Can anyone help me identify these two wires?

I tried the Serv Manual schematics but wow it is tough to decipher.

One wire is brown (I think) and covered in a stainless steel shielding or sleeve in addition to the coloured wire insulation itself. It travels along the firewall and enters the car between the brake booster and fender. Inside it seems to pass by the guages and terminate somewhere (by feel) behind the heater controls or that area anyway.

Could it be the rear defogger power wire?? Or is this a wire for the coil as it seems to have suficient length to reach it??

See Pic #1

In Pic #2 I have located two wires that are attached to one terminal and I think they go to the coil but I am not sure. Is one the ignition wire and the other the tach wire??

Do these go to the POS terminal of the coil??

 

the shielded wire looks to be the original tach wire. the one with the two looks like the original ignition wire to the coil. it looks like you have an MSD distributor? if so did you install it? if not and the car runs someone ran a new ignition wire to feed it 12 volts as the original is a resistor wire.

 

The only shielded wire I know of in these cars is the radio antenna wire.
Any chance it could be that?

Those look like the coil wires to me. One is the IGN+ wire (ballast resistor wire unless it has been changed) and the other is the ballast resistor override wire that goes to the starter solenoid.
The tach wire would be separate.
And, yes, they do go to the + terminal of the coil.

- Eric

 

Thx guys!

The car hasnt run yet since I installed the motor. I installed the MSD and I am just trying to make sure all the connections are correct.

Eric - As for antenna wire, I'm not sure. Its a small wire - not typically what I'm used to like in my Grand Nat'l. It is shielded tho, but where is the antenna? I dont have one mounted on the car anywhere....at this point I'm praying its the tach wire!!

 

The antenna wire is thick, like you'd expect.

If original, it would be expected to go through the firewall in the center, just under the windshield (has two small screws that hold a bracket to the firewall, if I recall), from the inside side. The antenna is in the windshield.

Sounds like it's the tach wire. Having never had an OEM tach, I had not known that the original wire is shielded.

- Eric

 

mine is a 70 model and yes the tach wire is shielded and the center wire is brown. the shield is grounded I assume to keep the tach from causing radio interference.

 

Okay great lads thx again.

So then I can hook the tach wire directly up to the MSD distributor tach wire only and it doesnt need to go to the coil?

 

I think so...

 

what MSD are you using? if it is something like a 6A or other that has a separate box with a dedicated tach connection then I think you need a tach adapter from MSD. the MSD uses a different signal than the original GM tach's that ran from the coil. you could probably hook it to the coil and it should work but you may want to check with tech service at MSD.

 

Its an MSD Pro-Billet PN 8529. (Olds model)

Just a distributor - not a 6a box etc. Has a simple hook up to the pos and neg terminals of the coil plus a gnd. The MSD has a gry tach wire coming from it. I'm hoping it works okay. If not I'll hook it to the coil.

If it goes to the coil then to which terminal?

 

Negative - the one that gets interrupted.

The positive terminal is just 12VDC.

- Eric

 

Thx.

Ill let you guys know how it goes!

 

Eric,

The factory tach wire was shielded. Bringing an ignition wire through the firewall into the dash area is a good way to create an audio tachometer with the radio unless you shield it.

 

Thanks, Joe - I've only had aftermarket tachs, and none of them ever used shielded wires.
Maybe they should have...

- Eric