Headlight/taillight/rear signal issue - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

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post #1 of 4 (permalink) Old 04-13-2013, 03:58 PM Thread Starter
Join Date: May 2011
Location: DC
Posts: 20
Headlight/taillight/rear signal issue

Lighting issues, here's what happens

Headlights off, left signals work but dim, right signal works normal, brake lights work but lift side is dim.

Headlights on, left signal doesn't work at all, right signal works normal, brake lights work but seem that the left side is always in "brake" mode.

I didn't check to see what the front signals are doing, but when the head lights are on the left signal indicator doesn't even come on.

What's wrong with this left side?

Thanks in advance

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post #2 of 4 (permalink) Old 04-13-2013, 05:25 PM
Join Date: Jan 2006
Posts: 12,381
Bad grounds!

Big Dave
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post #3 of 4 (permalink) Old 04-13-2013, 07:42 PM Thread Starter
Join Date: May 2011
Location: DC
Posts: 20
Big Dave...bad grounds on the left side tail lights?
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post #4 of 4 (permalink) Old 04-13-2013, 11:28 PM
Join Date: Jan 2006
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Yes every lamp has it's own individual ground path. There is one wire going to the lamp providing voltage and amperage to power the bulb, the chassis is the return or ground path.

The brightness of a bulb is a reflection of the voltage the bulb sees since the bulb is in itself only a resister. If you add more resistance by way of corrosion also called a bad ground then the voltage drop is going to be higher so the bulb glows dimmer.

I take a 10 gauge wire and run power from the back of my alternator directly to a solenoid to feed power to the head lights that is allowed to go to ground. The wire that would normally energizing the headlights instead energize the solenoid coil throwing the switch that completes the circuit (provided there isn't any corrosion where the bulbs go to ground; so follow the second wire out of the head lamp that ends in a ring terminal screwed into your sheet metal).

The bulbs see maximum voltage off the alternator which will crank up the output of the alternator as a load is placed upon it provided you are reving the motor up enough to provide the required power. Which is another reason I do not use a SI alternator and use the more modern CS or even newer one wire alternator to replace it.

With your blinker or turn signal every break in the wire that has a terminal is a source for corrosion and must be disassembled and cleaned. There is also a couple of grounding wires under the dash which do nothing more than ground different circuits (radio, lighting, turn signals, blower motor, etc.) to allow the switches to work.

Circuits are incredibly easy on paper, but a royal pain in the tush in reality, because it is so labor intensive to unwrap and disassemble everything to check and clean up all of the connections. It is infinitely easier to pay $250 to $270 for all new wiring and install it just once than to chase electrical gremlins and repair the old factory wiring.

I used to rip all of the factory circuits out as a mater of principle and replaced the wiring with heavier gauge wiring from Painless in all of my street cars / race cars.

Big Dave
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