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Mike S.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 7081
Experience:  ASE Certified Master Technician
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My rear turn signal does not work. The bulb is good and l

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My rear turn signal does not work. The bulb is good and l have checked the fuse, it is good also
JA: Most vehicles have two fuse panels. Have you located both?
Customer: Yes I checked under the hood and on both sides of the dash panel. This issue is with a 04 Chevy classic
JA: Are you fixing your Classic yourself? What have you tried so far?
Customer: Yes . I have pulled the circuit board and replaced it as it was bad because from water damage
JA: Anything else you want the mechanic to know before I connect you?
Customer: I have had issues with the tail lamps many time in the past and have fixed the issues but this one has got me puzzled. I have tested the connecting power plug with a test light and am getting power but it flashes really fast like it would if there was a burned out bulb

Hi, I am Mike, welcome. I'm reviewing your question.

Do the front turn signals work?

Then tell me if the turn signal indicators on the instrument cluster work?

I see you are viewing my questions but you are not replying back. I will just give you the wiring diagram then get back to me if you have any questions for me.

Customer: replied 2 months ago.
the right signal in the front works but flashes very fast like it would with a burned out bulb, also the same on the instrument cluster.

Are you saying just one rear turn signal is out cause you didn't say right or left just rear. So, which is out?

Customer: replied 2 months ago.
just the right rear
Customer: replied 2 months ago.
The left side works as it properly
Customer: replied 2 months ago.
Left side works fine

Ok, using a voltmeter or at least a 12 volt test light see if you are getting a voltage on the wire feeding that right rear turn signal bulb, so remove the bulb and test the prongs in the socket. Make sure you turn the key to run and put on the right turn signal.

It's the dark blue wire.

Customer: replied 2 months ago.
Already done that and I was getting power and was getting a fast flashing just like the front signal

Ok, then it has got to be a ground problem.

The ground is G402 and is located on the right side of rear package shelf.

Find the ground, undo it and clean the metal with a wire brush or sandpaper, re-attach the ground, make sure it is tight and check the turn signal again.

But the taillamps and stop lamps on that side are also grounded there so if they work ok, perhaps it's not the ground.

Do the tail lamps and stop lamps on the right rear work ok?

Customer: replied 2 months ago.
Tail lamps are working but brake lamps aren't

Is there a circuit board in that rear taillamp assembly? Is that what you replaced before?

Is there voltage on the wire for the stop lamps? If so and it's low, it sounds as though the 2 wires are shorted together.

Or the circuit board is shorted.

Customer: replied 2 months ago.
Just replaced the circuit board today
Customer: replied 2 months ago.
I will check the voltage on the brake light .

Ok, can you tell me if the circuit board would be upstream or downstream from testing those 2 wires?

Is there voltage on the wire for the stop lamps? If so and it's low?

Customer: replied 2 months ago.
Can you clarify what you mean up and down stream?

Meaning coming from the turn signal switch, which comes first where the wire goes to the bulb or the circuit board. In other words does that voltage have to pass through the circuit board before it gets to the bulb?

The wiring diagram doesnt' even show me a circuit board there.

Customer: replied 2 months ago.
When I was checking for voltage with a test light at the turn signal wire (blue) I probed the plug from the wire harness that connect to the circuit board that all 4 bulbs plug into

Ok, have you checked the voltage on the stop lamp wire yet?

Customer: replied 2 months ago.
No not yet...Can I get back with you later on that

That's fine.

Customer: replied 2 months ago.
OK Mike...Thank you for your time and letting me pick your brain

If and when you test that stop lamp light blue wire and it's below battery voltage, I believe then that that wire is short circuited to that turn signal dark blue wire somewhere. It appears that it cannot be too far from the rear though because they soon separate before heading forward.

Get the voltage yet?

Find the short yet?

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