69 Fuel Gauge: Install constant 5v Jump to Latest

[Nuzzlet 0]

I have a centroid fuel gauge sending unit. The manual tells me I need to power my stock fuel gauge with constant 5 volt power instead of the pulsing 5 volts from the factory. I have an automotive 12v to 5v converter, I'm just not sure what wires to splice into to make it work. I've been unable to find a wiring diagram. Does anybody have any ideas? 

 

Note I have a tach. Thank you! :)

[Midlife 814]

You need to splice into any ACC main power line.  Look for a black/green thick wire near the ignition switch, or use the fuse buss extender off of the fuse box (it is the diagonal piece on the fuse box).  Not all cars came with the buss extender, but WCCC and I can provide you one if your car doesn't have it.

[Nuzzlet 0]

1 minute ago, Midlife said:

You need to splice into any ACC main power line.  Look for a black/green thick wire near the ignition switch, or use the fuse buss extender off of the fuse box (it is the diagonal piece on the fuse box).  Not all cars came with the buss extender, but WCCC and I can provide you one if your car doesn't have it.

Thank you for the quick response! I've heard there are constant voltage regulators that snap into a 9v battery terminal? I can't seem to find that on my 69 on the cluster. Is it just for the older years? The black/green wire near the ingition switch is the 5 volt pulsed power? I have a 12 volt ignition wiring already spliced for the radio, I was going to use that to power my 12 to 5v constant converter.

[Midlife 814]

The CVR that snaps into a 9V battery terminal is not constant voltage, but is switching voltage quick enough to fool old-style gauges.  It's on the back of the dash cluster, center section.  That's not what you want.  Some catalogs sell true 5V steady voltage regulators; if you can find them, go for it as it is plug-n-play even for the old style gauges.  Yes, your 12V ignition for the radio is good enough for the gauge as well.

[Nuzzlet 0]

Just now, Midlife said:

The CVR that snaps into a 9V battery terminal is not constant voltage, but is switching voltage quick enough to fool old-style gauges.  It's on the back of the dash cluster, center section.  That's not what you want.  Some catalogs sell true 5V steady voltage regulators; if you can find them, go for it as it is plug-n-play even for the old style gauges.  Yes, your 12V ignition for the radio is good enough for the gauge as well.

Right, so the fuel gauge needs constant voltage. So in this case the best solution is to find a constant 5 volt regulator that snaps into that ones place that way I don't mess with the original wiring? What do you mean it isn't what i want? 

[aslanefe 333]

25 minutes ago, Nuzzlet said:

Right, so the fuel gauge needs constant voltage. So in this case the best solution is to find a constant 5 volt regulator that snaps into that ones place that way I don't mess with the original wiring? What do you mean it isn't what i want? 

If you need 12 volts for your 12 to 5v converter, "it is not what you want" is you can't get 12 v for your converter from the 9v battery terminal behind the dash cluster.

But if you can find the true 5v steady voltage regulator that snaps to 9v battery terminal, you can plug it behind cluster and not need to use your 12 to 5v converter.

I believe this is what Midlife's post says.

[Midlife 814]

The factory CVR is a switching voltage supply, and that is not what you want.  If you can find a CVR that is electronic and non-switching, and it is designed to replace the factory CVR, then it will be plug-n-play and no wiring modifications would be needed.  If you do need to modify the wires, then you need to modify the circuit card as well, as it supplies voltage to the fuel gauge and receives the fuel sending unit signal, so you'll need to tap into that signal as well. 

[Nuzzlet 0]

1 hour ago, Midlife said:

The factory CVR is a switching voltage supply, and that is not what you want.  If you can find a CVR that is electronic and non-switching, and it is designed to replace the factory CVR, then it will be plug-n-play and no wiring modifications would be needed.  If you do need to modify the wires, then you need to modify the circuit card as well, as it supplies voltage to the fuel gauge and receives the fuel sending unit signal, so you'll need to tap into that signal as well. 

 

2 hours ago, aslanefe said:

If you need 12 volts for your 12 to 5v converter, "it is not what you want" is you can't get 12 v for your converter from the 9v battery terminal behind the dash cluster.

But if you can find the true 5v steady voltage regulator that snaps to 9v battery terminal, you can plug it behind cluster and not need to use your 12 to 5v converter.

I believe this is what Midlife's post says.

Ahh, I believe I understand. Ill do a little looking on the cluster and see what I think. I also just ordered this. Seems like exactly what I am looking for.

[aslanefe 333]

48 minutes ago, Nuzzlet said:

 

Ahh, I believe I understand. Ill do a little looking on the cluster and see what I think. I also just ordered this. Seems like exactly what I am looking for.

If you remove the cluster, the voltage regulator and 9v battery terminal is next to speedo cable input as far as I remember. The link you posted does not work, but I assume it is one of those solid state (electronic, not bimetallic) voltage regulators that are available from quite a few vendors and you can replace your original regulator with that and get constant 5v needed for your sender then keep the 12 to 5v converter for an other project.

