Gas gauge ????

[bestchevyfan]

Gas gauge pegs out to the right. Whats wrong ?

[_Ogre]

959 posts and you ask a question without any info on what your working on?
look at my signature for how to put your build thread in your signature

that said...
probably the wire going to your sending unit is grounded to the frame/body/motor
disconnect the wire at the gauge and see if it changes the reading, this will tell if the gauge is working
the disconnect the wire at the sending unit to see if it changes, this will tell you if it's the wire or the sending unit

[67 Burb]

Originally Posted by bestchevyfan

Gas gauge pegs out to the right. Whats wrong ?

Open circuit between the gauge and the sender in the tank.

[VetteVet]

It is always important to give as many details as possible pertaining to a problem but at least the year, model, and engine transmission combination.

I think a lot of guys will post their first messages and give those details then think that everyone remembers what they have. Not realizing that this forum has thousands of members. That's why some don't get replies to their posts. JMO.

That being said:
Most gas gauges work the same way. Power is applied to one side of the gauge and a variable resistance to ground (sender) is applied to the other, with a resistor between to protect the gauge internals.

The variable resistance is controlled by the float arm in the tank. When the resistance is high the gauge reads full and when the resistance is low the gauge reads empty.

Looking at the gauge face, a reading all the way to the right CW would be a full reading and anything past full usually the 3 o"clock position would mean too much resistance to ground such as a broken wire or open circuit between the tank and the fuse panel on the tan sending unit wire. As 67 Burb suggested.

Anything reading full left, CCW, is an empty tank or a low resistance to ground. Usually a shorted sender wire to ground.

Trouble shooting is easy in most cases. With the key on.

Remove the tan wire from the fuse panel FUEL terminal, this should give the 3 o'clock
reading on the gauge.

Run a ground wire from a good ground to this terminal and the gauge should go to dead empty. Key still on.

If you get those readings the gauge is usually good and you can look to the sending unit wire or the sending unit.

Common causes are 1. the tan wire chafes over time and grounds under the sill plate on the drivers side.
2. the tank sender loses it's ground to the tank or the tank loses it's ground to the frame.
3. the float gets pinholes in it and fills with gas keeping the empty reading.