I found the source of the ticking sound coming from the glovebox area of my '90 DeVille. I could feel the relay pulsing when it "ticks". The ticking sound corresponds to the clock, HVAC, and Fuel Data Center lights flashing off and on, which is my primary problem.
This relay has a mini-wiring diagram on it; circuits 30, 85, 87a, 87, and 86.
Can anyone identify these circuits? Is this relay a dealer-only item? Expensive to replace?
Thanks in advance.
Matt

You should be able to buy a relay at any auto parts store. They are not expensive, but it sounds like it is working. Something is pulsing current to it.

30 should be constant power, 87/ 87a is the control circuit and 85/86 are the circuits that the relay switches power between. Yes, they can go bad but if it is clicking on and off something is telling it to, like Ranger said. Usually when they go bad they either don't click at all or they click but won't work because the internal terminals are dirty.