Questions about vintage gauges

[DTraina]

Hi forum - I've been trying to wrap my (wiring-challenged) head around the vintage gauges. I have a fully-assembled Blueprint 302 and a Holley Sniper EFI. Here are my questions:

1. Battery Charge Indicator: The first step in the vintage gauge instructions says to "solder a 510 OHM resistor, found on the Mustang white gauge pod, between wires"...and I'll just stop right there because I'm already lost. If this step is necessary, can someone translate to English?
2. Tachometer: Do I connect the yellow wire from the Tachometer gauge directly to the neg (-) post on the coil?
3. Water Temp: Do I install the water temp sensor and then run that black cable directly to the water temp gauge? (skip the RF harness)
4. Oil Pressure: Do I install the oil temp sensor and then run that cable directly to the oil temp gauge? (skip the RF harness)
5. Fuel level: I need some help here. Where do the white and blacjk wires connect?

Appreciate any help! (keep it as simple and clear as you can - I'm a noob)

[Ted G]

This is a little confusing as I am at the same spot...... Watching

[edwardb]

Curious where you're seeing the "solder a 510 OHM resistor, found on the Mustang white gauge pod..." statement. I don't see it in my complete kit build manual or the latest RF chassis wiring instructions. Certainly not in the Speedhut (Vintage gauge brand) instructions. That's clearly a reference to a donor build using parts accordingly. I'm assuming you aren't doing a donor build? Or at the very least not using any Mustang donor gauge components? If so, ignore this instruction.

Your best bet for wiring is to use the instructions that came with your Vintage (Speedhut) gauges along with the latest version of the chassis wiring guide. Found here: https://www.factoryfive.com/wp-content/uploads/2021/11/Chassis-Harness-rev-W.pdf. The wiring information in the build manual, at least in my experience, is not detailed enough or maybe not even up-to-date compared to the other sources. You should find everything you need in the Speedhut instructions along with the RF chassis wiring guide.

Regarding whether to use the Speedhut (again, Vintage...) cables directly to the gauges or not is a build decision. Personally, I prefer to run them to the sending unit wires on the RF harness. Then connect the dash wiring harness to the gauges as shown in the instructions. That way all the connections to the dash go through the large RF dash connectors and the dash can be more easily disconnected. But others prefer to run them direct. It's your choice.

I get the "noob" comment. Wiring is often cited as the most difficult part of the build by many. It may seem intimidating. But if you take it a step at a time you can get through it. Study the above mentioned instructions carefully. The schematic in the RF chassis wiring guide is probably one of your biggest resources. For a beginner, it may seem overwhelming. But if you take the time to study and trace each circuit and wire, it should make sense. That plus the Speedhut instructions which I find to be well done. Good luck.

[rich grsc]

Hi forum - I've been trying to wrap my (wiring-challenged) head around the vintage gauges. I

1. Battery Charge Indicator: The first step in the vintage gauge instructions says to "solder a 510 OHM resistor, found on the Mustang white gauge pod, between wires"...and I'll just stop right there because I'm Appreciate any help! (keep it as simple and clear as you can - I'm a noob)


Not sure why you reading about using donor gauge sets out of a mustang, but you can completely disregard that whole section.
As Paul says, use the wire instruction that came with the gauges. Next, read the instructions,(I don't understand this), read again, (well maybe I get it), read again, (ok I think I understand), read at least one more time. Wiring isn't easy for a lot, myself included, but if I have to read it a dozen times, then thats what it takes.

[skidd]

If possible, please post what gauges and sensors you have. It helps to know if you are referencing electrical, or mechanical.

1. This 510ohm resistor depends on your alternator setup. See link 1 below: with instructions on using a 3G alternator in a 1G application. See the "No Run-On" section. You'll see a diagram with the indicator light and resistor. Also the image in link #2. This (I) wire is the "excite" wire to the alternator. It needs 12v power provided only when the key is on. "Power in Run" is often the term used. When the alternator is not yet "running", it provides a path for electricity to flow to ground inside the alternator, which in turn lights up your "indicator" bulb (if you have one). This power to the alternator is used to "excite" the field windings to get the alternator working as it starts to spin. Once the alternator is running, the excite wire no longer provides a grounded path for 12v, and your indicator bulb turns off. In fact, your alternator will start to provide 12v back on this wire, which is why some GM applications need a diode on this wire, fords do not. The 510 ohm resistor does a few things. It limits the current flowing into the alternator excite wire. It also provides a dedicated path for power to flow, if your "indicator" bulb burns out, or you don't have one. It also forces power into the indicator bulb if you happen to have one. This "forces" is simply due to the path-of-least-resistance. If you didn't have a resistor, your indicator light would never light up.
Cliff Notes: You'll need this resistor if you have an indicator light. And, even without an indicator light, it's a good idea to use a resistor to limit the current flow to the alternator. I have a dedicated indicator light on my dash, and obviously also a resistor soldered in as well.
https://www.motortrend.com/how-to/install-high-output-ford-3g-alternator-older-fords/
https://www.ffcars.com/threads/is-a-charge-light-needed-with-a-3g-alternator.554713/

2. In simple terms. Yes. Unless you have a unique setup like a CD box or something. But, yes. Tach signal is nearly always drawn from the negative terminal of the coil.
Over-simplified explanation: This is because the negative side is what your ignition box, or points are tied to. Before your plug fires, the points are closed, allowing full power into your coils primary winding. Your points open when it's time to "fire" the plug.. cutting off the flow of 12v into the primary winding... which collapses its electro-magnetic field, causing the secondary windings field to spike the voltage to thousands of volts, and down to your plug it goes through your rotor and cap.

