1994 Pickup DLX Extracab 2WD 5spd 22RE. The idle drops when lights are on or fan on and if both lights are on and fan on high it drops significantly (200 rpm). Obviously it is a load on the alternator and that is putting additional drag on engine. Battery is good (good voltage and load tested). Alternator charging voltage good. What gives? Is there a component that triggers idle up when there is an electrical load? I have a factory service manual but can't figure it out. I fixed my AC idle up issue but this is different. If anyone can identify what parts I should focus on in the pics here that would be helpful.

 

Admittedly guessing here but.....
Bad battery ground(s)? Disassemble & clean back to bare metal the battery ground cable terminal to frame/body grounding point. I don't know about the newer trucks but my '78 also has a ground cable going from the cylinder head to the firewall. Clean those two connecting points as well, if you have one of these.
I'd also check the resistance of the ground strap/cable(s) with an Ohm meter. End to end it should read zero ohms resistance if the strap/cable is good & the connections are clean & tight. 0.1 ohms or higher I replace with new.
It's a good idea to check all this anyway, as any of these things if original are now 28 years old, and could be worn. loose, corroded, etc.

Failing voltage regulator? Any major parts store can test it for you for free to know for sure if it's good or going bad. Easy enough to remove it in the parking lot with basic tools.

 

Double Check Charging System Voltages Under your DESCRIBED Conditions.
https://www.yotatech.com/forums/f116.../#post52401963

Check, especially IG voltage. You may be able to probe behind alt connector, OR prick wire with a pin to contact copper inside.

 

Thanks all! Will check all that. It may take me a week or so to get to it.