Flickering Headlights at Very Low RPMs

[Stanley]

I've had this issue since I got the car. I've since installed LED bulbs for the headlights, upgraded the alternator to a 200-amp model, performed the Big 3 wiring upgrade, and got a new and decent battery. At the same time however, I've also put in a new stereo, and I know that alternators are not just measured by their peak amperage but by at what RPMs they can make their amps, and that I don't know (it's a Rare Electrical model), so there's still a decent bit up in the air.

Essentially, when I slow down to almost nothing (say, crawling to a stop at a traffic light, pulling into my garage, I notice my headlights dim down and flicker. I also notice it, I believe, when I hit the initial acceleration coming out of a stop. It doesn't happen while driving normally.

Any clue what I should be looking at to narrow down the cause? Thanks.

 

[Grog6]

what 200A alternator?

 

[Stanley]

This guy here:

New High Amp 200A Alternator 95 96 97 Ford Thunderbird 4.6 Xl3U-10300-Bb 3342250

7776HA, 7776HAB5, Alternator, XL3U-10300-BC, 334-2262, 2L3U-10300-BB, XL3U-10300-BA, XL3U-10300-BB

www.rareelectrical.com

 

[Grog6]

It looks like a 3g; so it probably has the same problem as the original one. Does it have the same connectors?

 

[Grog6]

Either way, no alternator delivers rated power under 2500 rpm. We have a 3x pulley ratio, so 833rpm.

 

[Stanley]

I get that. But while I could be wrong, I'm presuming that it's not going to be worse than the 130-amp stock model in that regard, and I had the same issue with the stock model.

To be clear, I have no idea if it is the alternator. I have no idea what the issue is at all.


EDIT: Sorry, missed your first reply. I'm not sure what sort of connectors it has. What do you mean by saying that it looks like a 3G and thus has the same problem?

 

[Grog6]

Pull the wire connector that is 1 wire, and see if it still flickers. That's the field wire.

 

[Wile E. Coyote]

Are they flickering on and off, or dimming/brightening quickly? I have the later issue on my truck and it's a bad voltage regulator.

 

[Grog6]

Two alternators doing the same thing would indicate a wiring problem. If it clears up when you pull the field wire loose, it's in that circuit; pulling the field loose stops charging, and should light the alt light.

 

[Stanley]

Are they flickering on and off, or dimming/brightening quickly? I have the later issue on my truck and it's a bad voltage regulator.

If I had to pick one I'd say it's a dimming/brightening. I don't get the sense that they shut off, just that they dip down. Where's the voltage regulator in a 97? EDIT: Apparently, it's inside a 3G-style alternator, so I'm guessing that's not it as I have replaced the alternator and had the same problem.

Two alternators doing the same thing would indicate a wiring problem. If it clears up when you pull the field wire loose, it's in that circuit; pulling the field loose stops charging, and should light the alt light.

I'm about to head out on vacation, but I'll check that when I get back.

One question though: I asked for a quote from Singer (figured I'd look into a more reputable brand, and get something more powerful to boot). The guy gave me two sets of options: one that's "128.5MM denso hairpin style (6 phase)" and one that's "138.5MM denso hairpin style (6 phase)": the latter has some overlap with the first set (e.g. you can get a 250-amp model in both pin styles) but costs more and scales higher in terms of amps. The guy knows what car this is going in, so presumably both are compatible, but what's the deal with two different pin sizes apparently fitting the same car?