probably the sending unit. unfourtunatly the sending unit and fuel pump are made in one peice, so expect it to be expensive
In the tank, it's called a fuel pump module.
Check for power and ground to the sending unit . If you have that then ground the sending unit and see if it works.If the gauge works then the sending unit is defective.
If the fuel gauge isn't working on a 1999 Chevrolet Blazer it could possibly be because the float is stuck in the fuel tank. I had this problem when I got my 99 blazer, the float and sensor for the fuel gauge is on the fuel pump which is in the fuel tank to keep it temperature regulated. I had to replace my fuel pump, which ended up going bad on me, and after it was replaced the gauge works just fine.
The oil gauge does not have a reset. Is malfunctioning, the sending unit has probably failed.
try changing the sending unit for the temp gauge
fuel sending unit is bad
you drop the fuel tank and replace the sending unit
Inside the fuel tank combined with the fuel gauge sending unit
Just to the side of the thermostat housing.
Replace oil sending unit with a manual gauge
It is in the driver side head, between the first two spark plugs.
wiil a 1999 blazer engine fit a 2002 blazer