[Nuzzlet 0]

Just now, aslanefe said:

If you remove the cluster, the voltage regulator and 9v battery terminal is next to speedo cable input as far as I remember. The link you posted does not work, but I assume it is one of those solid state (electronic, not bimetallic) voltage regulators that are available from quite a few vendors and you can replace your original regulator with that and get constant 5v needed for your sender then keep the 12 to 5v converter for an other project.

Link should be fixed: https://www.cjponyparts.com/constant-voltage-regulator-1969-1973/p/HW1567/

That is what is is, and the 12 to 5 volt regulator I have is actually quite beefy so i will probably end up using it for LED strips, which was actually my original use for it before I discovered an answer to my fuel gauge problem. Thank you for the help, and i'll keep the forum posted when it arrives Friday.

[Mach1 Driver 560]

If you intend to use a 7805 regulator as the Centroid instructions indicate, this Word attachment should answer most of your questions.  I'd be interested to see how this capacitance type sender works for you.

CENTROID FUEL SENDER.doc

[Nuzzlet 0]

5 minutes ago, Mach1 Driver said:

If you intend to use a 7805 regulator as the Centroid instructions indicate, this Word attachment should answer most of your questions.  I'd be interested to see how this capacitance type sender works for you.

CENTROID FUEL SENDER.doc 44.5 kB · 1 download

Where did you find this? Thank you! 

Actually I've found a CVR that snaps into the 9 volt terminal on the cluster. But previously I was hoping to use a converter I have laying around, not the 7805. They will be arriving Friday so I'll let you know what happens. Ultimately if I have to buy a new sender I will but this came with the car so I mind as well use it.

[Mach1 Driver 560]

40 minutes ago, Nuzzlet said:

Where did you find this? Thank you! 

Actually I've found a CVR that snaps into the 9 volt terminal on the cluster. But previously I was hoping to use a converter I have laying around, not the 7805. They will be arriving Friday so I'll let you know what happens. Ultimately if I have to buy a new sender I will but this came with the car so I mind as well use it.

I made the schematic previously (the entire 5 pages are on this site under " How To's", A Real Schematic). I added the Centroid information from their website while I was on phone hold this AM. I had nothing better to do while waiting.  Let us know how well it registers fuel level.

[Nuzzlet 0]

40 minutes ago, Mach1 Driver said:

I made the schematic previously (the entire 5 pages are on this site under " How To's", A Real Schematic). I added the Centroid information from their website while I was on phone hold this AM. I had nothing better to do while waiting.  Let us know how well it registers fuel level.

According to centroid, the sender needs 12 volts, not the regulated 5 volts. I will let you know.

[Mach1 Driver 560]

Huh, well what I drew is from their website and for a 65-70 Mustang- if you are using a 76/6 ohm centroid sender. I just redrew it to show how to connect it to fuse #2 for power. What I read is that this new sender needs a constant 5v and that must be regulated down from a 12v source. As everyone has been telling you, the stock gauge voltage regulator is a mechanical device- it is a bi-metal that heats up to open and close and gives around 5v over time. That doesn't bother the gauges because they are dampened and react slowly. This can be seen if you have a full tank and turn on the key- it takes some time for the gauge to read full in a stock system.

[Nuzzlet 0]

6 minutes ago, Mach1 Driver said:

Huh, well what I drew is from their website and for a 65-70 Mustang- if you are using a 76/6 ohm centroid sender. I just redrew it to show how to connect it to fuse #2 for power.

Were you using this datasheet: http://www.centroidproducts.com/mustang.pdf? It shows the sender getting 12 volts from the fuse before the 7805 regulator. Either way I am also going to try the 9v battery terminal regulator I got here: https://www.cjponyparts.com/constant-voltage-regulator-1969-1973/p/HW1567/.

[Mach1 Driver 560]

You are partially correct. The Radio Shack terminal strip has four vertical strips. For instance, the Vign tap goes to the bottom right screw. That is connected only to the top right screw that goes to the fuse. That is likewise true for the other three strips. What you see in my drawing is a schematic for centroids drawing for which you have a link above. The 7805 regulator takes 12v and converts it to a regulated 5v. Trust me my friend- I'm an electrical engineer. The 12v is applied to the sender (as you stated) and that powers-up the sender and makes it operate. It will then send the proper signal out the "send neg" terminal to drive the fuel gauge. Does that make more sense ?

[Nuzzlet 0]

1 minute ago, Mach1 Driver said:

You are partially correct. The Radio Shack terminal strip has four vertical strips. For instance, the Vign tap goes to the bottom right screw. That is connected only to the top right screw that goes to the fuse. That is likewise true for the other three strips. What you see in my drawing is a schematic for centroids drawing for which you have a link above. The 7805 regulator takes 12v and converts it to a regulated 5v. Trust me my friend- I'm an electrical engineer. The 12v is applied to the sender (as you stated) and that powers-up the sender and makes it operate. It will then send the proper signal out the "send neg" terminal to drive the fuel gauge. Does that make more sense ?

