Light & Sound elements not working reliably - suggestions?

[naf]

Mods, please move this post to the correct area if it doesn't belong here. My light & sound sets are in both the space and town themes, so I figured I'd post to the general forum as opposed to a specific theme.

I have several light & sound battery boxes (http://www.peeron.com/inv/parts/4760c01), plate pieces with the built in electrical contacts (http://www.peeron.com/inv/parts/4758), lights, sirens, etc. They've been sitting in a (relatively) sealed plastic storage bin in a basement for the past 20 years or so. I recently dug them out, popped a new battery in, and tried to test them out. I tried all combinations of the 4 battery boxes, with the different lights and sirens, and none of them seemed to work. I took one of the boxes and cleaned the contact area with some rubbing alcohol and a cotton swab. I also cleaned the contacts on one of the lights and siren pieces. I managed to get the lights working, although it is very finicky. You have to press it on just right, and if you nudge it, it'll go out again. Same with the siren, it has to be fiddled with before it'll work.

Has anyone had issues with their light & sound pieces like this, and how did you fix them? I'm assuming that the contacts are just dirty or corroded with age, can someone suggest a cleaning product to use in order to restore these pieces? I'm afraid that certain cleaning products, like the electrical contact cleaner you can buy at Radio Shack, might discolor or damage the plastic.

[JopieK]

First suggestion: use a multimeter and see what is going on. Second suggestion: use rubbing alcohol to clean contacts, it won't damage the LEGO.

[naf]

Tested with the multimeter, and all of the battery boxes seem to be in working order. I gave all of the metal contacts a good scrubbing with rubbing alcohol, and they seem to be working much better. The lights still have some problems at times, probably just need to keep scrubbing a few more times.