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10/26/13 3:52pm - Original Message: 'Constant 12 volts for new radio'
dapperdan
Former Member
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COLUMBUS, NC - USA

Vette(s):
2011 Grand Sport Coupe, 6-speed 1977 Coupe L82, 4-speed

Joined: 8/19/2012
Posts: 42
I'm putting a new radio in my '77.  It requires 2 sources of power, one constant 12 volts for the clock and one "accessories" which is on when the ignition in on.  The three-wire plug into the original radio has a black (ground), yellow (accessories), and a gray, which is not indicating any voltage.  Should that be the constant 12 volts?  If so, any help on why it is not hot.  If I have to get constant 12 volts from some other splice, please guide me to the proper wire (color) and where it is located.  Thanks!



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10/26/13 6:10pm - Reply: 'Re: Constant 12 volts for new radio'
Case75
Former Member
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, - Canada

Vette(s):
1975 Corvette 383 stroker w/Patriot 190 heads, Eagle stroker kit, Comp 279TH7 cam, DUI distributor, Edelbrock 7116 intake, Edelbrock 1806 carb, Hedman Hedders, TH400 w/TCI Breakaway 2400 stall, Transgo 1-2 shift kit.

Joined: 6/19/2012
Posts: 230
The gray wire is for the light inside the radio at night. Turn on your lights and check the wire for voltage after that. The cigar lighter/clock would have a constant 12 volts.

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Build Date: May 7, 1975. 383 w/267 RWHP/310 RWTQ
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10/26/13 7:22pm - Reply: 'Re: Constant 12 volts for new radio'
rraider1
Former Member
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Woodland, WA - USA

Vette(s):
1977 T-Top,350,Auto Black Ruby Pearl,Steeroids R&P conversion

Joined: 10/14/2003
Posts: 1152
The Gray should be for lights for the old radio. turn your headlight sw on and you should see 12 v then.
 
You will have run a new wire either from the battery direct through the center console or off the fuse box. with your meter or a test light you can find the ones that are hot all the time.
 
 


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Bob R
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10/28/13 9:19pm - Reply: 'Re: Constant 12 volts for new radio'
JoeTrecca
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Charlottesville, VA - USA

Vette(s):
1978 Silver Anniversary L82 Previously: 1965 300hp Coupe in 1967. 1967 435hp Coupe in 1968-70. 1969 350hp T-top w/ac and all power options.

Joined: 9/3/2010
Posts: 103
Hi Dan,  The color of the constant 12v wire to the cig lighter is Orange. If you choose to run a new wire from the battery positive terminal, I suggest that you use an inline fuse (10 amp)close to the battery connection. This fuse will protect the wire from meltdown should it short to ground.

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Joe T
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10/28/13 10:58pm - Reply: 'Re: Constant 12 volts for new radio'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 830
I'll second Joe's comment - inline fuse close to battery is definitely a good thing.  A 12 ga wire directly connected between an almost infinite current source (e.g. a car battery) and ground will get very hot very quickly.  I have some small jumper wires for electronics (used them to bench test my clock) that have the insulation burned off and they were only inadvertently connected for a second or less!  

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1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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10/29/13 11:56am - Reply: 'Re: Constant 12 volts for new radio'
74-454 Lifetime Member
Lifetime Member
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, - Canada

Vette(s):
Coupe 74 - 454 Drive it like you stole it!

Joined: 8/6/2004
Posts: 533
I simply tapped into the cig/lighter (orange) wire.  This way, no need to run a wire under the carpet and no need for in-line fuse.

I also have a cut-off switch at the battery terminal since the clock (and possibly the radio clock as well) drains the battery in a few days.  The downside of using the cut-off switch is that my radio settings are not retained.


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10/29/13 3:59pm - Reply: 'Re: Constant 12 volts for new radio'
dapperdan
Former Member
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COLUMBUS, NC - USA

Vette(s):
2011 Grand Sport Coupe, 6-speed 1977 Coupe L82, 4-speed

Joined: 8/19/2012
Posts: 42
I found that the positive post on the clock is right there on the back of the instrument cluster.  I merely tapped into the 12v supply with a round connector and about 12 inches of wire with a lag connector to the wiring harness for the new radio.

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