I bought a sender last year at Carlisle that was claimed to be compatible with Mopar ohm range (69 'Cuda). Well, they were full of S-it. With an empty tank (new tank) it reads 3/4 tank. I bought one of those gas tank sender adjusting modules from Speedway and it won't work correctly either. On top of that the gasket for the sender leaks and the new grommet for the filler tube leaks. Are all these companies that incompetent? So, now my question, who makes the correct sender for Mopar gas gauges? I've heard the ohm range is between 10 & 73, is this correct? Thanx for any help.

Have you tried bending the float arm to readjust the reading?

My son has bought a few of those senders, seems like everyone sells them but they all come from the same place.
He's bought 2 now for 2 different c body wagons but I lucked out and found him an nos one last year at the CMC sponsored swap last spring and what do you know... It works and works right.
The ones he bought for the wagons as well as the ones in his ramcharger and 80 pickup both read empty when they really have 1/2 tank. JUNK

There used to be a guy in Ohio (John something?) that rebuilt original ones and from what I'd heard every body who had used his services was happy with the results.

Specializing in the resto / repair for classic cars for ~25 years I have lost hundreds if not thousands of hours fighting the issue across all makes and models. The compensator made by Tanks sometimes will resolve the issue IF your close (within 1/4 tank). Several years back Spectre said they were going to resolve the issue but gave up. Myself I don't understand why it is so difficult. They will OHM out correctly on the bench, and in and empty tank flipping it upside down for full. In the car with fuel, usually have to settle for being off at full or empty. I have chosen to read 3/4 when full and empty when a gallon or two is still in the tank.
I'm beginning to think it may have something to do with the buoyancy of the float, possibly coupled with today's fuels or weight of the arm

The short answer is to seek out an NOS MOPAR sender and pony up with whatever the seller wants if you want a gauge that works correctly.

You might want to call Kramer Auto. I bought might from them about 5 years ago and still reads good. At that time, they recalibrated and made sure it worked before shipping it out. You have to call them because some of the sending units are not listed.
http://www.kramerauto.com

I've dealt with Jim Kramer many times, I actually bought my 'Cuda from him. He's a great guy and honest, but it seems a little hard to get in touch with him lately.

I didn't know they did that .

I'm pretty decent at electricical. I've had this same issue on my wifes 67 jeep Gladiator. New sender ( 2 different styles) read correctly out of the tank when hooked up to the truck harness. It appears to read correctly when installed disconnected from the truck harness and checked with an ohmeter. I have an adjustable resitance box. When I connect that to the harness at the tank, the factory gauge the gauge reads correctly. I ran new wiring from the sender by passing the cluster connection directly to the gauge. The result? it reads 3/4 at full, still has plenty of fuel on E. Doesn't make any sence to me.
Doug

same thing happened to me when i installed a new stainless sender/pickup in the replacement tank i installed in my charger.
i checked the resistance of the sender before installation, and it was spot on. just to insure it had a good ground for the sending unit, i soldered another wire from the sender case to the pickup tube inside the tank, then soldered another wire to the outside pickup tube, to ground to the body sheet metal in a newly drilled hole. however, once installed it reads all over the place. i have never seen F, and a couple of times when it said E, it only took 5 gallons to fill the tank !
the original, super rusty sending unit read almost 3/4 of a tank when it was replaced, and i drained out almost 15 gallons of "weed killer" from the original tank.

Has anyone tried swapping the float resistor from an original one into one of the replacements ?

Not easily done as the resistor board / connections are riveted and the wire is quite fragile. Good thought though.

Mine reads about like what is described here. 3/4 on gauge when full. Empty means you have like half a tank. Has anyone tried bending the arm to compensate? This sender was in the car when I got it, no idea where it came from. I’m guessing this car was gone through in the 00s.

My last car was pretty good, read 7/8 when full, empty was empty. It seems to have been rebuilt in the 90s

plus, the float resistor is spot welded to the pickup tube. [at least mine is.] you would have to be extremely careful removing the float resistor from the new assembly, then you could silver solder the original float resistor to the stainless pickup tube.
and being a charger with the big side hole the filler tube goes in, i installed the sender when the tank was out and lifted and lowered the float arm while checking the resistance. [this checked out almost spot on at full and empty, and the dash gauge read real close to what it should at full and empty.] i figured everything was good to go, but when the tank was installed, the dash gauge ain't even close in operation, although a couple of times it did read full when the tank is full. yes, the tank and sender are both grounded well, with multiple ground attachments.
i'm wondering if the float [which is brass] is no good. however, that would not explain why the dash gauge reads full, occasionally.
it is rather irritating to be sure !

Bingo. This has been my experience as well.

Yep this is what I normally experienced with Spectra or whatever brand other than Mopar. I never pushed it when it showed empty but I knew there was several gallons left.

Theory on why senders read full during a dry test vs actual use.

We're adjusting the senders and assuming the float will reach the top of the tank.

We're forgetting about air space above the fuel and the fact that the float won't touch the top of the tank in operation.

If someone is in this process, try setting the float for an inch gap from the top of the tank.

Why do you believe there is air space at the top of the tank? IF the filler neck on say a 68-70 Charger is full of fuel, how could there be an air space ?
I'll refer to my earlier post #3227987 for my thoughts

Has anyone had success using a device like this inline to compensate for their incorrect aftermarket sender/factory gauge? I've heard from some that they work, and others that they do not.

Basically an adjustable resistor I assume?

https://www.tanksinc.com/index.cfm/page/ptype=product/product_id=748/mode=prod/prd748.htm

"Why do you believe there is air space at the top of the tank? IF the filler neck on say a 68-70 Charger is full of fuel, how could there be an air space ?"



i have screwed up filling up my charger till the fuel ran all over the quarter, and out the vent line [which dumps into the frame rail] making a real mess.
i don't think there was any air that time. [sure stayed on full for long time.]
however, that was tons of years ago, and i'm super careful these days filling it up.
also, the mess was during the time i had the original tank and sender in it.