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Rear turn signal

Tiny
ALWYSWRKIN
  • MEMBER
  • 1990 GMC C1500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 194,000 MILES
When I use my turn signal to turn left I get the fast blink like a bulb is out. So I replaced it. All other bulbs are working fine. I cleaned the socket really good, put new electric contact grease and still nothing. It is not blowing the new bulb but the one that was in it was blow. Tried the hazards, same thing but no fast blink. Just not flashing.
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Monday, October 29th, 2018 AT 8:50 AM

11 Replies

Tiny
PATENTED_REPAIR_PRO
  • MECHANIC
  • 1,853 POSTS
This is confusing. You say it flashes fast but then again you say it does not even work. So what do you mean?
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Monday, October 29th, 2018 AT 9:56 AM
Tiny
ALWYSWRKIN
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  • 6 POSTS
Sorry, it does not work at all. Like a bad bulb. I have tried several new bulbs and nothing. Have you ever seen when it is the taillight assembly where the connector plugs in?
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Monday, October 29th, 2018 AT 10:38 AM
Tiny
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  • MECHANIC
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Use a voltmeter or at least a 12 volt test light and test in the empty bulb socket for voltage with the lights on. If there is no voltage, test the supply wire for voltage at the next accessible spot going back toward the turn signal switch. If there is voltage though, then check the ground wire for being loose, etc. It could be the taillight assembly if the empty socket has no voltage, but the wire just before the assembly has voltage.
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Monday, October 29th, 2018 AT 11:03 AM
Tiny
ALWYSWRKIN
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  • 6 POSTS
I tested every thing with a test light and it has power to the assembly. With a test light now. I cleaned and replaced the nut and bolt for the ground wire and I even removed the spaghetti mess trailer light harness that was spliced into the stock harness. So now it will not flash the bulb in the assembly but if I tap into the plug going into the assembly it will flash the test light but it is a fast flash. Passenger side everything is fine. Now why would it fast flash the test light?
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Monday, November 5th, 2018 AT 12:15 AM
Tiny
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  • MECHANIC
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Usually it will flash fast if something is shorted out cause. Since you are getting voltage to the taillight assembly it does sound like you are correct, the taillight assembly is at fault.
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+1
Monday, November 5th, 2018 AT 7:02 AM
Tiny
ALWYSWRKIN
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  • 6 POSTS
Thanks.
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Monday, November 5th, 2018 AT 9:05 AM
Tiny
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You are welcome!
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Monday, November 5th, 2018 AT 9:16 AM
Tiny
ALWYSWRKIN
  • MEMBER
  • 6 POSTS
I will get back to you with the results.
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Monday, November 5th, 2018 AT 9:25 AM
Tiny
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Okay, thank you.
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Monday, November 5th, 2018 AT 10:20 AM
Tiny
ALWYSWRKIN
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  • 6 POSTS
Sure enough, it was the circuit board. I included what was left of the metal contact tab that was attached to the curcuit. Looks like corrosion got to it until it eventually shorted out. I disassembled it to see what actually happened.
Thanks again
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Monday, November 5th, 2018 AT 11:27 PM
Tiny
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You are welcome.
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Tuesday, November 6th, 2018 AT 6:46 AM

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