Next to the thermostat housing.
How do you change the oil filter sending unit of a 1999 suburban?
The temp sending unit may be shorted to ground. Unplug the sending unit to see if the gauge drops to cold. If it does, you have a faulty temp sending unit.
Your fuel sending unit is in the gas tank, mounted from the top.
Do you mean the Temp sending unit, oil pressure sending unit, or fuel level sending unit?
It is the two wire sensor next to the thermostat housing.
Which sending unit? Oil pressure sending unit? Engine temp sending unit? Fuel gauge sending unit?
A faulty temp sending unit can do that.
If the wiring and connections at the coolant temp sending unit check okay start with replacing the coolant temp sending unit. Temp sending unit should be less than $20.
The temp sending unit should be found close to the thermostat housing. It will have a single wire attached to it.
What sending unit are you looking for ? Fuel , oil pressure , water temp ?
To fix the temp gauge check the temp sending unit first. A bad sending unit is a common problem with the temp system.