So, I figured after 54 years it would be best to replace the fuel tank and sending unit in my '66 Coronet wagon. I have had that new tank in and out of there 3 times now and finally today, shoved the 54 year old sending unit back in the new tank. When I try to measure the resistance of the two new senders, it appears that they are of a slightly different resistance than the old one. So...I have two (2) brand new sending units here, neither of which will work with the car. Slipped the old one back into the tank and gage is back working. Any else have the problem with the older stuff? Are there different sending units? Everything I see shows that they are supposed to all be the same?

Welcome to the world of repro sending units. And no you are not alone. The problem is so rampant that a company called Tanks Inc. makes a device called meter match. I believe Dakota digital makes one as well. I have yet to find a S/U that reads correctly regardless of the make/model of car or brand of sending unit. I am sure we have put in well over 100 various tanks and sending units in the last 20 years.

Man...would seem like it should not be rocket science to make something. Maybe even add in an external trim pot or something. Guess I will just run with the old one. Good thing I did not toss it when I pulled the tank

Agreed or is that GREED by our corporate exec's that get the Cr-p made for .10 on the dollar. You want cheap or good?? No have both LOL

I was told by a man much wiser than me that there are only two considerations that automotive OEM's have when buying something. Price and warranty. The cheapest one that will make it out of warranty is good enough.

The problem is not the OEM stuff, it's the repro cr-p that doesn't work correctly out of the box. trying to calibrate them to ready full and empty is typically a time consuming experince that results in settling for a gauge that reads somehwere near
1. full when full, but 1/4 tank when empty
or
2. between 3/4 and full when full, but empty when empty.

It all has to do with the resistance wire used and the number of turns on the board inside the sending units variable resistor. Not rocket science by any means, just cheap manufacturing.
I have the reason and explanation why this is but cannot post it as it is likely too be considered to racial.
maybe when I retire soon I will look into correcting this issue. But how many are willing to pay 200.00+ for a correct reading unit ?

in the repos the resistor wire they used is designed for fords

I have not tried this but the next time I need a sender I think I'm going to buy one of these, remove the resistance unit, and attach it to the stock assembly. I don't know what else to do.

Tanks, Inc. Universal Sender

Use one of these with your existing unit and gauge. They work great. I have found it much easier than fighting the repop sending units

TANKS UNIVERSAL METER MATCH LINKY

Where do you mount these? Up under the dash after you find the gage wire?

You can put it in the left kick panel area. The wires for the sender are right there.

I’ve got one ready to install for this weekend if I can get over this flu. I’ve had the same problem with factory sending unit not matching well either.

I use to design the fuel tanks and the sending units for the proto type tanks for Chrysler for 35 years... I
guess you tend to find that stuff simple for as how many tanks and sending units I built during that
period of time... this was the one for my Rampage and the sender is dead on (for all the factors) like
unusable empty, true empty, 1/4/ 1/2, 3/4, and the total volume for the tank and the amounts designed for