1992 400E Aux Fans; root cause help requested

[400E_FAN]

As the temperatures have gotten warmer out here in Massachusetts over the past couple of weeks I have noticed that the aux fans were not kicking on at 105-107C
the temperature would continue to climb to 150-180 if I did not turn the heat on high.

Anyway, I have printed out and read nearly all the posts related to this problem I cannot find the answer to what I am encountering...so perhaps someone can help with advice...

-checked to see that aux fans work by disconnecting the Coolant Temperature
Sensor...Fans kicked on fine so I figured that I had a bad CTS.

I replaced the CTS but the problem does remain

-checked fuses -OK

-checked relay operation -OK ( I can hear it click on & off with ignition key in ON position)...No resistor in the high speed relay on my car that I can see.

-checked low speed resistor (under ABS control unit) -OK (But even if this was
bad it should not affect high speed fan operation when temps go up beyond 105C
right?)

-checked switch on top of receiver dryer -OK (Again, this is for low speed fan
so should not affect the high speed kick-on right?)

What have I overlooked?