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Mach1 Driver

1970 Mustang Exterior Lights (turn signals)

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BSWOR you should consider pinning this post also. 

Since completing my 1969 Mach1 Schematic (see A REAL Schematic) I have seen a lot of confusion about 1970 turn and marker lights. I didn't know they were different than the 69, but they sounded interesting so I investigated to see if I wanted to upgrade. After reviewing the circuit I decided to leave well enough alone, but hopefully the attached three pages will help explain their operation for those poor souls with 70s ;) 

1970 MUSTANG EXTERIOR LIGHTS PAGE 1.pdf

1970 MUSTANG EXTERIOR LIGHTS PAGE 2.pdf

 

1970 MUSTANG EXTERIOR LIGHTS PAGE 3.pdf

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An other great job, thanks a lot. Wonder why they changed the design for 70 ?  Do you see any advantages/increase in reliability etc between 69 and 70?

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Most companies are "Marketing" driven. Someone in engineering had a wet dream and came up with this wonderful new feature where the marker lights would flash alternately with the turn signals. I imagine it looks neat. And all they had to do was delete the ground on the marker lights and wire it into the flasher circuit. It just required some added wire, so it was easy to do. It looks like something I might of come up with in my yout.

Now, as I was sayin Your Honor, the down side is that it doesn't always alternately flash. If the headlights are OFF the marker lights flash in sequence with the turn signals. Aw but the exuberance of yout overlooks this minor drawback. I recently read a post on VMF where a guy in England (I think) started pulling his car apart trying to figure out what was wrong. And of course he got the usual "helpful" suggestions- until I told him it was normal operation. The marker lights are in series with anywhere form 3 to 10 other light bulbs depending on whether the headlights are on or off. If one of the 1157 bulbs burns out or looses its ground then it could take a while to figure out what went wrong. I find the circuit more than a little "screwy".

The movie above is of course "My Cousin Vinny" and ya gotta love Mona Lisa Vito's testimony- that girl knows her cars. 

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On 7/25/2017 at 8:38 PM, aslanefe said:

An other great job, thanks a lot. Wonder why they changed the design for 70 ?  Do you see any advantages/increase in reliability etc between 69 and 70?

To better answer your question, I refer you to our harness guru Midlife, who makes a business of actually restoring Mustang wire harnesses:

There are distinct differences between the 69 and 70 underdash harnesses, with the 69's being far superior in design/reliability. For the 64.5-8's, there's not much difference in functionality, except the 67/68's include as integral the wiper system, e-switch system and a separate dash cluster. For the 64.5-68's, much of the additional features were separate harnesses that plugged into the main underdash; these included A/C, consoles, courtesy lights, etc.
 
 

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On the 69's, the side lights were only running lights; on the 70's, it was a combination running lights and turn signals.  I wouldn't be at all surprised that there was a Federal mandate to have turn signals on the sides of vehicles for safety reasons.  The running lights were mandated in 1968.

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