Radio goes out when lights turned on

[jdavidsmi]

Good morning all, I have run into a interesting problem. Since I have owned Jolene I may have driven her at night 3 or 4 times, and I very seldom turn on the radio. But with my son here and driving her he does. Earlier this week he ran down to get some carry out. When he turned on the lights the radio went out, turn the light off the radio came back on.

This radio was in the truck when I got it and I have never done anything with it. The way I understand the wiring diagram is with the key on power is supplied to fuse #11 Circuit 137 on a Y/BK H to the radio. I should have 12v +/- where it connects to the radio. Also there is circuit 19 from the instrument cluster lighting on a LB/R with the power at the radio is variable up to battery voltage.

Voltmeter reads 13v +/- on circuit 137 and 8 to 13v +/- on circuit 19.

I know the original radio only used the two circuits.  This radio also has two power inputs (I don’t have a diagram) printed on the board one one says batt, the other says acc. And of course the ground. After tracing the wires circuit 137 goes to the battery unput, and circuit 19 goes to acc input. And ground goes to ground.

I been thinking about this for a couple of days, and I wonder if the battery input should be hot all the time and acc input goes through the key.

Any thoughts or ideas would be welcome.

[FuzzFace2]

What radio do you have installed, one of them fancy LED display types?

I have not looked or traced out the factory wiring but the way I can see a modern radio hooked up is like this.
Power all the time - fused either to the fuse box or battery  to keep stations in memory and time.

Acc and Run - this turns on the main power to the radio or powers it up. You can have it wired to have power in run and not when in ACC but if you want to listen to the radio and motor off the ICM has power going to it when not running and this is not good.

Wire from dash lights - think this is the blue/red wire. This will control the dimming of the display.

Ground - as it says goes to ground.

The factory radio I cant see needing power all the time as it does not keep stations in memory or time.

You sure you are not looking at the clock wires that is above the radio?
IIRC this will have power to it all the time, power when running / ACC, and dash light dimming.
Dave ----

[FuzzFace2]

Here is a picture of the wiring for my factory radio

This is the back of the clock but the wire colors do not match my 81 trucks wires as that clock is for a later year truck

Clock truck wires for 81 is
LG / Y = hot all the time
LB / R = dash lights
W / P = ACC / Hot in run
BK = ground

The clock has a BR (brown) that gets hooked to running lights and think I hooked it to the dash lights?
Dave ----

[BeagleRock]

 Do you mean the radio lights go off or the entire radio goes off?

[jdavidsmi]

The radio is some off brand from China I’m sure, it was in the truck when I got it. I sure the PO just found the cheapest one he could find.

The clock is plugged in and working as it should.

headlights switch is pulled out, radio goes off.

I have a hot all the time available and think of tapping into it, switching a couple of wires, and see if it fixes it.

[ArdWrknTrk]

Perhaps they tied the radio ground to brown thinking it was 'earth'?

If so, as soon as the marker lights see power there will be no potential for the radio to operate.

Take the radio ground, add an eye and screw it down to the *G701* dashboard ground to the right of the radio.

[Gary Lewis]

Yes, I think you should have hot all the time to Batt and switched power to Acc.  But I can't explain the symptom you are seeing.

[Gary Lewis]

ArdWrknTrk wrote

Perhaps they tied the radio ground to brown thinking it was 'earth'?

If so, as soon as the marker lights see power there will be no potential for the radio to operate.

Take the radio ground, add an eye and screw it down to the dashboard ground to the right of the radio.

That would explain the symptoms.

[ArdWrknTrk]

He said "ground goes to ground" but I don't know what that means...

[Gary Lewis]

I "assumed" it meant the ground wire went to the frame of the dash, which we've established recently is supposed to be ground.  But that arrangement doesn't fit with the symptoms.  Yours does.

I'm anxious to see what he finds.

[jdavidsmi]

The idea about the ground made me look further as to where the “ground” really went. The wire went into a bundle of wires behind the a/c controls. No idea where it went to after that without taking the dash apart, was not going to get into that today so I cut it, added a loop connector and the connector to a known good ground. And that fixed the problem. I really don’t know why I did not look at that before, I have had other issues that ended up being the ground.

Thanks for the help

The next project is to replace the spindle bearings on the right side and repacked the hub bearings both sides.

[ArdWrknTrk]

I'm really glad it was such an easy fix!  

It was the only thing that made sense to me.

Now you (and your son) can enjoy the radio day and night.

[Gary Lewis]

Yes, well done!  And on Jim's part as well.