Instrument voltage regulator polarity

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My search abilities probably missed the answer, but I was wondering what the polarity of the IVR is as I wanted to check mine to confirm output. In other words is the small connector positive and the large one negative as one finds on a 9 volt battery?

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When looking at the back, and the ground lug below, the input power is on the right; the output power is on the left.
 
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Greetings Midlife! With your description of the CVR/IVR polarity I decided to see if the schematics I have might be of any use, or if I needed to annotate them provide needed verification in the PDF file(s) I have. Well, I could not tell the polarity of the CVR/IVR from the schematics, so I decided to clarify which terminal on the CVR/IVR had what polarity. But, before I lock it down I thought I ought to run this by you to make certain I got it right, or if I need to alter my little graphic representation of your verbal description.

Did I get it correctly?

Thank you.

1649334041582.png
 
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Not quite. The IVR is a primitive voltage reducer. It takes B+ (battery voltage) and creates a pulsing low (6V+) voltage to power the gauges. Your drawing should have 'IGN' on the male snap connector (your +) and 'ACC' on the female connector (your -). The mounting tab is the electrical ground.
 

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Not quite. The IVR is a primitive voltage reducer. It takes B+ (battery voltage) and creates a pulsing low (6V+) voltage to power the gauges. Your drawing should have 'IGN' on the male snap connector (your +) and 'ACC' on the female connector (your -). The mounting tab is the electrical ground.
I wouldn't use the term "ACC" when describing the CVR output as ACC typically refers to Accessory (switched) power. For the CVR, the actual input is ACC reduced by a 10 ohm resistor wire (not ignition) and the purpose of the resistor wire is to slow the response of the gauges when powering them up.
 
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When looking at the back, and the ground lug below, the input power is on the right; the output power is on the left.
By back, do you mean the back of it as it is inserted in the dash cluster or the side with the snaps that match those on a 9 volt battery? I realize the spacing is different, but the snap connectors are the same size.

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I wouldn't use the term "ACC" when describing the CVR output as ACC typically refers to Accessory (switched) power. For the CVR, the actual input is ACC reduced by a 10 ohm resistor wire (not ignition) and the purpose of the resistor wire is to slow the response of the gauges when powering them up.
Yeah, I thought of that after, but that's the way some were marked from Ford. I've only seen them on the older fiberboard backed ones, the later plastic board are IGN only or nothing.
Male and Female are consistent until 2010 or so, then they started 'self identifying'... ;)
 
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Not quite. The IVR is a primitive voltage reducer. It takes B+ (battery voltage) and creates a pulsing low (6V+) voltage to power the gauges. Your drawing should have 'IGN' on the male snap connector (your +) and 'ACC' on the female connector (your -). The mounting tab is the electrical ground.
Awesome clarification, from The Man himself. Okay, I can't help it. All Hail RocketMan!

Seriously. Yeah, I am being playfully serious... I, for one, appreciate what he has done for our hobby.
 
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I have digested all the foregoing posts, and have revised/enhanced the prior IVR drawing as follows. With any luck I am hopeful I interpreted everybody's linguistics accurately. If so I will update my PDF snippet for 1973 (and earlier) Instrumentation Circuitry accordingly. Many thanks for the considerate comments. They have all been helpful.

1649426046805.png


The info re: 5 VDC is from the 1973 Shop Manual from Forel Publications:
1649426297353.png
 
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I have digested all the foregoing posts, and have revised/enhanced the prior IVR drawing as follows. With any luck I am hopeful I interpreted everybody's linguistics accurately. If so I will update my PDF snippet for 1973 (and earlier) Instrumentation Circuitry accordingly. Many thanks for the considerate comments. They have all been helpful.

Outstanding and thanks to everyone. I am now confident of a lack of explosions when testing the silly thing. It is enough of a PITA to get to that I wanted to be sure it was kosher before putting it back together!
 
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Just to make sure that everyone is on the same page, here is how the connections are for the IVR, for both with and without gauges.
View attachment 62171
Many thanks, Don, for the photo and added clarifications. I will added the annotated photo to my documentation on the subject, and updated/corrected my graphic representation accordingly, both as seen below. We can't get much more clear that that!

It has been many years since I have worked as a technician (later-mid 70s through earlier 80s at a Ford dealership in SoCal), and my even earlier years learning all I could about automotive repair at a local community college while working on several different vehicles I owned and drove back then (2 were 1969 Mustangs). Running through this thread, and digging up and enhancing my documentation and schematics, brought back a lot of very fond memories. I loved working as a tech back in the day, despite my involvement being largely during the frustrating initial years when Muscle Cars began their descent into the Gasoline Shortage and Emission Control instigated performance hell that brought out ever lower, even depressing, levels of performance. Finally, many years later, technology finally began to fulfill the promise of "potentially" better fuel milage (our 2020 GT500 not withstanding), lower emissions, and higher performance. It was during the first few years of performance darkness in the earlier part of the 80s that the Siren Song of white collar corporate America, and soon after the computer industry, lured me into a different (but related) direction.