3. Not familiar with the specific temp sensor you have. If it's a typical electric temp sensor, then yes, just run the wire back to your gauge. Doesn't matter if you use it's wire, or the RF wire spiced into that wire. If you for some reason are running an old-school mechanical water temp probe and gauge, then that's different. You have to use the wire with the sensor.

4. cable? Again, is this an electrical or mechanical sensor and gauge? Like #3, if its an electrical gauge, you can use any wire to run from the sensor back to the gauge. It's, or the RF wire. If it's mechanical.. again.. that's very different.

5. Which black and white wires? From the sending unit in the tank? Or.. wires on your gauges? Or the RF wires? If you're using a typical mustang tank and sending unit, the wires from it are typically black and yellow. Most of the time, it's a simple case of yellow-wire to gauge sensor input terminal/wire. Some gauges include a dedicated "ground" to connect to the black wire from the tank sensor. But, you can use "chassis" ground for that black wire also. So, if the "black-and-wire" wires are from your gauge, black-to-black, white-to-yellow.

[DTraina]

Thanks for the insights fellas. I was just as confused by the mustang donor gauge pod language as you are, but those are the instructions that FFR sends with the gauges, which are the FFR Electric Gauge Set (GPS) Part No. 16007. If you visit this site (https://www.factoryfiveparts.com/16007-factory-five-vintage-gauge-set-w-gps-speedometer/) and download the instructions, you'll see all of that Mustang gauge pod language.

But based on everyone's comments, it sounds like I'm OK to run the yellow tach wire direct to the coil (-), and run the water temp and oil pressure cables from the dash direct to the sensors in the engine. The speedo is GPS, so I've read that it's best to run the antenna to the far right (passenger) side and mount it on the chassis. The clock and volt gauge are easy. As for the fuel gauge - the set comes with a black cable but is it OK if I toss that and in this case just use the connection coming through the ron francis dash harness - light green "gas sender" (and ground) wires?

Let me know if I'm off anywhere. For the record, what threw me (in addition to the nutty gauge pod language in the instructions and a severe phobia of wiring) is that the gauge set comes with the water temp and oil pressure sensors that include their own cables/harnesses. It seems simple in retrospect (butt connect these to the wires in the RF sending unit harness), but at no point in the RF wiring or the gauge instructions does anyone bridge that gap for those of us who are electrically challenged.

[Papa]

Hi forum - I've been trying to wrap my (wiring-challenged) head around the vintage gauges. I have a fully-assembled Blueprint 302 and a Holley Sniper EFI. Here are my questions:

1. Battery Charge Indicator: The first step in the vintage gauge instructions says to "solder a 510 OHM resistor, found on the Mustang white gauge pod, between wires"...and I'll just stop right there because I'm already lost. If this step is necessary, can someone translate to English?
2. Tachometer: Do I connect the yellow wire from the Tachometer gauge directly to the neg (-) post on the coil?
3. Water Temp: Do I install the water temp sensor and then run that black cable directly to the water temp gauge? (skip the RF harness)
4. Oil Pressure: Do I install the oil temp sensor and then run that cable directly to the oil temp gauge? (skip the RF harness)
5. Fuel level: I need some help here. Where do the white and blacjk wires connect?

Appreciate any help! (keep it as simple and clear as you can - I'm a noob)

1. Any 12v switched power wire can be used to feed the volt meter gauge. I used the same power wire that powers the gauges from the Ron Francis (RF) harness
2. Yes, the simplest tach connection with the Holly Sniper is the coil (-) unless you are also using some sort of CDI ignition box, which will have its own tach signal output.
3. I recommend using the RF harness for the sensor connections whenever possible.
4. Same comment as #3
5. The RF harness has a leg for the fuel sender to the rear harness that gets connected to the sender in the fuel tank using the old-style Ford plug.

For the rest of the Holly Sniper connections, here is a post I did a while back: https://thefactoryfiveforum.com/showthread.php?31493-Connecting-Holley-Sniper-EFI-to-the-RF-Harness-advice-please&p=359724&viewfull=1#post359724

Dave

[DTraina]

Dave, your build thread has been invaluable, and the sniper wiring page you reference above is bookmarked in my browser. You, Edward, Rich and others - without you guys I would have given up a long time ago.

After my previous post, when I went back to work I decided to toss the tach wire that came with the gauge set and plug into the RF sender instead, connecting the purple wire to the coil (-). Seemed cleaner than introducing yet another wire to the rat's nest behind the dash. The other gauge leveraging the RF harness is the fuel, which is connected to the "gas sender" connector (light green + ground). The oil PSI and water temp are direct connects, bypassing the RF harness. Hopefully I've got it all hooked up right - will find out tomorrow when I start her up for the first time!!!