Electrical Issues - 1990

OK So,

It started like this.
1990 - every option available, power seats, power windows etc. Car has just shy of 250k Km on it. Everything was working fine. I was driving home one night with the heat/lights on. Went to flick on the high beams, whole car shuts off. No interior lights, no engine, no starter nothing. Not even a horn or hazard lights. Went to meet the Tow truck the next day and before the truck got there, I tried it, CAR STARTS. Driving again, 2 weeks later, went to turn the high beams on (as I have tested since original issue and worked fine) and car shut off again. Changed the alternator as I thought I was not charging the batt properly. Changed the Solonoid as well. No luck, sometimes it will start after sitting, but usually not at all. I have no interior lights, no door bell when key is in ignition. If I jump the solonoid with a screwdriver the car turns over but won't start. Thus, I know I have juice in the battery, but its not going past that point. ANY help would be greatly appreciated.

Thanks Guys!

As an update, I went out to the car yesterday after work and got in, lights came on, everything came on. Started the car, it ran for 3 seconds and immediately shuts off again. Will not start, click or have any lights regardless of key position.

Check power cable from battery to fuse panel for corrosion or loose connections.

Try measuring for 12V presense at fuse panel when car is acting up. If you don't have 12V at fuse box, then cable is likely open somewhere.

Corrosion could cause in lower voltage reading - between 0V and 12V and limit total current available (results in dim lights, slow window roll up, etc)

I would check the multi function switch that you're hitting to change to high beams. I had a short in mine and it caused very strange problems, like blowing out the brakelights or turning all the lights off. Replaced and all problems gone.