No Radio = No Turn Signals!

[Bruzilla]

I learned something new today. I thought the dumbest thing Chrysler engineers ever did was make a radio with both knobs on the left, but they topped even that! I found out today that the power for the turn signals is routed through the radio!!! Why they did this, I have no idea.

I've only had one 73/74 Roadrunner that had the original radio still in it before this latest one, and it still had the radio when I sold it. Last weekend I swapped the Rallye dash and took out the AM radio of my 74 Roadrunner, and lost my turn signals. I thought it was an issue with the dash, or turn signal switch, but it wasn't.

The radio plug has four wires going to it. Orange is a +12VDC that supplies power to illuminate the radio when the parking/head lights are on; red is a +12VDC switched power for the radio. The last two, black and red with a white stripe, is the +12VDC for the turn signals. If you take the radio out, you have to splice the black and red/white wires together to get your turn signals to work again.

 

[Ron 73]

That is strange and confusing, I didn't have a radio in my car until now as far as stock.. And it all worked, someone before i got the car must have by passed this, i just got a stock radio and put it in but just for looks.. I did hook the orange wire up which must be the power because the light comes on in the radio, in case i would want to hook it up someday. Never heard of this one but ive seen strange things with wiring stuff and Mopar, as i said happened to me a couple days ago in your other thread.

 

[moparmarks]

Ya something is not right with that. T/S are part of the brake light circuit. Radio does share a circuit with the B/U lights. I've had alot of 71-4 dashes and wiring apart and never seen any connection between the T/sig and the radio.

 

[Bruzilla]

That's what's so crazy about the design. The turn signals get their power through a totally different curcuit than the radio, but the power is routed through the radio. The radio has it's own power input, as does the turn signals, so the only reason I can see why Chrysler did this was to make it harder for people to use non-Chrysler radios in the cars, which was the reason for the double-left knobs.

 

[moparmarks]

Dude what I'm saying that is NOT part of the design. Have a stack of radios dashes harnesses clusters ect. 71/4B radios have the red switched power, orange dash lights and the green and black speaker wires. 72/4 AM/FM has a 3rd purple speaker wire. Some have a multi-pin connetor for the tape deck option. Then the antanna. No other wires go to or through the radio. Also have factory wiring diagrams. This red and white wire you speak of are not factory. Can you get a pic?

 

[Bruzilla]

Dude... I never said there are wires running through the radio. What I said was the power for the signals runs through the radio. My radio has the same red/yellow wires you mention, but check the plug. There's four wires that run into the radio plug: red, orange, black, and red/white.

I've already cut my wires, but I see if I can get a pic of the plug.

 

[moparmarks]

Heres a pic of another dash that I built. One of many. Sorry don't see this red/white wire on the radio.

 

[moparmarks]

If you can get a pic that would help. Sorry misunderstanding on the "through" thing.

 

[72RoadrunnerGTX]

The power for the turn signals was not routed through the radio. Disconnecting the radio at the intact factory connector will not disable the turn signals. If the radio power connector is cut off the dash harness it will be necessary to restore the original series connection between the Red/trace and black wires for the turn signals to function. These types of series connections are very common in the automotive wiring of all types.
As for the layout of radio controls on these cars, back then, all manufactures had unique radio designs based more on unique styling, long before any kind of DIN standards were adopted by US car manufactures.
There just wasn’t much in the way of aftermarket in-dash radio options back then.

 

[Bruzilla]

That's the plug right there, but I hate to tell you but my turn signals quit working once I unplugged the radio from that plug. Nothing was cut, maimed, disconnected, or had anything else done to it.

 

[moparmarks]

That is a weird one. I had several without a radio or aftermarket with no problems. The flasher is mounted right up in that area. Maybe you knocked it loose or something.

 

[72RoadrunnerGTX]

That's the plug right there, but I hate to tell you but my turn signals quit working once I unplugged the radio from that plug. Nothing was cut, maimed, disconnected, or had anything else done to it.

Fact of the matter is, with dash harness in its original state, the radio has no relation to the turn signal circuit other than the power lead (black wire)to the turn signal flasher(mounted on the passenger side of the ashtray) is crimped together with the red/traced wire at the female spade connector in the dash harness radio plug. The Red/traced wire comes directly from the fuse box, fuse labeled “RADIO, B/UP ”. All else being intact, whether or not something is plugged into the radio power connector will not interfere with turn signal function. Get out your voltmeter and trace it out, you have got something else going-on.
Your OP suggests you had to “splice“ these two wires together to restore turn signal function, fact is they were connected together at radio power spade connector originally and you may have had a problem with that crimp.

