Swapped the two fan relays (the two on the right) today
for two from the same slots on a '92 Park Ave..
Fans still always on, even when dead-cold.
The skewed coolant temp sensor theory sounds plausible, because there'* no SES..
Not to sound stupid, but this being my first 3800 - Where is the coolant temp sensor?
Is it the item under the throttle body with the wires running from it?

Excellent pic!

Thank you

I went ahead and replaced the coolant temp sensor, as I found the plastic part of mine to be cracked.
Cooling fans still roared to life on cold start..

Then swapped out the two cooling fan relays, no change..

Turns out a friend of mine has an OBD scanner - No trouble codes found.
We then fired 'er up to get some readings while it was running-
All was well, everything was within parameters.

It had been running a few minutes when he pointed out that the engine was operating in Open Loop.. Just few seconds after he said that, it switched to Closed Loop. I noticed that things got quieter underhood..
The fans had shut off when it went into Closed Loop.

We kept 'er running and waited as the coolant temp increased - At about 219 (as I recall) the fans kicked on (both, running at what seemed to be low speed). After they had run a few minutes, they kicked off at about 214 (as I recall).

Apparently when the car is first started and the engine is cool, it operates in Open Loop for a few minutes until warming up a bit, then switches to Closed Loop. The fans must run on High when in Open Loop, then operate normally as it enters Closed Loop.

odd.... i've never seen fans act that way based on fueling...