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Headlight flicker on my 2000 S10 ZR2

just bought a 2000 ZR2 last week, great truck with the 4.3L vortec motor, first thing I noticed is the fuel gauge doesn’t work properly, reads full most of the time, occasionaly the low fuel level indicator light comes on and it shows empty, never between full and empty, always one or the other. the guy I bought it from says the motor has been replaced with a GM long block and the fuel gauge problem may be connected to them replacing the motor, bad connection/short. this leads me to beleive that the headlight flicker may have the same diagnosis? I’ve only driven the truck 3 times after dark and the flicker isn’t bad but it is noticable, last night I noticed that the interior dash lights have the same flicker, it’s very intermittent, lasting maybe 10 seconds and not at any specific time such as when I hit a bump in the road or turn on the heat/AC, Weird? so I pull up in my drive last night and my truck is pointing at the garage door, headlights on and when I come to a stop the lights dim slightly, instantly I think alternator, I give the truck a little gas and the lights get brighter. I’m wondering if the problem could be limited to the battery/alternator or is there something I’m missing, I don’t see how this could be linked to the fuel level gauge and maybe it’s not??? that’s why I came to you guys, I’ve listened for the past year now and i find you both to be amusing and informative, thanks for your help

Usually when lights flicker on a vehicle it means one of two things. Either the brushes and springs in the alternator are worn where the brush leads are now in contact with the slip rings, or a diode in the alternator is failing. In either case the alternator probably requires replacing.

As far as the gas guage? It sounds more like there’s a problem with the sending unit in the tank.


It could all be related, and the principal suspects are the Alternator and the Battery, both together. If the lights are getting brighter when you accelarate, that is a clew that there is a problem with your charging system. Hve them both checked out and find out how old that battery is. If it’s around 3 or 4 years, start thinking of replacing it. That is about the life expectancy of most batteries today.

The sending unit is part of the fuel pump assembly, to fix the sending unit you have to replace the fuel pump. The fuel guage on my 2000 S-10 Blazer stopped working a year ago. I just fill the tank each time and keep track of the mileage. I go about 240 miles between fillups in the winter, around 260 in the summer.

Because of the tight engine compartment the battery only lasts 3 to 3.5 years because of heat. Your battery should have an insulating cover on it to protect from the heat. If the battery is low on charge (12.1 volts or lower) the truck will start acting up (ECM related?). In my case the truck was idling high (750 - 800 rpm instead of 600) and the torque converter lock up was not engaging. I don’t know if this is related to the flickering lights, but have the battery checked just in case.

Ed B.

Thanks for the info guys, I’ll track down the charging system problem this weekend, hoping it’s the battery! most of the engines I’ve built are SBC with the one wire alternator so I’m not sure where to start testing on this particular alternator, however I think I can have it tested without removing it??? as for the fuel gauge, I’m going to take the advise from edb1961 and calculate my MPG, I’ve replaced a couple of the in tank style fuel pumps and thats a picnic I don’t wish to be invited to!

Check inside the protective boot of the positive battery terminal. There are two ring terminals and corrosion often forms between them, causing electrical gremlins of various types.