Wiring question re: Instrument panel

jim7485 · Oct 22, 2004

I am in the middle of installing the Painless wiring kit on my 66 stang, which is giving me some PAIN. On the back of the insrument cluster, there are 8 'posts' for the wiring on 4 different guages. The kit says to put the black/green wires on the 'I' posts and the various other colors on the 'S' posts. The posts are not marked, of course. Even if you are not using Painless, do you know if there is a difference between the posts, and how do I tell which ones to use?

Thanks
jim-

WORTH · Oct 23, 2004

jim7485 said:
I am in the middle of installing the Painless wiring kit on my 66 stang, which is giving me some PAIN. On the back of the insrument cluster, there are 8 'posts' for the wiring on 4 different guages. The kit says to put the black/green wires on the 'I' posts and the various other colors on the 'S' posts. The posts are not marked, of course. Even if you are not using Painless, do you know if there is a difference between the posts, and how do I tell which ones to use?

Thanks
jim-

The guage is sensing current from the sender, in theory it wouldn't matter if you ran the current in the wrong direction. It has to be insulated from ground, so it wont short regardless of which way you wire it. I don't think it's going to matter.

limey66 · Oct 23, 2004

WORTH said:
The guage is sensing current from the sender, in theory it wouldn't matter if you ran the current in the wrong direction. It has to be insulated from ground, so it wont short regardless of which way you wire it. I don't think it's going to matter.

Wrong I'm afraid.

If you wire it back to front, the needle on the gauge will try to wrap itself round the 'zero' stop...

As for a solution to your problem, I'm sure someone here has the answer...guys?

limey66 · Oct 23, 2004

Just thought I'd reasearch this one a little for you - I couldn't use mine as a reference as the previous owner wired EVERYTHING in black/yellow...!

Anyway, go here here for a pic:

http://www.hammar.dyndns.org/~djhamma/wiring/1966/66instr.jpg

This shows the black/green going to the left post of each gauge (with the cluster face down on your lap if you're in the driver's seat). Whatever the colour of the wiring, the feed from the voltage regulator on the back of the cluster needs to go to the left post of each gauge.

Hope this helps.

WORTH · Oct 24, 2004

limey66 said:
Wrong I'm afraid.

If you wire it back to front, the needle on the gauge will try to wrap itself round the 'zero' stop...

As for a solution to your problem, I'm sure someone here has the answer...guys?

Have you actually tryed this? 2 reasons I ask, #1 if it's reading resistance it shouldn't matter how it's hooked up, and #2 if it was polarity contious I would think Ford would have used different terminals so you couldn't hook it up backwards.

limey66 · Oct 24, 2004

OK WORTH, here comes the science bit...

Lets take a fuel gauge as an example, like you say it 'reads' resistance (which changes as the float goes up and down in the tank). The way it reads resistance is by starting with a nominal 12V from the battery, running through the resistance that could be zero Ohms when the tank is full so we get all our 12V at the gauge or as the tank gets empty, say 5 ohms which means we get less than our 12V at the gauge. Most gauges are what are referred to moving coil meters, which means there's a little coil of copper wire attached to the needle and a permanent magnet (or another coil) fixed to the meter body. As current flows through the coil fixed to the needle, a magnetic field is produced that repels the one from the magnet or stationary coil and moves the needle. Clever, eh? Now, the magnetic field around a wire is always clockwise with regard to current direction - it's called the right hand grip rule. Make a fist with your right hand and stick out your thumb, as if thumbing for a lift (like when you run out of gas, 'cause your gauge is wired backwards... ), the direction your thumb is pointing is the current in the wire, your fingers represent the direction of the circular magnetic field around the wire. Now point your thumb the other way like we got the wires on the wrong terminals and you can see the magnetic field goes the other way.

A bit long winded explaining that, but that's how basic electrical theory works.

WORTH · Oct 24, 2004

limey66 said:
OK WORTH, here comes the science bit...

Lets take a fuel gauge as an example, like you say it 'reads' resistance (which changes as the float goes up and down in the tank). The way it reads resistance is by starting with a nominal 12V from the battery, running through the resistance that could be zero Ohms when the tank is full so we get all our 12V at the gauge or as the tank gets empty, say 5 ohms which means we get less than our 12V at the gauge. Most gauges are what are referred to moving coil meters, which means there's a little coil of copper wire attached to the needle and a permanent magnet (or another coil) fixed to the meter body. As current flows through the coil fixed to the needle, a magnetic field is produced that repels the one from the magnet or stationary coil and moves the needle. Clever, eh? Now, the magnetic field around a wire is always clockwise with regard to current direction - it's called the right hand grip rule. Make a fist with your right hand and stick out your thumb, as if thumbing for a lift (like when you run out of gas, 'cause your gauge is wired backwards... ), the direction your thumb is pointing is the current in the wire, your fingers represent the direction of the circular magnetic field around the wire. Now point your thumb the other way like we got the wires on the wrong terminals and you can see the magnetic field goes the other way.

A bit long winded explaining that, but that's how basic electrical theory works.

So your saying if you run the coil with a left handed winding it wont creat a magnetic field? or will it reverse the polarity of the field?

limey66 · Oct 24, 2004

If you run the current the other way through the wire (a coil is just a lot of wires looped together to get a greater magnetic field) you get the magnetic field going the other way, so it moves the needle the other way.

WORTH · Oct 24, 2004

limey66 said:
If you run the current the other way through the wire (a coil is just a lot of wires looped together to get a greater magnetic field) you get the magnetic field going the other way, so it moves the needle the other way.

So I can make a North and a South electromagnet by wiring one backwards? Cool.

Hack · Oct 24, 2004

WORTH said:
So I can make a North and a South electromagnet by wiring one backwards? Cool.