Once I was retired over 30 years later (medical issues forced my retirement, brain cancer, I am now an 8 year survivor) I returned to my "real roots," and I am relentlessly loving it. Lynda and I have two really nice 1973 Mustangs (a Mach 1 & a "True Survivor" Convertible), and a 1969 Shelby GT500 to work on, tinker with, play in, drive, and take to car shows. We also have a 2020 Shelby GT500 for an older vs newer comparison between the two GT500s! Further, to help me maintain the excellent running experience of the vintage pony cars I have a "relatively advanced" Sun Oscilloscope (the kind with inductive leads for the Ignition Coil and Cylinder #1 ignition cables), and one of the venerable Sun VAT-40 diagnostic/testing machines (VAT - Volt Amperage Tester). I made a good living using that kind of Sun equipment, and am so happy I was able to scrounge these pieces of yesteryear together, in working condition no less. When I work on those old ponies I am 19 again.

Have I mentioned to anyone lately how much I love and enjoy this hobby? Much less being able to participate as much as I do. If I could do more, I would... I do what I can, and am grateful and happy for that.

1649469567865.png


Annotated photograph of a typical IVR. Note the Ground Lug is in an upward position as opposed to the graphic depiction shown immediately above.
1649469621186.png
 

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Just to make sure that everyone is on the same page, here is how the connections are for the IVR, for both with and without gauges.
View attachment 62171

Don, thanks so much! Now, even I won't have an excuse for starting an electrical fire!
 
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Nice equipment, mrghmhale, keep hoping I come across a Sun oscilloscope. The other thing I would like is a distributor machine/tester, Allen or Sun. I figure I could make one using a variable speed drill. I have enough other electronic test equipment to at least be able to map the curve.

Too many other little projects keep interrupting me. Wife and I bought a used motorhome a couple of months ago, nice condition just needed some TLC. We've had 11 motorhomes and 5 camp trailers in the last 47 years, so we know how we like them set up, just one more small thing and I'll be able to get back on the Mustang. Weather is getting better, which means we'll be spending time at the campgrounds along the coast, too.
 
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Nice equipment, mrghmhale, keep hoping I come across a Sun oscilloscope. The other thing I would like is a distributor machine/tester, Allen or Sun. I figure I could make one using a variable speed drill. I have enough other electronic test equipment to at least be able to map the curve.

Too many other little projects keep interrupting me. Wife and I bought a used motorhome a couple of months ago, nice condition just needed some TLC. We've had 11 motorhomes and 5 camp trailers in the last 47 years, so we know how we like them set up, just one more small thing and I'll be able to get back on the Mustang. Weather is getting better, which means we'll be spending time at the campgrounds along the coast, too.
Ah, yes, a Sun distributor machine. That would be nice, But, sadly enough I am so tight on space in my home garage, even after expanding it to a 3 car garage a few years ago. I would have made it a 3 1/2 car wide garage, but the slope on the side of the house where I added the third car garage stall was not going to cooperate with that kind of alteration. I took what I could get, and am happy enough with it.

Check out this Group on Facebook. You may be able to locate an old Sun scope there.
"Vintage Sun Service Equipment"
 
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Just to make sure that everyone is on the same page, here is how the connections are for the IVR, for both with and without gauges.
View attachment 62171
Thank you for the deeper clarification I will add that tidbit to my documentation also. I also re-re-re-edited my post above with the graphic and photo images of the IVR and related circuitry. While making the changes to enhance clarification I also included the relevant circuit numbers, just in case anyone needed the circuit # information when digging through the schematics on those circuits.
 
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Ah, yes, a Sun distributor machine. That would be nice, But, sadly enough I am so tight on space in my home garage, even after expanding it to a 3 car garage a few years ago. I would have made it a 3 1/2 car wide garage, but the slope on the side of the house where I added the third car garage stall was not going to cooperate with that kind of alteration. I took what I could get, and am happy enough with it.

Check out this Group on Facebook. You may be able to locate an old Sun scope there.
"Vintage Sun Service Equipment"
Thanks for the link, but we gave up on Facebook several years ago. I'll keep checking Craigslist. My oldest son came up with a dual trace oscilloscope and a function generator a few years ago for next to nothing, maybe I'll luck out, too.

I know what you mean about space (or lack thereof). We downsized a couple of years ago, workshop went from 24' by 30' feet to 18' by 24'. At least the 2 car garage stores all of the non automotive stuff, like wood working and gardening.
 
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Don, thanks so much! Now, even I won't have an excuse for starting an electrical fire!

Just gone done putting it on a voltmeter for the 5v output. Boy, it does fluctuate. I am using an LED readout and probably was not seeing the top of the swing, but the closest it got to 5v was a bit over 4V. Does that sound about right? The swings were so fast I don't think I would have much faith in reading it well enough to adjust. If my results sound doubtful, probably best to put in a new one.

Thanks in advance.
 
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