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68' Help identifying this under dash wire.

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Old Apr 4, 2015 | 12:41 PM
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Default 68' Help identifying this under dash wire.

Help with identifying this underdash wire in my 68. This is a heavy gauge brown wire. It is coming from the leg of the wiring harness that services the ignition switch. I have replaced the ignition switch. The igition switch has seven poles/spades that the plug plugs into but only six seemed to be used. The spade that is empty is labeled ground. I know that igition switches may have been used in several different GM models. The igition switch does seem to work so far meaning the engine turns over. I don't know if this brown wire has anything to do with the ignition switch because the ground I assume would be a black wire and this wire in question is brown. Does anybody know where this heavy gauge brown wire goes and what it services? Thanks, Tom.
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Old Apr 4, 2015 | 07:59 PM
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It's been a few years since I replaced all the wiring in my 68 and I remember the brown 12 gauge wire plugged into a capacitor mounted to or near the back of the tach. It seems rather strange to have a powered wire do nothing but plug into a noise suppression capacitor.

Remember we're dealing with a 68 and they have more than a few one of a kinds!

Just pulled out the OH SO EZ wiring diagram and it's labeled Radio Capacitor Connector On Ignition Switch. It splits off of a brown 12 gauge wire that runs from the fuse block up to the ignition switch.

Last edited by 1Fordman; Apr 4, 2015 at 08:06 PM.
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Old Apr 5, 2015 | 09:35 AM
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Originally Posted by 1Fordman
It's been a few years since I replaced all the wiring in my 68 and I remember the brown 12 gauge wire plugged into a capacitor mounted to or near the back of the tach. It seems rather strange to have a powered wire do nothing but plug into a noise suppression capacitor.

Remember we're dealing with a 68 and they have more than a few one of a kinds!

Just pulled out the OH SO EZ wiring diagram and it's labeled Radio Capacitor Connector On Ignition Switch. It splits off of a brown 12 gauge wire that runs from the fuse block up to the ignition switch.
WOW Fordman..... I just reistalled my speedo/tach cluster last night!! And never thought to look back there. But that wire would reach to the back of the tach. I haven't replaced the gauge cluster yet. Maybe I can still look with a mirror and reach behind the tach. That may also explain why after 47 years it is not connected? Somewhere along the life cycle somebody removed this noise suppressor. Does that mean there are TWO radio noise supressors? One one the back of the gauge cluster and one on/or near the tach you are talking about??? Thanks Tom. I'll try to post a pic......
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Old Apr 5, 2015 | 09:46 AM
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Originally Posted by tomdoc
...Does that mean there are TWO radio noise supressors?...
There are more than two on cars equipped with factory radio equipment. UPC U-69 Sheets A3 and A4 in the AIM show them. You'll also want to flip over to Sheet A8 for the exhaust and body ground straps.

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