Light metre not working

The power button decided to fail while it was sitting idle.

Did you try to de-assemble and clean the contact of this button with contact cleaner, take care to not shoot on rubber parts if you have near the contact, it would blown up !

Check the charger output to verify whether or not you have a bad charger using a voltmeter. These smaller batteries are notorious for having a short shelf life and poor quality control from the manufacturer. Load test the batteries after you verify you have a working charger that will bring the batteries up to the proper voltage first.

It is probably a bad light switch

My daughter had same problem--Saturn dealership replaced the left and right door light switch--these are tied into the antitheft system--Service tech said this is common problem .

Switches are available from autoparts stores and easy to replace-

sounds like a faulty air mass metre or lambda sensor throtle position sensor depending on which year or model id get its fault code read

They're lovely old light meters and there's an online copy of the manual for your exact model at the address below:-

http://www.urmonas.net/manuals/westonII/westonII-1.jpg

Have fun, and please return the favour by rating my answer.

the range from a simple sensor issue with no symptom except a check eng light to a rough idle with a light.

Ditto... except my daughter is 10. Both screens remain black, are fully charged and green light stays on for more than 4 minutes.

Sounds like a short, no way of knowing fwhare for sure till You run a tester the lenght of the wire.