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Ask Don 'Mo Lurch' Your Own Que...
Don 'Mo Lurch'
Don 'Mo Lurch', Car Electronics Technician
Category: Car Electronics
Satisfied Customers: 20893
Experience:  over 30 years, ARA, Sony, Alpine, Audiovox, Kenwood, Muntz. Sales, Repair & Installation
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It's the Mercury is it supposed to have common ground

Customer Question

It's the Mercury is it supposed to have common ground wireing ? There's a picture
Submitted: 1 year ago.
Category: Car Electronics
Expert:  ElectronicsPete replied 1 year ago.


Yes, there will be a common ground wire.

You can test for continuity to ground with an ohmmeter or continuity tester.

Customer: replied 1 year ago.
I don't have one of those.... Is there a diagram for it it's a 1990 Mercury topaz
Expert:  Don 'Mo Lurch' replied 1 year ago.

Because of the "same color" wires for Speakers, you will have to "pop" each "pair" of Speaker wires to find the correct matching pair
I use a AAA Battery
Briefly touch the wires to the Battery (+) & (-)
Example: Dark Green / Orange wire to (-)
Pink / Light Blue to (+)
The "pair" that make a scratchy or pop sound in the speaker will be the correct pair for that speaker
NOTE:.......In some Ford / Mercury vehicles they tied the Speaker Grounds together at other points
You would have to run new wires or locate a Floating Ground to Common Ground Speaker Adapter


Customer: replied 1 year ago.
Could you tell me the drivers side back speaker and the front speaker wires. I believe it's supposed to have a harness already in the car but someone cut it . (Common ground wireing?) my friend got the power and illumination working but only one speaker. It's the passenger side back speaker. The deck is pioneer deh-x6600
Customer: replied 1 year ago.
Expert:  Don 'Mo Lurch' replied 1 year ago.

did you not look at the diagram I posted?
It shows the Factory Colors

Customer: replied 1 year ago.
Sorry I just got confused because not all the colors matched the wires in my car .
Expert:  Don 'Mo Lurch' replied 1 year ago.

since we are not able to see or touch the vehicle it is always best to provide as much info as possible
Year, Make, Model, Engine, Transmission, Factory Radio Model Number or Part Number, New Radio Brand & Model Number, Wiring Adapter, experience, etc.
The difference between "Floating Ground" & Common Ground is that "Floating Ground" uses Radio Internal Electronics to provide the Ground for each Speaker & the Speaker Grounds "CANNOT" be grounded to the Vehicle or vehicle ground wires.
Common Ground provides Ground thru the Vehicle & / or Vehicle Ground wires.
Most vehicles & Radios now have "Floating Grounds"
Older Vehicles, like yours, used both & you have to know the wiring circuit to decide.
Ford was famous for splitting the Floating Grounds elsewhere in the vehicle, in which you would :
a) have to find the split & route from there
b) run your own grounds to the speakers
c) use a Floating Ground Adapter


I posted answers to your questions & you should be able to gain from that, unless you have damaged the Radio you are installing