Wire ID

[jscott]

Was looking at pictures of Mustang engine bays and noticed that I did not see this wire on any of the pictures I looked at.   This fairly thick wire from the top area of the starter solenoid to the dash, running thru the firewall  on the drivers side.  I cannot get under the dash right now to see where it goes (If I can)  as I threw my back out but what would this wire be for?   

 I am also trying to figure out the correct replacement harness for my alternator, my car originally did not have a tach or gauges but does not so not sure if the prior owner changed the harness or has the original one.  I see NPD lists two for the 1972 Mustang, one without gauge package and one with but they also say there are 5 different versions of this harness.  Guess I will take my current one out to compare.  I do not run the amp gauge any longer in the center pod, have a Bosch volt meter now in  place.

https://www.npdlink.com/product/wire-loom-alternator-to-voltage-regulator-there-are/102025/202878

https://www.npdlink.com/product/wire-loom-alternator-to-voltage-regulator-there-are/102026/202878

 

[Hemikiller]

That's the auxiliary power feed for options like power windows, power seat (Cougar), rear window defroster, power top (convertible only) and the automatic seat back latches. The wire terminates under the dash with a yellow plug that accepts up to three male bullet connectors. It traverses the engine compartment from the battery (+) post on the starter solenoid, over the shock tower, down the length of the passenger side shock tower brace and then across the firewall, over the driver side shock tower brace and to the grommet in the firewall. 

Warning light and gage harnesses are easy to tell apart. Warning light harnesses only have one Black w/orange stripe wire, it comes from the alternator harness to the solenoid. Gage pack cars will have one from the alternator harness, and one from the vehicle main harness. 

Alternator harness on a warning light car has all four positions of the regulator plug filled, gage cars only use three. 

 

[cv_72mustang]

Hi I just did mine last week using the NPD part without the gauges.  My car is the 72 vert  and had auxiliary power feed but did not impact my new harness.   I did exactly what you mentioned.  I took old harness out and traced the wires to the connectors on the vreg and alternator and doubled checked with schematic.  The  new harness matched the terminal posts sizes on the alternator and regulator and starter relay.  I was concerned about busting the terminals off my original alternator and used a little PB blaster so loosen them up a bit.  The colors of wires didn't match up but just rechecked where they go.   I also traced the new harness out before install.  I really didn't want to cause more issue since  it want to drive my car and not spend hours tracing a burnt alternator, harness or anything else.  The harness quality is good.  

If you need more you can PM me.  

Also, I managed to get the new harness on without pulling out  alternator.   

 

[jscott]

was able to get under the dash today and that wire is indeed going to the yellow three hole plug, behind the kick panel on the driver side..  Only one wire coming out of it and it goes up the driver side of the car into the dash.  If it is indeed for seat release or something I guess I can pull it but really not sure................

 

[midlife]

The convenience group harness uses that plug in exactly the manner as shown above.  The other uses are power windows, power convertible tops, and rear defrosters.

 

[jscott]

The convenience group harness uses that plug in exactly the manner as shown above.  The other uses are power windows, power convertible tops, and rear defrosters.

What did the convenience group consist of?

 

[midlife]

Things like: seat back release, map lamp, emergency brake light, etc.

 

[jscott]

Things like: seat back release, map lamp, emergency brake light, etc.

if those are the possible items is there any reason this wire cannot run off of the acc terminal on the fuse box instead of running thru the engine bay to the starter solenoid? 

 

[midlife]

Yes: those items demand more power than the ACC fuse can handle.  That's why it runs directly off of the battery with a circuit breaker.

 

[jscott]

guess I will leave it....can I splice in some additional same gauge wire to give it a little length to clean up the engine bay?

 

[midlife]

Sure. Be careful that it doesn't drop down onto the headers.  Protect your splices as well!

 

[jscott]

Things like: seat back release, map lamp, emergency brake light, etc.

the map light and emergency brake light (same as parking brake?) take lots of power?  I never would have thought that, I have led bulbs in both of those now.

 

[midlife]

Map light no; it gets its power from courtesy light circuit.  That power lead is primarily for the seat back release.  E-brake light gets its power from ACC fuse buss bar/3prong plug.

 

[jscott]

so I am guessing that my one wire out from the triple yellow plug may go nowhere as those plugs under the seat are not connected........or could they have been for seat belts??   There is a plug coming from the floor pan to under the seat and then a plug from the bottom of the seat, nothing was connect when I got it and when I put in insulation with new carpet I just sort of buried the plug that comes from the floor pan under the insulation.

 

[midlife]

That I do not know.  I infer what the function of many accessory items without knowing the details of each model year.

 

[libram]

midlife infers with an extremely educated guess, always. From experience there was some fast and loose play going on at the ford plant in the early 70's. If it fit and worked but had an extra wire so what....or maybe you would upgrade to that package down the line and on the other end of it, ford execs has specific parts made just for these cars.....that got cancelled from mass production in 1973 so we have to fit pinto parts or truck parts, or just make our own, at least a few years ago getting seat mounts was damn near impossible for some model, and some parts are just an almost interchangeable replacement that were close bc thats what the execs decided were better and cheaper. 

These cars are a lot lot depression era harleys, if "Tim" put it together he had 16 of the old model bearings to use and he finished those in march, but maybe Mark put it together and he had 24 of those bearings but he was slow so he didnt start using the new ones until october so which one is it ? lol

 

[jscott]

I had to move the car before I began some engine bay work.  I pulled the 1 wire plugged into the yellow triple plug, did not notice anything not working.  So can I just remove the wire from the starter solenoid and from the  ar completely?   Want to keep the engine bay as clean of wires as possible

 

[midlife]

If there is a wire plugged into the yellow triple plug, it must be there for a reason.  However, it will not affect the basic functionality of the car.  I'd follow that wire and find where it goes (most likely a 3 prong plug that mates to a relay).