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This vehicle runs great with no problems other than this.

All of the lighting including headlights, taillights, instrument panel, dome lights, etc., flicker.

That is, they go bright and dim at a quick rate of change. The flickering rate does not seem to change with acceleration, but it does seem less noticeable at highway speeds.

They have been doing this for over a year and I have not found the problem. I have cleaned the batery contacts, replaced a burnt battery connector, replaced the battery, looked for faulty ground straps (although I could have overlooked one somewhere). I have checked around the fuse box under the hood.

Is there a chassis ground strap somehwhere that I need to check?
Is my alternator faulty?


Any suggestions would be appreciated.

I bought this car used. I did not get to speak with the previous owner, but there had been transmission work done and the exhaust manifold had not been tightened, nor had the 4WD connector been properly connected. It is possible that the electrical problem was also introduced at this time.
 

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I have the same thing going on and I can't figure it out either. Talked to the dealership about it and since they couldn't see the problem in the day time they thought it would be pointless to troubleshoot it. Go figure.
 

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Assuming the supply and ground connections are good and only the lights flicker; typically, the common point of your problem is the headlight switch assembly. There's a lot going on there. I've had more than one car with a faulty instrument panel lamp dimmer (rheostat), they can overheat and do all sorts of naughty things. You didn't mention... do you have ANY auxiliary lighting that could be overloading the headlight switch? It could be something as unassuming as a bad dial light in an aftermarket radio.
To test, first take your headlight switch assembly out of the equation. Disassembly requirements may vary by model (you didn't specify) to unplug the switch. Test each circuit individually (the schematic will give you the color codes): jump from the plug to the switch and then from the plug past the switch. If you don't detect a switch problem with any of the individual lighting circuits, then start combining circuits. Hopefully, you'll soon learn learn if the switch is your problem.
Of course you could just plug in a new switch and see what happens.
Good luck.
 

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these are known for bad alts if you flicker when driving the battery should be out of the loop but i suspct a bad alt. put a volt meter on it and see what it is doing and the head light switch is another good spot for failure....mike
 

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My 84 Suburban did that. I cleaned up all the ground connections and added a ground cable from the motor to the chassis. It solved the problem.
 

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Make sure you have a 10 GA cable from the negative post of the battery to the body of the truck. This will happen if that connection is broken. (It should already have this connection, but it may be broken, corroded, etc.)
 

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I had the same kind of problem and this is what my truck was doing. When I was driving at night I had the headlights on and would turn the turn signal to make a turn. When I applied the brake the truck would just shut completely off as if the negative cable was taken off. I would stop the truck and start it again and it would be fine for a while and then do the same thing. I went through the entire truck checking ground straps but in the end it was a short where the trailer lights were. The owner before me removed the trailer lighting adapter and left the bare wire to short. You can also take your alternator into autozone or checker and have it tested. They hook it up to a belt and run a load on it and the end result is they tell you if it passes or fails. Often times the alternator will not fail as a whole. but the voltage regulator that is included in the alternator might. My suggestion if you havent done so yet is to get another alternator from checker and install it and see if that fixes the problem. If it does then you are good, if not return the alternator because they have a great return policy. I do not currently know if the load test they do in the store checks the voltage regulator as well. Does the truck ever have a dead battery when you try to start it? If the alterntor was not functioning properly you would have that problem as well. I would have to guess that you have a short somewhere which could be a complete nightmare. My short I could determine it was in the brake lights, but I dont know where it would be in your case. Also was the truck freshly painted? Sometimes although the ground straps are present they are not making a good connection due to paint covering the ground. It is pretty common these days so you might also want to look into that. Hope this helps! Let us know what conclusion you come to and if you figured out the problem.
 
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