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Username Post: Three-wire vs Four-wire Tail Light Systems        (Topic#342308)
GreatNorthWoods 
"4th Year" Silver Supporting Member
Posts: 755
GreatNorthWoods
Age: 75
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
01-30-17 07:00 AM - Post#2674294    

My 53 Chevy has an EZ Wire Wiring Harness. The tail lights are a 3-wire system. That is, the turn signals and brake lights are combined. I installed a third brake light on my car but it doesn't operate the way I want it to. Since the brake and turn signal wires are one and the same, the third brake light blinks when I make a left turn instead of remaining steady. A 4-wire system has separate brake and tail light wires. Most vehicles with amber turn signals have a 4-wire system. As such the amber lights do not come on when the brakes are applied. My thought is that I might be able to convert my system to a 4-wire by simply cutting the power from the brake light switch going to the tail lights and running a separate wire directly from the brake light switch to the brake filament of the tail lights and to the third brake light. This would also allow me to run separate amber directional signals if I chose to. What say all you electrical experts? Will this work? I do not want to get too deep into the wiring harness or replace it but if I can accomplish this by running a single wire to the rear for brake lights I would like to do that. I am fairly competent with automotive wiring but this is a situation I have not encountered previously.

Vern

1953 Chevy Belair Sport Coupe - 350 Crate Engine,700-R4, Vintage Air, EZ Wire, Ididit column, Cruise/Tilt, 4-Wheel Disc Brakes, Nova 10-bolt, Chassis engineering front suspension.


 




monty56 
"14th Year" Gold Supporting Member
Posts: 1380
monty56
Loc: Chandler(it's a dry heat)...
Reg: 04-26-04
01-30-17 09:26 AM - Post#2674326    
    In response to GreatNorthWoods

My EZ-wire harness came w/ a third brake light wire, but since they don't supply a wiring diagram with the kit I couldn't tell you where it is fed from.

Monty
'56 3100 Short Stepside Someday
2001 Chevy Suburban 2500
2009 Saturn Vue w/20's

Member: Desert Classic Chevy's Inc.
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Avatar is my Truck


 
65_Impala 
Very Senior Member
Posts: 3928

Reg: 12-29-02
01-30-17 09:44 AM - Post#2674332    
    In response to GreatNorthWoods

The signal switch does the magic of creating the combined brake/signal wires.

Take the brake switch input away from the signal switch and the signal switch will only make the connected light bulbs flash.

Run the brake switch directly to a brake light and it will only light when the brake pedal is pushed.



 
GreatNorthWoods 
"4th Year" Silver Supporting Member
Posts: 755
GreatNorthWoods
Age: 75
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
01-30-17 10:16 AM - Post#2674338    
    In response to 65_Impala

That's what I was thinking. Just wanted someone to corroborate...

Vern

1953 Chevy Belair Sport Coupe - 350 Crate Engine,700-R4, Vintage Air, EZ Wire, Ididit column, Cruise/Tilt, 4-Wheel Disc Brakes, Nova 10-bolt, Chassis engineering front suspension.


 
GreatNorthWoods 
"4th Year" Silver Supporting Member
Posts: 755
GreatNorthWoods
Age: 75
Loc: Littleton, New Hampshire,...
Reg: 03-31-02
01-30-17 10:19 AM - Post#2674339    
    In response to monty56

It would have to be fed from the brake light switch but I think a PO might have either removed the third brake light wire from the harness or it's buried somewhere in the harness never to be found. I didn't wire the car. It came to me this way...

Vern

1953 Chevy Belair Sport Coupe - 350 Crate Engine,700-R4, Vintage Air, EZ Wire, Ididit column, Cruise/Tilt, 4-Wheel Disc Brakes, Nova 10-bolt, Chassis engineering front suspension.


 
CowboyTrukr 
"6th Year" Silver Supporting Member
Posts: 3822
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
01-30-17 12:07 PM - Post#2674361    
    In response to GreatNorthWoods

You can do this. Take a fused tap (hot always) and feed it to the brake switch. From the switch take the new supply back to the tail lamps. The other side of the lamps should already be grounded.

You could unburden the brake switch and add a 30A relay to the mix.

Greg

'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500
'00 Explorer XLT 4.0 V6 Auto
'94 K2500 5.7 NV4500 ECLB - SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 




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