2000 buick lesabre fuel gauge acting erractic

Page 150 onwards of the owner manual covers the heating.

The digital gauge is giving the temperature of the coolant in the block. The normal, standard analogue gauge have the optimum at halfway and overheating is shown as being above that.

https://www.manualslib.com/manual/230789/Buick-2000-Lesabre.html?page=163#manual

Page 133 and 134 in this manual show the standard temperature gauge. 160 shows Climate Controls in this one.

https://cdn.dealereprocess.org/cdn/servicemanuals/buick/2001-lesabre.pdf

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The proper way to find the problem would be to pull a plug wire an see if it has spark or hook up a fuel pressure gauge an see if it has fuel pressure . Don't guess an just replace parts if you don't know how to test correctly .
https://www.youtube.com/watch?v=EB-hVxk4yus

Probably corrosion in connections from sensors to the dash circuit board. Could be components in the dash circuit board.

You may have a unique problem!!! Normally I would say it is the sending unit- in the fuel tank!!!! But Buick LeSabre had a weird thing happen from time to time. Look closely at your fuel guage and focus on the PIN that acts as a stop for the fuel guage to not go beyond the Full mark. Make sure the pin is on the correct side of the pin!!! Sometimes the needle will somehow jump the pin on "E" or "F", and literally hold the needle in place.

fuel level sender in fuel tank

I would start with checking the fuel pressure with a gauge.

CHECK FUEL PRESSURE SOON AS ENGINE SHUT OFF.HOOK UP FUEL PRESSURE GAUGE SEE IF YOU HAVE FUEL PRESSURE.DO THIS WITH IGNITION OFF.IF FUEL PRESSURE 0 THEN YOU KNOW FUEL PUMP FAULTY.IF YOU HAVE 41 - 47 PSI. YOU HAVE IGNITION ELECTRICAL PROBLEM.COULD BE IGNITION MODULE.CODE SCAN CAR FIRST BEFORE BUYING NEW PARTS.

your gauges need to be replaced it sounds like you have a bad mother board on it.

find fule gauge sender on tank,, pull off wire and short it to chassy,
fule gauge should then read full !!! if it dont its a fult in the wireing harnes

Access via trunk, remove carpet and find inspection cover, remove to access fuel level sending unit which is attached to the fuel pump.