91 CRX Idle

I am having issues solving an idle problem that has been plaguing me for some time now. After I start my car and let it warm up (about 10 minutes) the tach needle drops to zero. It idles fine during startup about 750 rpm. The car never stalls, but under high electrical load...fan on, lights on, rear defrost on, 4-ways on...it really bogs down and feels like it is going to stall. So far this is what I've done to try to resolve it:
-New plugs, wires, fuel filter, air filter
-New Distributor...I thought it may be the ignitor
-New EACV
Could it possibly be the alternator? I am running out of ideas. Any comments would be helpful. Thanks

You can have your alternator checked for free at Advance Auto or some place like that. You may have a vacuum leak in one of your hoses leading to the intake manifold. Maybe try adjusting your idle screw. I know the manual says 750+/- but that seems low. Maybe bump it up to 900... it won't hurt.