Corolla stalls w/electrical load

[dieselpower300]

My 91 Corolla died yesterday while driving to work. After getting the car towed home I discovered that the car will start & stay running as long as there is no electrical load placed upon it, i.e. lights on, wipers, defrost, heater, etc... even the brake lamps, when ANY load is turned on the cars dies.
Now obviusly it is able the handle the current demands of the fuel pump, but like I said once any other accessory is turned on the car dies.

I removed both the alternator & battery from the car and had each checked at two different places, and both check out fine.

If it was a short, some where how could it effect each of these independant circuits (lights, heater, wipers, etc...) and why would it not effect the fuel pump circuit??

No blown fuses, alternator belt is fine.

Would it make a difference to have the alternator checked while it is in the car as opposed to out of the car?

TIA
Brett

[zdude]

check the alternator when it is in the car. i should be pumping out around 14.2 volts. any less than that and its shot. any more than around 16 and the battery is shot because it has to work extra hard to keep it charged. also check grounds, a little corrosion can not allow enough current to go through, just enough for the pump and spark. clean the battery terminals and have the alternator checked while its in the car