Climate controls in '94 LeSabre

I'm hearing a click-clicking sound coming from behind the dashboard passenger side of the '94 LeSabre soon after start-up and the indicator
light on a selector button on the heat/AC controls that is on goes out. If "off" selected, that one goes out; if de-fog selected, that one goes out, etc.; might I have a faulty relay behind underhood fuse panel? How do I check a relay for proper operation? None are marked on underhood bank of eight. Thanks for advice.
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