Here are the three originals in the front and the later behind them



I know crappy picture but here is one old layed on top of one new, identical in size



Is this a shunt resistor?


I dont care for this as I dont like things that get this hot. I have thought about just finding me a 12 volt motor to switch out with the 6 in my blower so I can get rid of this thing.

I bought this one on e-bay.....where can I get a shunt resistor locally, maybe radio shack?

I need to see if you stated what size I need to ask for

Maybe this one will be better

 

Thanks for finding those for me but when it all added up I was in for them too much so a member here sold me an entire assy, I didnt care whether the gauges that were in it worked or not.

I am going to pitch them unless someone here wants them?

 

Quote....... If I found the right one it is shown as 1.05 to 1.15 ohms in the 81 wiring diagrams......So it sounds like this shunt resistor can be found in an original eighty anything F-truck wiring harness?

That would be great, any clues on what to look for or where to look would be very helpful

 

Wilkapedia.........In electronics, a shunt is a device which allows electric current to pass around another point in the circuit by creating a low resistance path.

I was able to find this thread ...... https://www.ford-trucks.com/forums/6...hunt-wire.html and first post says ......One of the gauges is an ammeter, and requires a shunt wire between the alternator battery connection and the battery connector on the starter solenoid.

I guess I had better wait for a better explanation before I confuse myself worse

Maybe you are referring to the resistance wire that we already talked about which yes I am going to install?

I dont remember anyone using the word Shunt resistor though when we were working on that.

Nope I looked back and it was described as .........Also, you should know that there is an 8 - 10 ohm in-line resistor............

Again will shut up now and wait for someone to explain to me what I need and how I need it

 

A shunt resistor is one which takes the majority of the current, but in doing so creates a voltage across it which a smaller gauge can read.

I just ran a test on four different ammeters that I have, and found that it takes from .102 to .156 volts to show full scale. With that information we can calculate the required resistance to give us the proper voltage. If we use .125 volts as the typical value that shows full scale, and if we want full scale to be at 60 amps of current being pulled off the system:

 

Here is the way that I planned to wire these gauges which I believe you guys approved of.......

Now where in this do I need to put the shunt resistor and hopefully I can find one on one of these scrapyard trucks if I know where to look

 

Yes, you found a description of the shunt. Here's how it is wired:


But, since our meter is centered when there is no current it can read in either direction. Our "ammeter" is nothing but a very low voltage voltmeter, with full scale in either direction taking about .125 volt.

As for where to get a shunt resistor, I'm not sure. Since I was way wrong about the 1.05 ohms of that shunt when it should be more like .002 ohms you aren't going to be able to measure it. My meters won't read to much less than 1 ohm, so it isn't likely you'll have something that will let you measure things and determine which is the shunt. Maybe someone else will know.

 

Thanks, maybe something will come to mind on your end, in the meantime .....

 

Yes, that's how you wire the three amigos, but the ammeter is different. If you draw the battery at the bottom of my diagram and put the alternator and load at the top you'd have it. When the engine isn't running, or the alternator isn't working, then you'd have current flowing as the arrows show and the ammeter would register a discharge. When the engine is running, and the alternator is working, then any charging of the battery will show up as a charge on the ammeter. And, when everything is balanced, meaning that the alternator is carrying the load the meter will be at zero.

 

I have decided to start with this sending unit Interesting for me whats in there.

I cut off the bottom portion thinking I could use the original ring



New sending unit fits down in there just fine and it gives me the little bit of height that I may be after but I still just miss the holes.



Better this way anyway, I need access to bottom ring for installation/removal, I will trim the new sending unit a bit around its outer circumference and maybe weld something on bottom ring to take up the needed meat for screws.

Report back in an hour or so

 

Ran into a little bit of a snafu in that the sending unit rods were not as close as I first thought in that the original has a bend away and back toward the end.

Looking at my tank I can see that the front side bottom is curved, I think this may be the resistance I felt that I had mentioned in an earlier post. I though that possibly the new sending unit was a bit longer when in fact it is a bit shorter.

I bent my unit to match old float to get it away from that curve on the face of that tank.

I am also glad that I took the time to fit old cut off sending unit top onto the fuel tank otherwise I would not have known that it only goes one way if you want the screws to line up in their original holes.

So placed it on there and marked where it needs to sit everytime and noted the position of the direction the sending unit needed to be pointing everytime and now I am sorta back to square one.

I am thinking that now that I know the rod/float assy is a bit shorter than original I am not going to want to raise it up off the tank any more than may be necessary unless I am confused?

I think I will go out there and place sending unit in tank now without said adapter and see how it feels and maybe re-think things if necessary.

Any input is appreciated

 

Any chance of swapping the arms? Or, of cutting and brazing? But, the fact that the new one is shorter than the old does mean that you don't want to raise the new one much or you'll go to Empty way early - which is better than late.

 

Now that I have had a few minutes to think about it I think that a shorter sending uinit ( within reason we are talking less than an inch too be sure ) would only give me an empty reading sooner, is that correct.

If so I can definitely live with that!

 

Exactly what I was thinking, I considered swapping arms but the old one is made from heavier gauge so without major modification of sending unit ( I.E I screwed it up ) I think I better stay clear of that.

I know little about soldering and can braze with a coat hanger but thats as far as I have ever experienced. I dont think I will want to mig it ( which would not be an issue for me )

I like your idea of going empty (on the gauge ) a little bit early.

I guess I will need to re-think my adapter to lower it as much as possible.

Back to the drawing board

 

I may be wrong in my reasoning but when I place the sending unit down into the tank without adapter it will still sit 3/4 of an inch above the tank until I get the float over on its way to the drivers side a bit.

I am going to guess that they give a little bit of Oh my god I better get to the gas station quick time before it starts sucking fumes so I think that I may still be ok on the reading even with a 1/2 high adapter.

Only speculation of course or is that wishful thinking