If it's not the alternator?

[IFallsRon]

A couple weeks back the headlights started to flicker (and the dash needle jumps up and down) in the morning on my 88 Silverado. I figured it was the alternator going bad so I pulled it thinking the parts store would replace it but when they tested no problems showed up.

After the engine warms, the problem goes away. I'm wondering if this is a sign of a bad cell in the battery.

My next step is to get the charging system tested but I haven't had the time for that yet.

[Scott K]

I would start with getting the battery and charging system tested. Most places will test it for free for you, or a minimal fee.

[sparcebag]

Not sure but is there a voltage regulator on that 88? I'd check it.

[Scott K]

I believe the voltage regulator is internal to the alt, so it should have been tested.

[Jeremy airjer W]

Make sure the terminals are tight and clean! I have had corrosion/acid go through the positive cable and start eating away at the starter where all the fusible links are, a couple of times now. both of them have been side terminal batteries.

The flickering lights are real common on caravans. the simple fix or start is to replace the battery.

[Kodiak]

did you get the alternator tested? my car was doing the same, so i replaced the battery and it ended up being the alternator.

[BobT]

It's interesting that you indicate that it improves once things warm up. What's the condition of your belts? I don't know if your model year uses a single serpentine or if it uses v-belts but my 85 Ford still used v-belts. They could be getting old, hard, and cracked like me and when you first start it cold they could be slipping. You may not even hear them squeal although I've been known to do that from time to time.

Once things get going the belts get heated up and soften and then begin to work better.

Bob

[IFallsRon]

The alternator and battery both checked out good. The belt and tensioner are pretty new, too. I cleaned the battery and cables. This weekend I'm going to check the other ends of the cables.

Looks like time for a trip to the auto electric place to get the entire system checked.

The past couple days, the battery light has come on and there seems to be no power from the alternator for maybe a couple minutes. But the power kicks in with an occasional blink then back to normal.

[Macgyver55]

A defective alternator can show up good on a test bench and bad after heating up. A poor connection on a solder joint can cause a flicker but still show enough output to "pass the test". Heat is a big factor with electrical parts because of resistance and the ability of metals to move when heated. The same holds true for batteries