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OEM Radio Install Issue

Sat Sep 24, 2016 2:25 am

When i bought my LSC it came with an aftermarket pioneer head unit matched to the oem premium sound. The previous owner had mentioned that the original hu quit working. Wanting to revert back to oem, I recently picked an 89' grand marquis am/fm/cassette with the toggle volume E8LF i believe is the serial, the non CD changer compatible.

I installed the Merc unit using the mark oem connector and 6 pin to amp. The HU powered on but the volume output was very low, no mid or bass. Everything seems to be hooked up fine, so I'm wondering if the amp isn't functioning properly (maybe the reason for previous owner to think the oem HU was the issue?). The pioneer deck has a harness that connects its speaker outputs to the 6 pin oem amp wire and sound works fine. Im wondering if there could be an amp bypass in the trunk that was installed, and maybe just the pioneer internal amp is running the speakers now. Im just not sure how the bypass works or what to look for if there is one.

Other thing...Along with the mark oem connector there is a thicker red wire on its own that was connected to the aftermarket harness as a ground. Now that I've taken out the harness I'm not sure where is red ground normally connects. When testing the merc HU i just had the red wire touching a metal bracket inside the dash.

much appreciated!

Re: OEM Radio Install Issue

Mon Oct 10, 2016 3:44 pm

It is possible that the installer of the pioneer unit also bypassed the amp in the trunk using a bypass connector. This allowed the Pioneer HU to power the speakers without the use of the JBL amp. Common practice if the HU had a high power amp built in. The radio you got needs the amp and will not power the speakers itself. Check in the trunk to see if indeed the amp is connected and not bypassed 8-) ......

Re: OEM Radio Install Issue

Sun Jan 22, 2017 2:51 pm

Hey Connor,

You have PM.

OEM Radio Install Issue

Sat Sep 23, 2017 4:51 pm

Does anybody know the factory radio diagram or where i could find one for FREE on the internet? please help
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