What would cause a pulsating electrical system on RD28ETi?

I've been noticing an unusual occurrence on my ride recently. I just recently swapped out my alternator/generator (depending on where you are from) and now it seems like the system is overloaded at times and pulsates. For instance, when I turn on the front and rear defrost (electrical), it really seems to bog down. I am not really running any kind of mods that should stress the system that much. I am running an electrical bandage heater on the fuel filter almost constantly because of the winter temps here, I have a Webasto for pre-start engine warming, and 2 LED driving lights which are not used constantly. That is the extent of my extras that would pull on the electrical system.

Any advice would be great. Is there a chance that the alternator is too small? I replaced it with a factory replacement, but failed to notice if the old one was bigger or not. Would a relay be causing this? I'm just not sure where to begin. I didn't notice this happening with the old alternator - just since the replacement. Thanks mates!

Is your battery OK. The alternator usually charges your battery which sits on float between the alternator and the load. Your load draws from the battery. Sounds like the load is drawing from the alternator and not the battery. If you turn the motor off with the lights on do they go dull immediately?. If so the battery is only just working and the alternator is only just keeping it charged.

Personally i think the alternator is probably too small for all the heating stuff your running. Those accessories pull the battery down fast then doesnt have a chance to charge it properly once your finished with them.
Im only saying this because i had a mitsubishi delica with seat warmers, front and rear window de icers, side mirror heaters and a couple of other cold weather bits as they are an import from Japan so set up for their cold weather. I replaced the alternator with one off a starwagon (same thing but not 4x4) but the stock one wasnt big enough and i had to order another. Had a similar deal with whats happening to you

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Thanks, mates. I have a feeling it could be a bit of both. Since I didn't notice it happening before I swapped the alternator, I may throw the old one back on to see if it still does it. If it does, then it's more than likely the battery. I've had it die a couple of times this season due to the extreme cold. Maybe it's not holding a charge like it should. Might try a deep charge cycle to see if that alleviates the problem.