I'm also not a 'mechanical' person, so my knowledge is very limited. But I've been noticing that my headlights/dome light seem to dim when I use the power windows/locks/mirrors and also when I put the car in 4WD, etc... the battery is reading over 14 on the battery gauge in the car, so I don't think it's the battery. Maybe a weak alternator?

Truck is a 96 Blazer LT, but has a '00 4.3 Vortec motor.

 

how dim are we talking here?

 

Have a load test done on the battery!! Try and get the highest cranking battery available for it- Cranking amps and cold cranking amps.. if its the orig battery it prob is wearing out...

 

most the time when you have dimming lights ... if you press the brake pedal and they dim , or fan slows down (when on lol), it is normally the alternator that is starting to go ... it works fine when just driving but as soon as you put any kind of load it drops the amps/voltage by say 2+ volts and hence you get the dimming effect ...

replace alternator with new or junkyard one and should fix problem .. that and clean connections to battery and alternator while your at it!

hope this helps!

 

they dim to the point you can tell someone is using something that needs power...I don't know exactly to explain what you're asking.

 

easiest solution (It should be a free thing if i`m not mistaking) if you live near a sears or autozone or store of that nature go there with the truck and ask them to do a load check on the battery... and do a charging check.. How far down does your gauge go when the lights dim? This may sound strange but someone else here will prob be able to say the same,,, A car will run off battery power for approx 15 to 20 minutes if the alt goes bad........ Try that and see what happens...

 

also an even easier way to test alternator... start truck take neg- cable off battery .. if it shuts off = alt is bad ...

if stays running ... then turn on a load (fan , press brake pedal , and turn on high beams ) if it shuts off then its DEFINITELY the alternator ..

if it doesnt shut off during loads on then its prolly the battery starting to go and has a bad cell in it.

 

btw my truck has same issue with dimming at night when i have headlights on and when i turn on the fan the needle for volts drops to like 9-10volts till i turn it off then goes back up lol... im just gonna get myself a junk yard alt for now .