Very Good ..
Be aware that these mentioned test are for his 124 chassis...you do not mention a chassis, so don't do these test if you have a different chassis.

It is quite common for a fan fuse to blow and the owner never noticed it b/c the aux fan just was not called for...they do not run all the time ..the high will only have a demand when the coolant temp reaches 105C and the low only gets a demand when the a/c high side pressure gets dangerously high ... That is why they are AUX FANS, They come into play when a taxing condition presents itself. A quick test in your case is to simple turn key ON and pull the 2 wire connector off the blue sensor on the termo housing...that will default the ACC Panel to High Fan, verifying that circuit as OK.
Low fan circuit test is to jumper the High pressure sw pigtail wires at the AC reciever drier.
The part that confuses DIYers is the fact that these fan circuits are completely independent of one another, with the exception that they share the same fan motors ..otherwise, they have their own relays, sensors , wiring, fuse , etc and have to be diagnosed as seperate circuits, b/c they are .

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A Dalton