My fuel low level light never works
My seat belt light works intermittently

The gauge for the fuel reads correct

What or where is the problem so I can fix it ?

 

Cold solder joints in the idiot lights. You need to take it apart and remove the old solder, and redo them.

 

Possibly, but that'd be the second thing I'd check.

The seat belt receiver has a connector at the base that's prone to dirt/water/general crap intrusion...check it (both sides) and clean as appropriate.

LOW fuel is- just like the fuel gauge sending unit- a ground, so it's easy to check.
Key ON, with the gang connector at the fuel tank bulkhead undone, run a jumper from the low fuel wire to ground. Essentially, you're duping the sending unit function, if the warning light comes on, the in-tank sender is bad.

If the light doesn't activate, you check the cluster solder joints (assuming it's not just a bad bulb) but keep in mind you could still have a bad sender as well.

I've had to redo the solder for the clock three times (because I suck, apparently) but the other joints in the cluster have been fine so far (and at twenty years, I wouldn't complain anyway).

 

s4: pages 15-170 & 15-171 in the FSM
s5: page T-46

s4 & s5 fuel warning connectors are identical. Buckle switches are identical. Seat belt warning connectors are different.