1969 Repro Headlight Harness May be Incorrect

[Midlife 814]

A customer sent in a 69 non-tach headlight harness for refurbishment, but it was too far gone for me to repair.  The main power lines to/from the starter solenoid and alternator didn't look right to me, as the alternator line should go down into the harness quite a ways, and then gets spliced back into the main power feed.  This is the point where one of the ammeter lines gets its signal (yellow wire).  Instead, the yellow wire only was spliced into the main power feed, and the alternator line looped back and was spliced into the main power feed before going to the starter solenoid.

Whoever designed this created an epic failure of the ammeter, which now can only read discharge and never any charging.  (Not that they were all that functional anyway, but still...)

I do not know if this was an AMP harness or someone else who fabricated 69 headlight harnesses.  The next time I get a true AMP harness in, I'll tear it apart and see if they have this bad design or not.

[stangs-R-me 120]

Interesting !!

I've got an Alloy Metal non-tach Headlamp harness on my car that I purchased in 2005 / installed in 2011.   My Ammeter Gauge does not move as much as it did when I 1st bought the car in the early 80's, but I've swapped to nicer clusters a few times since then.   Current cluster has been in the car since the late 80's, and I don't think this particular Ammeter has ever had much movement before or after the new headlamp harness.   

Doug

[Mach1 Driver 560]

The amp meter (which is actually a galvanometer- because it registers + and -) works by shunting a small amount of current around a section of the main harness, wire 38A which is 22" long. A little bit or resistance and the ammeter doesn't work. That can happen at the firewall plug, at the connector to the flex circuit, at the meter, or all of the above. Mine hasn't worked in so long I can't remember if it ever worked. Below is a schematic for a 69 (not a wire diagram):

You could try cleaning up the connections with Brasso. As long as the ammeter is still good, that should get it back to normal. Personally I think the alternator warning light that's on the tach cars is a better indicator that the alternator is working.