

[brauski]

I just had a similar issue but with an aftermarket amp. I ended up running a wire from the headunit to the amp ground point instead of using the Metra harness for that. If you're using the stock amp you may need to splice a wire, but that concept should work. It can't loop if it's one connection.

 

[pdxlc]

I just had a similar issue but with an aftermarket amp. I ended up running a wire from the headunit to the amp ground point instead of using the Metra harness for that. If you're using the stock amp you may need to splice a wire, but that concept should work. It can't loop if it's one connection.

Interesting, so you ran a ground wire directly from the amp ground to the headunit ground?

 

[brauski]

Interesting, so you ran a ground wire directly from the amp ground to the headunit ground?

Yup. Ran it down into the center console, then out the side under the carpet under the passenger seat (was easy as I had just reinstalled the carpet after some work). I reused the stock ground location on the chassis for the aftermarket amp, the headunit, and tied the parking brake bypass in with it too. Was probably about 3-4ft of 12ga I covered with that metal braid sleeving then wrapped in fabric loom tape to keep it safe.

 

[pdxlc]

Scosche TA-03 Wiring Kit Noise Mod

Left: Original Scosche TA-03 (came w/BlueBox) Middle: Scosche TA-03HB (harness only/no BlueBox) Right: Best Kits BHA8113 identical to orig TA-03 (search eBay) Note: orig harness (left) doesn't have a shell covering the pins so it's easy to mod, newer harness (middle) has the extended shell...

www.newcelica.org

This old thread is a how-to on wiring in resistors to the Scosche harness (same as the Metra 70-8112). The resistors act like a high-pass filter, dumping all that noise into the ground. This will work to eliminate the hiss/pop if you really want to keep that stock amp/sub.

I just bypassed the stock amp and I'm pretty happy.

Thank you for this...I grounded the RCAs as shown in the schematic, but did not use resistors. Grounding the RCAs did reduce the hiss substantially, but didn't eliminate the pop when powering on/off.