Hi SAFC,
Be sure that you're at the correct spot -- it's at the back of the junkpile, above and just to the left of the train-top.
After the sensor glows and you left-click on it, Crispin will say "Hey, you found something". It's now labelled as "power source".
Then pick Crispin up from your dropdown top bar (*not* from where he's at on the main gameplay screen) and click him on the power source.