 

[68 HEMI GTS]

you can even make the radio play without the key. think you gotta turn the left turn signal on, step on the brake and maybe have the parking lights on. i can't remember without going out to the garage and trying it. my dad showed me that when i was a kid.

 

[63 Savoy]

radio

68 Hemi is right--I had a 69 cuda new and if you had the four ways on and hit the brakes the radio would play---we tried that with lots of mopars and it worked on them all---mopar has lots of backfeeds--cheaper harness--Mike

 

[72RoadrunnerGTX]

68 Hemi is right--I had a 69 cuda new and if you had the four ways on and hit the brakes the radio would play---we tried that with lots of mopars and it worked on them all---mopar has lots of backfeeds--cheaper harness--Mike

The OP’s question is not about “back-feeds” in older Mopars, big differences electrically between the older models mentioned and the 73-74' B-body in question, wiring diagram provided above. The redesign of the hazard light circuits around the 1970 model year, incorporating the hazard light switch into the turn signal switch, that when activated physically isolates the hazards light’s “un-switched” power source to prevent such “back feeding” to anything. On this car, as originally designed, the radio power source connector is wired in series with the turn signal flasher and shares the same “ACC” fuse with the back-up lights, simple as that. Unplugging the radio from its connector will not, by design, open up this circuit to the turn signal flasher, preventing turn signal function as stated in the OP.

 

[Bruzilla]

That is a weird one. I had several without a radio or aftermarket with no problems. The flasher is mounted right up in that area. Maybe you knocked it loose or something.

I would guess you're like me, where the cars you've had lost the original radio years, or decades, ago and someone fixed the problem back then. The flasher was the first thing I checked, and it was fine.

 

[Bruzilla]

The OP’s question is not about “back-feeds” in older Mopars, big differences electrically between the older models mentioned and the 73-7’4 B-body in question, wiring diagram provided above. The redesign of the hazard light circuits around the 1970 model year, incorporating the hazard light switch into the turn signal switch, that when activated physically isolates the hazards light’s “un-switched” power source to prevent such “back feeding” to anything. On this car, as originally designed, the radio power source connector is wired in series with the turn signal flasher and shares the same “ACC” fuse with the back-up lights, simple as that. Unplugging the radio from its connector will not, by design, open up this circuit to the turn signal flasher, preventing turn signal function as stated in the OP.

All of that is great in theory, but the facts are:

1. The turn signals worked fine before the radio was removed.
2. The turn signals didn't work after the radio was removed.
3. The turn signals worked again once the two wires from the radio plug were spliced together.

I would say this was an odd ball problem with my car, but the only reason I was able to fix it was I read a post over on Mopar Forums from a guy who had the exact same turn signal failure I had. The same fix that worked for his car worked for mine.

 

[72RoadrunnerGTX]

Facts are these;
1. I don’t waste my time posting theories here.
2. Those two wires were “spiced” together originally, as designed, at the single female spade connector in the dash harness radio plug.
3. If you found it necessary to restore the connection between these two wires(red/white&black) to regain turn signal function, then this crimp was bad or the connector had been damaged or cut off.
4. As originally designed, simply unplugging the radio from the dash harness at the connector in question will NOT disable the turn signals as stated in the OP.

 

[Bruzilla]

Facts are these;
1. I don’t waste my time posting theories here.
2. Those two wires were “spiced” together originally, as designed, at the single female spade connector in the dash harness radio plug.
3. If you found it necessary to restore the connection between these two wires(red/white&black) to regain turn signal function, then this crimp was bad or the connector had damaged or cut off.
4. As originally designed, simply unplugging the radio from the dash harness at the connector in question will NOT disable the turn signals as stated in the OP.

I don't like wasting anyone's time, especially my own. Your statements may well be true, but they conflict with the facts on the ground. All I can tell you is that the turn signals quit working when the radio was pulled, and started working when the wires were spliced, and this was not a problem unique to my car.

You go ahead and believe whatever you like, and any time you waste responding to this is all on you.

 

[71ChallengerSE]

If anyone knows anything about mopar wiring its 72RoadrunnerGTX