I have a 2001 chevy blazer 4x4, and my headlights will dim and flicker at times. it happens when I slow down while driving in town around like 30 mph. (only while I am on the brakes). all the lights (headlights, dash lights, map lights…) will flicker momentarily. I can also make it happen if I cause even the slightest load like hitting the window close button while they are already closed, or turning on the a/c. the battery gauge shows the alternator is charging and it always starts real strong. I was thinking voltage regulator maybe, but I really don’t know. It doesn’t seem to happen at highway speeds. Any ideas out there?
Which engine do you have? If you have the I6 Atlas, this is a known issue with the A.I.R. pump operating during deceleration and drawing a lot of current. There are several things to check. First, and this may seem stupid, make sure the two battery cables are separated up by the battery. Put a small block of wood between them if necessary to keep them apart. This has actually eliminated the problem for a few people. If that doesn’t work, check the battery grounds at the chassis. Check the A.I.R. pump ground on the chassis. Have your battery load tested at any auto parts store to make sure it has good capacity. If you have the A.I.R. system, then the final issue is that the check valves start to stick which causes the controller to ramp up the power to the pump. The check valve is easy to replace but costs around $85 on-line or $115 at the dealer.
I would check the battery voltage across the terminals with the engine not running. If the voltage is less than 11 volts you may have a dead cell. The battery died on my 2000 Blazer a few weeks ago with no warning. It was starting strong that morning when I went out, a few hours later it was dead and I had to get a jump. I slow charged the battery and it appeared to take a charge. When I checked the voltage, it was anywhere between 6 and 12.5 volts. I replaced the battery and the Blazer has been fine.
Heat kills batteries, the Blazer is more susceptible because of the tight quarters under the hood. This is why the battery has an insulated blanket to keep the heat out.
Check the engine to chassis ground wires. There should be a couple of them. Personally I would one or two more with at least 6 gauge wire. Braided copper strap is the best, but pricey.
I’ve had that several times and turns out to be a faulty alternator/voltage regulator. They test out just fine on the bench but the regulator just alternates too much. The only ones I’ve had any luck with are the AC Delco reman alternators.
thanks for the suggestion, I will look the batteru getting hot since i noticed the heat blanket itself seems to have been overheated (almost like melted/burned fabric). the outer covering looks like it got hot and the insulation is exposed
jason here, I have to make one correction and addition. as far as it happening when i slow down, it will do it not only when I am on the brakes, but also when I just let off the gas and am coasting down. another thing i forgot to add is that when i am parked with it idling the map lights will constantly flicker slightly. I am used to it and forgot about it till now. Don’t know if that helps but we’ll see. I am checking your ideas and will let you know what i discover. Thanks!