Every magnet has both south and north poles. If you've seen a drawing of field lines around a magnet, they originate at one tip of the magnet and end at the other tip. Those are the magnetic poles. A link below.

http://theory.uwinnipeg.ca/mod_tech/node92.html

If you send the current through an electromagnet the opposite way, the polarity will reverse. North becomes south and vicey versy

pabear89 · Oct 24, 2004

WORTH said:
Have you actually tryed this? 2 reasons I ask, #1 if it's reading resistance it shouldn't matter how it's hooked up, and #2 if it was polarity contious I would think Ford would have used different terminals so you couldn't hook it up backwards.

1. It does matter on how it reads they will register backwards.
2. Cost from factory stand point, the Wiring harness on the dash guages have the left side is a short lead tapped into the Low voltage reg for the guages. the right side is always to the sending unit that reads resistence to Ground.
The dash speedo pod is wired before it goes into the car,
At another assy point.

WORTH · Oct 27, 2004

limey66 said:
If you run the current the other way through the wire (a coil is just a lot of wires looped together to get a greater magnetic field) you get the magnetic field going the other way, so it moves the needle the other way.

OK Limey, I just blew a Small Hole in your theory. I have my instrument panel out of my 46 pickup. I had to check the guages to make sure they worked so I hooked up my DC variable power supply to them, all 3 guages, FUEL,TEMP,OIL PRESSURE work the same wired pos-neg or neg-pos. ANd they are acurate to the same voltage, no difference in needle possition at the same voltage, pos or neg.

limey66 · Oct 27, 2004

OK WORTH, firstly it's not MY theory, a guy by the name of Fleming (amongst others) had a lot to do with it. It's accepted electrical knowledge and is even taught in the US.

I guess what is happening is that you have nice expensive instruments (the type I mentioned with two coils, rather than a coil and a permanent magnet). The first (fixed) coil produces a magnetic field for the second (moving coil) to repel against; reverse the polarity and you are producing the magnetic field in both coils the other way round, so it works fine. If you got cheaper gauges with a permanent magnet THE NEEDLE WILL GO THE OTHER WAY.

I don't know what type of gauge is fitted to classic 'stangs because I've never stripped one down that far, but the aim of this forum is to advise people and anyone else reading the thread the best course of action. If none of us actually KNOW what's going to happen if he wires it backwards then we gotta go back to first principles and think it through.

65mistress · Oct 27, 2004

Jim7485 - How's the installation going? I've been looking at that kit, but I didn't really like the look of the wiring, maybe it's my lack of electrical knowledge, but the wires looked like they were wrapped in paper.

How has the install gone so far?

WORTH · Oct 28, 2004

limey66 said:
OK WORTH, firstly it's not MY theory, a guy by the name of Fleming (amongst others) had a lot to do with it. It's accepted electrical knowledge and is even taught in the US.

I guess what is happening is that you have nice expensive instruments (the type I mentioned with two coils, rather than a coil and a permanent magnet). The first (fixed) coil produces a magnetic field for the second (moving coil) to repel against; reverse the polarity and you are producing the magnetic field in both coils the other way round, so it works fine. If you got cheaper gauges with a permanent magnet THE NEEDLE WILL GO THE OTHER WAY.

I don't know what type of gauge is fitted to classic 'stangs because I've never stripped one down that far, but the aim of this forum is to advise people and anyone else reading the thread the best course of action. If none of us actually KNOW what's going to happen if he wires it backwards then we gotta go back to first principles and think it through.

AH, Limey, perhaps you got up on the wrong side of the bed today, but my post was not a peronal attack, nor was it ment to offend you, I was merely supplying the results of my little test. I did not go in search of destroying your little theory. Our conversation got me thinking about the Guages in my '46 project so I figured it would be a good way to test your theory out.

It's very possible the Prince of Darkness has a different way of making guages than the American companies do.

Not everyone here exclusively owns Mustangs. So the knowledge gained here is not restricted to 10 years of Mustangs. And not all classics have the exstensive knowledge available to Mustang enthusiests. So a little background information can't hurt.

Good Day Sir.

limey66 · Oct 29, 2004

Aha, the good ol' Prince of Darkness...

Just re-read my reply above and yeah maybe I did sound a bit narked. Sorry 'bout that. I have the gauges out on my Mustang at the moment and I'm making the two hour drive to work on her this weekend, so I'll give them a check too. (Just for interest).

Broke the diff on my daily driver this morning.

Keep it real, or whatever it is the Vdub guys say.

WORTH · Oct 29, 2004

limey66 said:
Aha, the good ol' Prince of Darkness...

Just re-read my reply above and yeah maybe I did sound a bit narked. Sorry 'bout that. I have the gauges out on my Mustang at the moment and I'm making the two hour drive to work on her this weekend, so I'll give them a check too. (Just for interest).

Broke the diff on my daily driver this morning.

Keep it real, or whatever it is the Vdub guys say.

No problem , let me know if the mustang guages are the same.

limey66 · Oct 30, 2004

OK, so I have the gauges on my lap, I connect my dc supply to the temp gauge the correct way round, all is OK. I swapped the polarity......and......dammit the bloody thing worked correctly!

I told it in no uncertain terms that it obviously didn't know what it was doing...

It should read backwards, but it doesn't. Nuts.

I think that just about confirms it WORTH, I'll shuddup now.

WORTH · Oct 30, 2004

limey66 said:
OK, so I have the gauges on my lap, I connect my dc supply to the temp gauge the correct way round, all is OK. I swapped the polarity......and......dammit the bloody thing worked correctly!

I told it in no uncertain terms that it obviously didn't know what it was doing...

It should read backwards, but it doesn't. Nuts.

I think that just about confirms it WORTH, I'll shuddup now.

I told you, you shouldn't listen to the Prince of Darkness

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