1990 Toyota Corolla - Driving home two nights ago and lost radio and dash lights and engine power gradually waned to just barely above idling. After pulled off the road and parked, only electrical was to dash warning lights (battery etc) and to interior dome light when opened passenger side door. When turning ignition, no clicking sound like with a dead starter. Any thoughts?

it is the alternator or the regulator. get parts store to swap out under warranty.

Combination of brake and battery light mean the alternator is not charging. after you wait for a wile the battery recover some power and will run again but as soon the power drop below 9V the engine die. Test the charging system and replace the alternator
Good Luck

IDLE SPEED COULD BE TOO LOW.IDLE SPEED SHOULD BE 800 RPM. IF IDLE SPEED TOO LOW AND ENGINE NOT WELL TUNE UP AIR CONDITIONER WILL PUT LOAD ON ENGINE CAUSE ENGINE OVER HEAT AND SHUT OFF.

which fuse did you check. verify the wiring to the radio than comes from the light switch to the radio. if all this worked before , then it has to be work that you have done. the only link from the light switch to the radio is for inst panel dimming. first disconnect that wire and ck fuse for tail lights. make sure there is power on both sides of the fuse, use a test light.

spark plugs? spark plug wires? coil? if it shuts off when hot, and starts when cold, coil could be problem....could be radiator stopped up causing it too heat, and will go off wait a few and it'll start back up...

1990 Toyota Corolla Stereo Wiring Diagram

Radio Constant 12V+ Wire: Blue/Yellow
Radio Switched 12V+ Wire: Gray
Radio Ground Wire: Brown
Radio Illumination Wire: Green
Radio Dimmer Wire: N/A
Radio Antenna Trigger Wire: N/A
Radio Amp Trigger Wire: N/A
Front Speakers Size: 4′
Front Speakers Location: Dash
Left Front Speaker Wire (+): Pink
Left Front Speaker Wire (-): Purple
Right Front Speaker Wire (+): Purple
Right Front Speaker Wire (-): Light Green
Rear Speakers Size: 4′
Rear Speakers Location: Rear Deck
Left Rear Speaker Wire (+): Black
Left Rear Speaker Wire (-): Yellow
Right Rear Speaker Wire (+): Red
Right Rear Speaker Wire (-): White

You probably have a bare wire at the back of your car that is shorting out on the frame, or against another bare wire.

1990 Toyota Corolla Car Stereo Radio Wiring Diagram.
Radio Constant 12V+ Wire: Blue/Yellow
Radio Switched 12V+ Wire: Gray
Radio Ground Wire: Brown
Radio Illumination Wire: Green
Radio Dimmer Wire: N/A
Radio Antenna Trigger Wire: N/A
Radio Amp Trigger Wire: N/A
Front Speakers Size: 4′
Front Speakers Location: Dash
Left Front Speaker Wire (+): Pink
Left Front Speaker Wire (-): Purple
Right Front Speaker Wire (+): Purple
Right Front Speaker Wire (-): Light Green
Rear Speakers Size: 4′
Rear Speakers Location: Rear Deck
Left Rear Speaker Wire (+): Black
Left Rear Speaker Wire (-): Yellow
Right Rear Speaker Wire (+): Red
Right Rear Speaker Wire (-): White
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If there's really no spark from the distributor, perhaps there is water in it? WD40 used to be the favourite treatment for these things, didn't it?

I think thats a Toyota issue we have had two corollas and both did that.