pwogaman, NOT! The two systems are indeed different in how they achieve the end result. Yes they are temperature controlled and AC pressure controlled, that is the extent of the similarities. The 88 300 SEL has a blue two pole switch that is mounted in the middle of the cylinder head between the valve cover and the air cleaner assembly. This signal is sent to the AC pushbutton assembly for temperature control. When the predetermined value is met the AC panel activates the K9 relay for high speed fan operation. Low speed fan operation is governed by AC pressure, when the red/green pressure switch is closed due to high pressure in the system it activates the K10 relay.

Quick Tests:

1) Disconnect blue two pole switch-Electric fans should run at high.speed.
2) Bridge red/green switch on rcvr/drier-Electric fans should run at low speed.