Take the whole alternator back where you got it.

It could conceivably be a regulator having a short brush just skipping over a poorly turned set of slip rings, but brushes are one of the few things these rebuilders actually do replace routinely.
--
Art Benstein near Baltimore

Yogi used to work with the Yoo-Hoo soft drink company. A woman once called and asked if Yoo-Hoo was hyphenated. Yogi said, "No, ma'am, it's not even carbonated."

That happens when, e.g., the voltage regulator is pulling in and out. The battery moderates some of the fluctuations, but under a heavy load it causes enough voltage fluctuation to be noticeable in your lights.

Put a (preferrably*) analog voltage meter across your battery when the car, idling, has all its accessories (lights, fans, rear defroster) turned on. You should see swings in voltage synchronized to the "strobing".
[ * a digital meter may not show the swings as well.]

I'll bet you got a rebuilt alternator, done by a local shop. They probably cut some corners in the rebuild, or reused an old voltage regulator.

I agree with the other posters of what you are seeing.

It seems you are describing what you would see in a motorcycle headlight. They do it more extremely to get attention of drivers ahead of them.

I think (have no facts) those bikes are wired in a way to pick off the output power from two phases of the windings or use a pulsing device(?) and feed it to the headlight, bypassing the battery supply during daylight running.

It could be a bad connection internal to the alternator or from the from the exciter wiring. It is the little wire on the alternator and serves as a feed back circuit from the systems circuit voltage, on two wire alternators.

The regular pulsing indicates it very well maybe be setup by a “going out” regulators own internal circuits, but then again.

The brushes inside the alternator can be "hopping" due to a bad rotor or fit up to the slip rings. This is rarer but can happen. This stuff can take out regulators.

Worn out and under sprung brushes create some arcing that results is unstable conduction. It’s why they are sold together when the regulator has to be replaced. Also for those that don’t know how to load brushes for soldering. I change mine about every 80,000 miles for .50 a piece because I’m cheap and they are too!

After you do just one brush of a set, it appears it’s always the “second one or second set of things” that become the easiest. Must be a “nature” thing!

Explains to me, why other countries are jumping ahead because they haven’t had to do the first step and then look at things that have already been done for them. Fresh eyes and minds with better refined tools!

Anyhow, all of this becomes most noticeable under heavy loads. That is why you check the condition of your alternator output voltage to the battery with some type of load in progress. A steady meter reading with spread of 13.2 to 14.6 specifications is required for good system health. The reading in this range depends on the state of charge of the battery at the beginning and “all” the connections to and fro. A good battery is like a reservoir or shock absorber for the system. It may just sit there but it’s a very active device!

Should you not find a problem on your car I would have it spun at you local auto electric shop or parts house. Possibly it is a bad rebuild.

Good luck
Phil

I recently had this exact problem on our Isuzu Axiom. The dash lights, map lights & headlights would pulsate at idle about 750 rpm. Above 1000 rpm it would even out & go away. I had the alternator tested at Oreilly Auto Parts during daytime. Battery, alternator field diodes & regulator all checked okay. Alternator output was about 14.4 v. Then I turned on all headlights, fan, ac, rear window deice and radio to put full load on the system. The output started fluctuating between 13.2 to 13.5 v immediately, telling me the regulator was going bad. I replaced the alternator & all is well.
Even though your alternator is fairly new you might want to test it. There are a lot of bad ones being sold!
Sorry for the long post... hope this helps!

Good Luck!

Hello,


You would be wise to check the diode bridge inside of your alternator. However, since requires the disassembly of the alternator, it may be easier to substitute a known working assembly.


Goatman