'77 Vandura radio not working

heartbraker666 said:

Another pic

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AuroraGirl said:

so wired directly to the battery sounds like they werent using the Radio tap on the fuse panel. @Turbo4whl were you an expert on the fuse panels? Someone here is very knowledgeable. Im thinking the switched ignition is the tap, and the fuse itself is the constant.

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Turbo4whl said:

Taylor, since you asked, the old GM fuse panel had some hidden features. You can easily see in @heartbraker666 picture the 3 vertical fuses at the bottom are key on switched. Hidden feature #1: The radio will not work if the backup lights have a short and burn the fuse. This is a safety feature to let you know you have no backup lights.

Moving to the headlight switch, it has several power feeds, all are hot all the time. Easy to see in the fuse panel the taillight and parking light fuse. The brake light fuse also feeds the headlight switch for the dash lights. Current through the panel resister, back to the fuse panel at the 3 amp fuse, then to the gauge cluster light and radio light. (factory radio) This is hidden feature #2: Panel lights out, maybe no brake lights. The next power feed to the headlight switch for the headlights, no fuse. The headlights have a circuit breaker. Where is this... in the headlight switch! This feature #3, allows the headlights to re-light if the short is intermittent.

Don't want to forget the last headlight switch power feed. It is from the dome lights, hot all the time, so the switch completes the ground. Yeah, headlight switch has a ground wire, or the mounting bracket will ground it.

For Allie back to the radio. Factory radio has a 6 or 8 connection gang plug. Some people don't use it for a aftermarket radio. Some others will cut it off and butt connect wires. You can, or could use a jumper plug that matches the GM plug too.

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AuroraGirl said:

Also, what are those ugly colors on the fuses for?

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heartbraker666 said:

Wow thanx. Great info.
After investigating, I found that it has been butt connected and it must have a bad ground somewhere. I reconnected the wiring , the radio worked great.. drive a couple miles then it cut out again.

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Grit dog said:

Great explanation by @Turbo4whl ! Feel like I need to save that info somewhere. Thank you!
@heartbraker666 just gonna need to straighten out the wiring. And decide if you want to restore OE wiring locations or not.
I would not, but may use oe switched wires to drive a relay to good power, since 70s wiring and fuses etc weren’t likely sized for a radio like that that probably pulls more juice because it has a bigger amp.
On another note, that is about the cleanest original everything especially under the dash I’ve seen. Looks like you got a time capsule that never even got dusty inside!

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Turbo4whl said:

Like the mini spade lug fuses used now, the color bands on those old glass fuses indicates the amperage. Some fuse manufactures had them. No standardization.



So a guess about your older aftermarket radio. It could have a failing solder connection inside. The electronics inside heat up in use. Heat expands things and the connection opens up, the radio quits. Probably not what you want to hear. It also could be fixed, cost as much or more than a brand new replacement radio.

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heartbraker666 said:

Aw if that’s the case I’d be so bummed. I love the stereo system and would hate to change it!

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heartbraker666 said:

Aw if that’s the case I’d be so bummed. I love the stereo system and would hate to change it!

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Catbox said:

The radio should have 3 wires it needs to operate.
-Black for ground.
-Red for 12v constant power. This will be fed from the battery all the time.
-Yellow for 12v switched power. This will be switched from the key.

Then you will have the speaker wires.

This is how most work, but I have not played with a deck as vintage as yours in quite some time.
I just rewired the entire stereo in my daughters Camaro.

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Chris64 said:

This sounds backwards to me. Yellow to the battery and red to the key (accessory).

Old Pioneers had weird colors IIRC there was an orange (which is normally used for illumination) that was the constant.

But you don't have to guess, they almost always have a wiring diagram printed on top of the stereo.

If you run anything directly to the battery, be sure that line has a fuse right at the battery. If that wire gets pinched or grounded without a fuse it will be devastating.

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