Bench testing a radio, need to identify which wires are pos/beg.

[72 Challenger]

Hi folks,

Looking to verify if a radio I have on hand is in working order or just a good looking dud.

Am only Motorola unit 2884759. My tag on it says it came from a 74 cuda, it's going into a 72 chally.

From the picture below which wires are pos/neg. both for the larger connector that goes to the radio and the smaller connector and loose wire that goes to the speaker.

I assume for speaker wires Black is negative?

Looking to bench test it with a car battery.

[Chryco Psycho]

Red is 12v +
Orange is dash lighting
Green is speaker +
Black is speaker neg
ground is through chassis

[750-h2]

To test with a battery would you place the negative battery wire on the radios metal casing or is there designated location to ground it?   Thanks!

[Chryco Psycho]

The steel body of the radio is ground so you could set the radio on the negative post or use a jumper to the steel case of the radio to the battery negative post .

[fc7cuda]

The steel body of the radio is ground so you could set the radio on the negative post or use a jumper to the steel case of the radio to the battery negative post .

I usually run a jumper wire from the neg. battery over to the rear mount stud.

Good luck and hope the radio works. 

[72 Challenger]

Someone else asked my follow up question!

Will I hurt it if I run battery power to test if the light works?

Thanks guys!

[Chryco Psycho]

No , it is a 12v light

[72 Challenger]

Thanks for the help guys, she works! Both light and radio. Just need to hook the antenna up.

[Chryco Psycho]

Great , now if only there was something decent to listen to on AM

[72 Challenger]

My guess is that it will remain off the majority of the time.

I rather listen to my engine than the knuckleheads on news/sports talk radio.