Yes, so 12 volts from the battery going to the sender is ok? I believe that is how it is wired now. And then it should work when I put all the gauges to constant 5 volts.

[Mach1 Driver 560]

Yes 12v is needed to power-up the sender, as is the 5v from the 7805 regulator. The Centroid sender is an electronic device that uses capacitance to sense fuel level, instead of a float moving a rheostat on the stock fuel sender.. Then the Centroid sender mimics the stock sender and provides the correct resistance to ground for the fuel gauge. That is partly why the Centroid sender has a ground connection. Don't try to hook the Centroid sender up withot the 5v regulator in the circuit or you will probably fry something. Do the complete circuit they show (and is in my drawing as well). Any other questions?

[Nuzzlet 0]

8 minutes ago, Mach1 Driver said:

Yes 12v is needed to power-up the sender, as is the 5v from the 7805 regulator. The Centroid sender is an electronic device that uses capacitance to sense fuel level, instead of a float moving a rheostat on the stock fuel sender.. Then the Centroid sender mimics the stock sender and provides the correct resistance to ground for the fuel gauge. That is partly why the Centroid sender has a ground connection. Don't try to hook the Centroid sender up withot the 5v regulator in the circuit or you will probably fry something. Do the complete circuit they show (and is in my drawing as well). Any other questions?

I was hoping for a simpler solution than what they show. I have a 12 to 5v regulator from Amazon. But then I discovered they make the battery terminal one, do you think there will be a problem with that one? Also it's been connected for years as is using the pulsing 5 volts to the sender. You are suggesting I don't power it on while it's not connected to the send on the gauge and the gauge doesn't have 5 volts or else I'll fry somthing? 

 

And no, thank you so much for your time. I appreciate you shedding some electrical knowledge when I simply lack the skill and experience. You've answered more than enough questions. Just wanna make sure nothing blows up.

[Mach1 Driver 560]

34 minutes ago, Nuzzlet said:

1.  I discovered they make the battery terminal one, do you think there will be a problem with that one?

2. Also it's been connected for years as is using the pulsing 5 volts to the sender.

3.You are suggesting I don't power it on while it's not connected to the send on the gauge and the gauge doesn't have 5 volts or else I'll fry somthing? 

4. Just wanna make sure nothing blows up.

1. If it clips on and outputs a constant regulated 5v, then that is fine. It will power fuel, oil and water which is ok.

2. I'm not sure what you are saying there.

3. No, just that you need to complete the circuit as they wish. You will be doing that with the clip on regulator (if it outputs a constant 5v), and there is no need to add a 7805 (its probably already in in the clip on regulator)

4. That's OK, I understand and we have the same apprehension. Its just easier for me to find it and fix it if I screw-up.

I followed the link on the clip on regulator and that looks fine. I would still get the 12v from the same source as the clip on regulator- it is on in "Accy" and "On". That can be had at fuse #2 as I show. Its not good practice to power up the two sides of the circuit at different times.

[aslanefe 333]

If I understand it correctly, he needs to install the solid state 12 to 5 v regulator he got from CJ Pony instead of the original regulator behind the cluster, and also provide 12 volts and ground to his centroid sender (getting the 12v from a source which is powered with key ACC and On positions like the fuse box buss extender or radio power); am I right Mach1 Driver?

[Mach1 Driver 560]

53 minutes ago, aslanefe said:

If I understand it correctly, he needs to install the solid state 12 to 5 v regulator he got from CJ Pony instead of the original regulator behind the cluster, and also provide 12 volts and ground to his centroid sender (getting the 12v from a source which is powered with key ACC and On positions like the fuse box buss extender or radio power); am I right Mach1 Driver?

yep, that would do it

[Midlife 814]

Wow....that sending unit sure adds complexity to a standard Mustang.  Now one has to route a 12V (fused) line and a ground, along with the standard sending unit line back to the fuel tank.  That means pulling the rear seat, sides and door sill to route those wires back along with the standard tail-light.  OK, the ground can be fashioned entirely at the rear.  Now then, can the standard circuit card be used?  I think so.  Not entirely what I would do myself, just to get a better fuel gauge. 

I presume the gauge itself is now different, which means it probably is not compatible with the circuit card in a physical sense?  Or is the sending unit 6/76 ohms close enough to fit the Ford gauge? 

[Mach1 Driver 560]

Hi Mid. My read on this is that the gauge remains stock- they don't sell a replacement, and there are instructions to calibrate the sender for full and empty. I'm curious how accurate it will be- it seems the capacitance of the fuel changes from tank to tank so it is recalibrated automatically at full. I would guess you don't want to leave the fuel in there for a long time. Adding Stabil will probably do something to the level reading. It has my interest, but there are some unknowns here.