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After replacing the harness in my 73 Mach 1 3 times and none of them work right, I've decided to build a new one from a wiring diagram and new wires and parts. Has anyone done this that would be willing to give some advice and any recommendations on the supplies?
 

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Exactly what problems are you having? Building a harness for a 71-3 is not exactly an easy task, no are many of the parts available. Three harnesses with problems tells me there is more to it than just your harnesses....
 
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Well, here is the list. And it varies by harness.

Dash lights don't work or don't work correctly, they either don't come on or only come on when the dimmer switch turns to bright. But if I run a hardwire from the light switch to the instrument cluster they will work. Horn works but won't work from the steering wheel. The fan on the heater doesn't work unless I run a hardwire to the switch. I have a short somewhere in the current one because I get a dead battery in a couple of days if I leave it hooked up. But despite pulling the entire harness and checking it, I can't find it. Interior lights don't work at all. Grill turn signal lights don't work at all either. Oil pressure guage doesn't work. But I put a different guage on it and the sending unit is working. Parking lights and headlights work. The car has fresh 351C 4V with CC heads. I'm using a Mallory uni-lite distributor with a regular coil. The car starts fairly easily and will run ok.
 

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Well, lets see:

Dash lights: most likely the rheostat on the headlight switch is very dirty. Either clean it or replace your headlight switch. 71-3 Stangs have crappy dashlights anyway, so get used to that.

Horn: If you can remove the center pad, cross the two terminals on the steering wheel hub, if the horn operates, then you have a problem with the switch in the center pad.

Fan: check all your fuses, etc. The fan on Fords can be finicky, especially if the switch is old.

Short: Take your positive cable off, and put a test light in between it and the positive terminal fo the battery. If it lights, then you do indeed have a draw. Have someone watch the light as you pull one fuse at a time from the fuse box. If the light goes out, you have found the circuit the short is located on. If it doesn't, then it is located somewhere in the headlight or tail light circuit, as they are run off a circuit breaker.

Grille Lights: these lamp holders are notorious for corrosion, check them carefully, and that the grounds are intact on the radiator support. A test light would be very handy here as well.

Oil pressure gauge: check the harness and connections on the engine. This little harness is available new, and often suffers from age and abuse. Check continuity from the sender to your gauge.
 
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Well, lets see:

Dash lights: most likely the rheostat on the headlight switch is very dirty. Either clean it or replace your headlight switch. 71-3 Stangs have crappy dashlights anyway, so get used to that.
Already replaced the switch. Still have that problem. I don't mind the crappy dashlights, but I would like to have some.

Horn: If you can remove the center pad, cross the two terminals on the steering wheel hub, if the horn operates, then you have a problem with the switch in the center pad.
I've tried this with no success. The pad isn't any good anyway. Just one more thing I have to replace, but the horn won't blow shorted across either. Gotta be in the harness.
Fan: check all your fuses, etc. The fan on Fords can be finicky, especially if the switch is old.
Done this as well. Too many times. The switch is old and may be a problem anyway. The bad part is I may have more than one problem. Harder to diagnose.
Short: Take your positive cable off, and put a test light in between it and the positive terminal fo the battery. If it lights, then you do indeed have a draw. Have someone watch the light as you pull one fuse at a time from the fuse box. If the light goes out, you have found the circuit the short is located on. If it doesn't, then it is located somewhere in the headlight or tail light circuit, as they are run off a circuit breaker.
Never thought of this. Thanks for the tip. I'll see what happens...
Grille Lights: these lamp holders are notorious for corrosion, check them carefully, and that the grounds are intact on the radiator support. A test light would be very handy here as well.
I have replaced them before and they were working. But of course the parts were used and may no longer be working. The wiring seems to be OK coming through the firewall, since I've used a test light to check.
Oil pressure gauge: check the harness and connections on the engine. This little harness is available new, and often suffers from age and abuse. Check continuity from the sender to your gauge.
I have the new harness, but I haven't put it in. I've been trying to chase down the other issues. Especially the short. I will give it some more time to see if I can salvage this harness. I certainly don't relish the thought of "rolling my own".

Thanks for the help.
 
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