Fuel sender ohms seem wrong

[Razorbackbronco]

So today installed a new 13 gallon steel main tank and a new 66-69 fuel sender unit. It says that it’s ohm range is 0-65. After putting in the tank I put exactly 5 gallons and got no reading on my fuel gauge. I pulled the pigtail and got a 80 ohm reading. I then put 5 more gallons just to see what it would read and it went to 39 ohms.

I know my fuel gauge is working correctly as I switch the temp gauge wire over to it and it measured correctly.

Why would it be reading at 39 ohms with it nearly full?

 

[suckerpunched]

I have a note in my files that says the range should be 10 to 70 ohms 10 being full.
I have never had luck with non oe senders reading correctly, ever.
I end up mocking up the sender out of the tank, grounding it to the frame and hooking the sender wire up. with careful measurement of the tank, bending around the sender arm and adjusting it's length, I can usually get it pretty close.

 

[thegreatjustino]

The aftermarket senders are crap. I have a '67 that still has the original sending unit it in. 53 years old and hundreds of thousands of gallons of gas run through it and it still works better than a brand new aftermarket part. You'd think with all the improvements in technology over the past 53 years, such a simple part would be a piece of cake to make work correctly.

 

[Skinnyr1]

I put an aftermarket sender in my aux tank a couple months ago. I worked for two tank fills, and now is sporadic. The reading was always wrong. 1/2 tank was empty. I think the float is now full of gas. If I bang on the tank it will float up for a little while, read, and then sink again.

They are junk.

Does anyone know of a quality sender to purchase? I need the replace the aux tank one again, and the main tank is OE and bad too. I only want to do this job again one more time.

 

[DirtDonk]

So it actually has "0-60" stamped or printed right on the sender Razorback? If so that's odd in itself.
But I did learn just a couple of years ago from some experts here that said there were some non-standard models that came on certain year Broncos. Hard to believe actually, but the experts were not fly-by-night types, but actual "people who should know" types.

That said, suckerpunched is correct with the 10 to 70 (usually written as 70-10) for standard Ford instruments of that era. Ford changed it again in the late '80's I believe.
And even that is just a rounded off I think. The originals were rated at something more akin to 73-9.5 or something odd like that. So you can see why it's rounded off, just like the crankshaft imbalance numbers of 28 and 50 have been.

With yours reading 80 right now, I wonder if it's a standard 70-10 that is out of range. You might have to pull it out and check it through it's full range, and tweak it as was mentioned.
I had to do that with my originals AND factory replacements bought from the Ford dealer back in the late seventies. They were consistent and reliable, but they were mis-matched to the gauge right out of the box too.

Paul

 

[bronkenn]

I have a '67 that still has the original sending unit it in. 53 years old and hundreds of thousands of gallons of gas run through it ...

Figuring 10 miles to the gallon you have well over a million miles on your truck. Does it still have the original engine?

 

[Razorbackbronco]

So it actually has "0-60" stamped or printed right on the sender Razorback? If so that's odd in itself.
But I did learn just a couple of years ago from some experts here that said there were some non-standard models that came on certain year Broncos. Hard to believe actually, but the experts were not fly-by-night types, but actual "people who should know" types.

That said, suckerpunched is correct with the 10 to 70 (usually written as 70-10) for standard Ford instruments of that era. Ford changed it again in the late '80's I believe.
And even that is just a rounded off I think. The originals were rated at something more akin to 73-9.5 or something odd like that. So you can see why it's rounded off, just like the crankshaft imbalance numbers of 28 and 50 have been.

With yours reading 80 right now, I wonder if it's a standard 70-10 that is out of range. You might have to pull it out and check it through it's full range, and tweak it as was mentioned.
I had to do that with my originals AND factory replacements bought from the Ford dealer back in the late seventies. They were consistent and reliable, but they were mis-matched to the gauge right out of the box too.

Paul

Hey Paul here’s the link to it. I thought it strange once I started looking into it as well. I thought all the previous ones I have had were the 73-10 range.

https://shop.broncograveyard.com/mo...d-Bronco-Sending-Unit-Rear/productinfo/10210/

 

[DirtDonk]

Interesting. Notice it says too "plus or minus 10 ohms"? Wouldn't that be 10-75 then?!!!
I don't know where the info came from, but I bet it was inconsistent at best, when it came to implementing that ohm range in vehicles. I'd be willing to be that if some found their way into Broncos it was inconsistent and haphazard.
Perhaps it was installed only in some that needed correction and it was easier than trying to replace the gauge cluster or the single instrument.

I don't know, but there should be a way to tell what your gauge is supposed to see, and to see if you can make yours work with your gauge. As I mentioned, even brand new from Ford my originals AND my replacements did not read correctly with my gauge.
The read consistently 3/4 full when the tank was chock full, and WAYYY below empty when they finally ran dry.
After I got through tweaking the float arm and stops on the sender they read perfectly for me. That was just a needle's width above full when I filled it up, and a couple of needle's width below E when dry.

You may have to do the same thing, or you can try using the normal 10-73 to see how that works. But what you're seeing right now is not even consistent with that (being only 8-10ohms difference).
What does that 39ohm reading with the 10gal read on your gauge?

Being able to read up to 80 on a supposedly 65ohm unit, I'm guessing the stops and arms are just not bent right back at the Chinese factory.
Time to get out the old pliers and eye-ball calipers and go to town.

Paul

 

[DirtDonk]

It could be due to shipping too, now that I think about it.
When we were selling our Sherman tanks, we'd set EVERY single sending unit to work in the proper ohm range before shipping. Unfortunately we'd ship the tank with the sending unit mounted inside already.
To my mind then, the shipping and bouncing around was playing havoc with the pre-set sending units because we certainly had plenty of complaints over the years of them not reading properly with the customer's gauges.

The problem was of course that as we know, each Bronco's gauges and wiring system, after 40 to 50 years, was not very consistent with factory ratings either.
The bottom line was that many of our customers still had to remove the senders and tweak them for their individual trucks, even though we'd set them at the shop before shipping.

Since yours was in a box most likely it did not suffer the same fate. But it's surely out of range just based on your actual measurements.
However, if it shipped installed in the tank, then maybe that played a big part.

Paul

 

[sprdv1]

Yeah. Seems out of range

 

[sprdv1]

So it actually has "0-60" stamped or printed right on the sender Razorback? If so that's odd in itself.
But I did learn just a couple of years ago from some experts here that said there were some non-standard models that came on certain year Broncos. Hard to believe actually, but the experts were not fly-by-night types, but actual "people who should know" types.

That said, suckerpunched is correct with the 10 to 70 (usually written as 70-10) for standard Ford instruments of that era. Ford changed it again in the late '80's I believe.
And even that is just a rounded off I think.

The originals were rated at something more akin to 73-9.5 or something odd like that. So you can see why it's rounded off, just like the crankshaft imbalance numbers of 28 and 50 have been.

l

Good info.

 

[thegreatjustino]

Figuring 10 miles to the gallon you have well over a million miles on your truck. Does it still have the original engine?

https://classicbroncos.com/forums/showthread.php?t=203464

 

[bknbronco]

i got a new sending unit made by dennis carpenter and the float turned to mush and broke into 3 pieces withen a few minutes of me starting to fill the tank. good luck.