Electrical system has a mind of its own...

Question

1988-1998 Chevrolet Pickup

Formally called the Chevrolet C/K, C/K is a series of trucks manufactured by General Motors and marketed under the Chevrolet and GMC brands. The C/K line includes pickup trucks, medium-duty, and heavy trucks.

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Michael A @michaela64575

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crwdns2931729:0crwdne2931729:0: yesterdayHuk 3, 2025

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Electrical system has a mind of its own...

So I got my Truck back from having the bed replaced after it was hit while parked and the electrical system is all mucked up. It was already having little things here and there before but now its just a total mess. My break lights work fine during the day but when I turn my headlights on the break lights dont work at all. Also all the time when I push down on the breaks the display for changing the air from hot to cold turns off until I take my foot off the break. That also blinks rabidly when I use my turn signal as well. Lastly the right speaker makes buzzing noises here and there which I thought maybe the speaker is dying but that could be connected to the whole electrical mess. Anyway just asking around to before biting the bullet and spending money at a repair shop. Thanks!

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@michaela64575 check the wiring harness running underneath the bed. Make sure there are no shorts to ground (chassis) and that the connector is properly seated. See if disconnecting the harness resolves most of these "the display for changing the air from hot to cold turns off until I take my foot off the break. That also blinks rabidly when I use my turn signal as well" issues.

crwdns2934271:0yesterdayHuk 3, 2025crwdnd2934271:0 oldturkey03 crwdne2934271:0

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@michaela64575 check the wiring harness running underneath the bed. Make sure there are no shorts to ground (chassis) and that the connector is properly seated. See if disconnecting the harness resolves most of these "the display for changing the air from hot to cold turns off until I take my foot off the break. That also blinks rabidly when I use my turn signal as well" issues. — oldturkey03

score 0 · Answer 1 · 2025-11-03T21:26:38-07:00

BRAKE is not break. Obviously, everything is broken, Buzzing sound in a speaker means the speaker is working. The buzz is coming from the radio. If the buzz is being injected into the radio because of bad wiring or filters, it would buzz in stereo. Otherwise, it is likely a radio problem. But it may be introduced into that speaker wire, considering everything else seems to be mis-wired.

Your BRAKE lights are colocated with tail lights. If u turn headlights on, your tail lights should light. Sounds like u are saying nothing back there works.

If this truck has an ECU, that would be the first suspect. I can't imagine any mis-wiring that would affect the display and cause the brake function u are describing.

The tail light bulb has 2 inputs (or there is 2 bulbs) and one ground. headlight power supplies one input. Braking supplies the other input.

Dash lights are also turned on with headlights. Pressing the brake pedal grounds the brake sensor line. All of these are separate circuits, which is why I am going with an ECU issue, and it may just be a bad connection or ground on the ECU.

1988-1998 Chevrolet Pickup

Electrical system has a mind of its own...

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