Radio flashes with turn signal

In my 1996 K2500 I’m having trouble with turn signals and tail lights. The driver side works fine but the passenger side brake light does not work, and the radio flashes with the turn signal. When the headlights are on the passenger side doesn’t work at all.

I inspected all the wiring I can see up front that may have been damaged from the core support replacement but everything looks fine. I also inspected the trailer harness and it looks good to go. I noticed a ground wire that was cut and self tapped into the bed but I don’t see where it tied into as the harness looks totally stock and unmolested.

I saw an old post that someone said it could be the small corner marker sockets being bad. But idk what that means especially if those turn markers appear to work fine up front.

If you're getting back-feed power like that, grounds are compromised. That "self-tapped" ground out back is where I'd start.

Your radio and taillights are on separate grounds, but go ahead and ensure they're clean and tight. How do your battery cables look?

Yes they're on separate grounds, but if the tail light grounds are bad, the blinkers will back feed the park lights circuit which causes the dash illumination.

Any ideas as to why my voltmeter (on the dash) jumps in concert with the turn signals (both sides) and hazards? Didn't used to - only started today.

You sure it didn't used to? Mine always did before I went LED-everything... In every truck I've had.

AK49BWL said:

You sure it didn't used to? Mine always did before I went LED-everything... In every truck I've had.

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No, not entirely! Just noticed it yesterday and maybe it has been doing it all along. Anyone (everyone!) else's truck doing the same thing?

Pinger said:

Any ideas as to why my voltmeter (on the dash) jumps in concert with the turn signals (both sides) and hazards? Didn't used to - only started today.

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Depends on how many accessories are on. AC,or heater, radio, CD player, lights, it may be drawing enough to do this. In those situations, my trucks do it, but as long as the battery is charging and they start okay, I'm not too worried.

Pinger said:

No, not entirely! Just noticed it yesterday and maybe it has been doing it all along. Anyone (everyone!) else's truck doing the same thing?

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My '94 does it, especially at idle. It's quite pronounced, actually.

I suppose a stronger alternator than stock (and upgraded wiring) would help some, no?

c

HotWheelsBurban said:

Depends on how many accessories are on. AC,or heater, radio, CD player, lights, it may be drawing enough to do this. In those situations, my trucks do it, but as long as the battery is charging and they start okay, I'm not too worried.

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It does it with nothing else switched on - with or without engine running - and I'm pretty sure it didn't before. The audio warning 'seems' louder also - though I could be imagining that. All that I'd noticed prior to this was the voltmeter fluttering at the point of engine shutdown as its needle dropped back on the scale. That, I've only noticed in the past few weeks but could have been doing it forever.

Truck was in for its annual safety inspection on Tuesday and when I got it back it was doing this. Hard to believe anything in the inspection caused it - but hard to ignore the timing. It did - during the test for no obvious reason - get left sitting idling with headlamps switched on for some 10-15 minutes.