A Puzzler from the Final Frontier

RAY: This is from the wonderful world of space travel. This puzzler
was sent in by Dave Foster. I actually had to obfuscate a little, but
here it is:

In the early '60s NASA was sending electronic gear into outer space
on unmanned missions. They'd already sent a guy into space but they
wanted to make sure that if they were going to send people up for
longer flights, that they had a chance of surviving. They were
sending this electronic gear up to test a variety of things like
radiation exposure, and so on.

The equipment kept failing, but they couldn't figure out why.

Finally, someone determined that the circuits were overheating, so
they installed a fan to cool off the devices.

But the problems persisted. Why?

Think you know? Drop Ray a note!

[ Car Talk Puzzler ]