Hello, I have a problem with my alternator. I have a 95 chevy tahoe with the 5.7 liter engine when the truck is running mostly at night, with the heater, radio, headlights or any other accessories being used, my voltage gauge drops extremely low, when at an idle. While driving or revving the engine, it goes right back up to normal. I do not know the age of the alternator, but the drive belt is brand new, and the tension is correct. Also there are no strange noises. The battery is a year old, give or take, and it never goes dead, or fails to start the truck, ever. And there are no warning lights coming on on the dash. This is very annoying especially when everything dims and the heater blower slows down! I just want to make sure before I replace the alternator, that its not something else that I can check first. Please help! I appreciate any ideas!

Thoughts:

. Check idle speed.

. Regulated battery voltage should be 14 to 15 volts:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-10.html#post1973613

It wouldn't hurt to clean the grounds and cable connections going to the under hood fuse box. Apply dielectric grease, afterwards. It may help to increase the AWG going between the alternator and the under hood fuse box. Be sure to also clean the battery terminals and cable connections, applying dielectric grease to all connections.

. Clean alternator connections.

. Replace alternator brushes and clean slip rings, if it's easy.

All my connections are clean and tight, but I will grease them too. What should the idle speed be, just out of curiosity? Haven't checked the regulated voltage yet but I plan to tomorrow. Thank you much! I appreciate it!

I would guess around 700 rpm. Incorrect idle rpm may be the main problem.

Your idle speed should be between 600 - 700 RPM with no loads on.
That alternator is rated at 100 Amps and between 13 - 16 volts.

At idle, the alternator will not be able to recharge the battery nor even maintain it properly. Especially if extreme loads are present. It just wasn't meant to do that.
There are things you can do: consider adding an additional battery, researching aftermarket options like changing the alternator to one built for your running requirements, or perhaps something as simple as changing your alternator's pulley.
Again, research will be your best bet.
But remember: you're asking a lot from an engine/alternator combo that's designed to be off-idle when most of the work is being done.