Hello, I have a 2000 blazer 4x4 4.3l, and I have searched all the posts about flickering headlights and interior lights, which I am having, it seems to do it when the engine is first started. When its cold outside it seems to be worse, but continues throughout the duration of any trip. I have also noticed that the pulsating or flickering has the same rythme no matter if at idle or while driving at any rpm, it always stays the same. I have checked the alternator for AC voltage and it was only 1.2 AC voltage, which I dont think is enough to really cause this problem because if it was the alternator, the pulsating would change with the speed of the alternator. Anyways I hate to repost this same problem that it seems alot of others are having, but I have not found a post yet where anyone has actually found what is causing this. I checked the grounds under the truck at the rear frame and up in the firewall in front of the steering wheel. I've checked the battery also with a quite expensive battery checker that does something like 10 or 12 tests before it give you an answer so I'm stumped, please help.

 

I am not sure if anyone has ever found a concrete reason for this. Could be the PCM not properly sending the charge signal to the alternator or it could be a problem with the alternator voltage regulator itself. It also could be an issue with the battery itself.

 

mines dims with full blast heat or air, or when i push the window switches, got a new alternator and it doesn't do it as bad. it didn't solve it but it is less noticable, i wonder if by getting a higher amp alternator if it would solve it.

 

Checking the signal wire which I'm assuming is the exciter wire to the alternator is what swartlkk is referring to is a good idea! I will check there and post what I find. That makes sense as far as the wavelength of the pulsing not changing whatever the rpms. thanks

 

Yeah, the pulsing could basically be the PCM lagging in control over the alternator. This could happen either due to a bad voltage sense wire to the PCM or something amiss with the voltage the PCM is reading. Any delay in either side of the control will cause a hysteresis effect.

 

Has anyone solved this yet? 2003 blazer 4.3 4x4 same problem.