Well, I found a set of ceramic fuses on ebay and they are en route as I type this.

I replaced the above fuse with another and the A/C worked all day yesterday in 100+ degree weather and auxiliary fans were engaged all day.

Later last night it happened again.

No evidence of a melted or shifted fuse but I'm not impressed with the big round ends on the fuses I got at Autozone. So, I switched it with the pointy-ended one for the rear windows and the A/C works again and both fans engage.

I will be replacing all the plastic bodied fuses once I get the ceramic set in.

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1993 W124 300D
-297K on the clock as I type this.