Auto Meter Fuel Gauge in 69 Charger

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Mike337

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I want to install an Autometer Fuel Gauge in my 69 Charger but do not know if the original type gas tank sending unit ohms range is compatible with the gauge.

Can anyone confirm if the stock sending unit falls within the 10 (Empty) to 73 (Full) range?

Thanks Mike
 
Copied this from the Web.
The 1969 Dodge/Chrysler gas gauge sending unit varies it's resistance between 8 ohms to make the gauge read empty and then go up to 72 ohms to make the gauge read full.
 
Kendog 170 said:
Copied this from the Web.
The 1969 Dodge/Chrysler gas gauge sending unit varies it's resistance between 8 ohms to make the gauge read empty and then go up to 72 ohms to make the gauge read full
Click to expand...
This is backwards.

The guage are thermo electric, the lower the resistance the the hotter the heater in the gauge gets, the more the needle moves as in full.

The higher the resistance the lower the heater gets the less the needle moves, as in empty and the same reason the needle sits at or below E when the key is off.

10 = full
23 = 1/2
73 = empty

It's not linear and your guage will not read correctly with the stock sender. I do know if autometer makes a specific sender for our cars. To match their gauges.

Also in the Factory Service Manual it outlines the test procedure and the ohm range for full and empty with a +/- range. Free FSM mymopar.com

 
Thanks Guys!

The literature from Auto Meter indicates that the Ford/Chry compatible gauge is designed to work with sender resistance of 8-12 (Full), and 73 (Empty).

Your answers seem to indicate that the sending unit falls within the same range, so it looks like it should work.

3-14-2025 8-48-37 AM.jpg
 
You may find it is not accurate, as mentioned, the sender is NOT linear, meaning, 1/2 tank is NOT halfway in between the max and min.

HOWEVER there is a little toy called "meter match." There are also others, china, ebay, etc, do some research.

MeterMatch Fuel Gauge Interface Module

Tanks, Inc. manufactures fuel system components and polyethylene, steel and stainless steel gas tanks for street rods and special interest vehicles.
www.tanksinc.com

The HUGE issue is that nobody seems to make and sell a "like OEM" sender. Evidently the taper or curve of the resistance of the replacement senders is WAY off
 
I used a meter match on mine. It works great. There a lot variables in the system and you can “tune” most of the mismatches out with the meter match. I think Dana67dart posted some nice graphs awhile back that I stole to program my meter match.
 
Kendog 170 said:
Copied this from the Web.
The 1969 Dodge/Chrysler gas gauge sending unit varies it's resistance between 8 ohms to make the gauge read empty and then go up to 72 ohms to make the gauge read full.
Click to expand...
Sorry for the mis info. Just reading this now.
Cant believe everything on the Web obviously.
 

I bought an autometer gauge thinking that it would work well with the aftermarket senders which a are linear. I never got to try it.
 
There is a lot of misinformation and amateur fixes out there for fuel gage issues. Trying to get 50 year old parts and wiring working correctly is a challenge even if you have the right ones.

One of the biggest issues with getting the gauge to read correctly is the shape of the fuel tank. If you look at it closely, you will notice that the top part has a big section of it cut out to clear the spare tire. This means that the top half of the tank holds much less gas than the bottom half of the tank.

This means that the tank level will drop really fast on the top half because there is only a few gallons of gas up there. It will drop slower on the bottom half of the tank because that is where most of the gas is.

So if you you have a “linear” sender (one made for a tank that is a “box” (doesn’t have the spare cutout), it won’t work right because it is measuring only the level of the gas in the tank, not how much is gas is left in the tank.

No amount of bending float arms or repositioning senders will solve this issue.

In a non linear sender, the resistance only changes a little at the top or the tank because there is only a little gas up there. It changes a lot at the bottom of the tank because there is a lot of gas down there.

Once you understand this part, it will be easier to problem solve to get everything working properly.

This is the problem the meter match solves.
 
Mike69cuda said:
So if you you have a “linear” sender (one made for a tank that is a “box” (doesn’t have the spare cutout), it won’t work right because it is measuring only the level of the gas in the tank, not how much is gas is left in the tank.

No amount of bending float arms or repositioning senders will solve this issue.

In a non linear sender, the resistance only changes a little at the top or the tank because there is only a little gas up there. It changes a lot at the bottom of the tank because there is a lot of gas down there.
Click to expand...
AND the thermo-electric gauges in your cars has a curve too. 23 is half, 73 is empty and 10 is full, if they were linear 41.5 would be half. The sender has to be designed for tank shape AND gauge requirements. It very complicated, but simple at the same time!
 
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