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Old 06-25-2004, 07:46 PM   #1
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Where is your Tach "Illumination" wire hooked to?

On my truck, I have the Tach's Illumination wire hooked into the headlight switch up in the dash. But everytime I turn on my headlights, my tach goes semi-crazy. It looks like it's idling 500rpm higher, but as soon as I turn OFF the lights, the tach reads fine. Any ideas?
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Old 06-25-2004, 08:05 PM   #2
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All my gauges are hooked up to the instrument light circuit. Gray wires.
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Old 06-25-2004, 08:29 PM   #3
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Quote:
Originally Posted by swervin ervin
All my gauges are hooked up to the instrument light circuit. Gray wires.
Where's that located? On the fuse block, or....
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Old 06-25-2004, 08:31 PM   #4
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It's in the wiring harness that plugs into the back of the cluster.
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Old 06-25-2004, 08:32 PM   #5
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Quote:
Originally Posted by gldevall
It's in the wiring harness that plugs into the back of the cluster.
Hmm, and it's a GRAY wire huh? I'll go out and look for it right now then...
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Old 06-25-2004, 09:01 PM   #6
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If you don't have the stock stereo than look for a gray wire by the stereo (It used to have a dash light in it) and run it from that wire. That is what I accidentally soldered a wire to when installing my deck
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Old 06-25-2004, 09:38 PM   #7
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Well, as hard as it may sound..I actually found the "Gray" wire first shot. Hopefully, tonight, the tach won't bounce around when I turn on the headlights.
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Old 07-07-2004, 07:59 PM   #8
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My fuse block has a "lmps" (or something like that) socket in it. Plug it in there.
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Old 07-07-2004, 08:19 PM   #9
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Tach is hooked up to instrument lights, when they go on so does the tach.
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Old 07-08-2004, 09:54 AM   #10
86-C10-V6
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Sounds like you have a bad ground

Appling power to the lights on the tach should have no impact on the tach reading, if it does I think you have a bad ground going to the tach.
There is a special fuse on the fuse block for the instrument lamps that is powered from the light switch, I believe it has a 5 amp fuse, you should be able to connect either to the gray wire as Swervin indicated or to the fuse block.
Hope this helps.
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