Gas Guage - wrong reading

I changed the Sending Unit on the gas tank but I don't get the right reading on the gauge.

If I fill up the tank the gauge only goes between 1/2 and 3/4.

Please Help!

There are different senders for regular cab, Cab Plus, and long bed, among others.

Maybe your float arm is stuck on something, did you align it correctly too when you installed?

Is this a new "Mazda" sender or the Spectre aftermarket one?

Cusser - Thank you for the response!

It's an Extra cab. The old sending unit was also new which triggers me to think something else is wrong.

The old unit was reading the same. Yes I made sure the float was working properly before installing.

If the ohms across the sending unit at the empty and full positions are within the specifications in the service manual, then likely a bad gauge or high resistance in the wire to the gauge, or possibly a bad ground connection.

Is is accurate on the bottom end of the range... i.e, do you have approximately 1/4 tank remaining when the gauge indicates 1/4?

There is a voltage regulator for the gauge built into the the speedo cluster... might be that as well. How accurate does the engine temp gauge work? Indicate 1/3 to 1/2 of the scale when the engine is fully warmed up?

Do you have the original speedo cluster? Has it ever been swapped?

Thanks guys! It's a 93 green extra cab. Previous owner had a Rotory in it but end up putting a 2.2 back in.

The cluster looks like the original but I'm not sure.

The Temp gauge reads normal but the speed is off by like 6-7 miles (faster).

Could this be linked?

The speed wouldn't have anything to do with it. If the outside diameter of your tires is much different that stock, then that could throw off the speedometer. Also, since you mentioned it had a rotary in it, if the transmission or rear end was swapped, then that could throw your speed off too.

Here's ohms ranges of the sending unit (all models):

FULL: 1 to 5 ohms
EMPTY: 103 to 117 ohms

Gauge itself:
7 ohms should read full
32.5 ohms should read 1/2 full
95 ohms should read empty

Maybe a mechanic or speedometer repair shop would have resistance tool to check the gauge. Digital multimeter can read ohms resistance of the sender (or sender wires) when disconnected.